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All questions of Power Plant Engineering for Mechanical Engineering Exam
1 kg.m is equal to- a)9.81 Joules
- b)421 Joules
- c)427 Joules
- d)102 Joules
- e)539 Joules.
Correct answer is option 'A'. Can you explain this answer?
1 kg.m is equal to
a)
9.81 Joules
b)
421 Joules
c)
427 Joules
d)
102 Joules
e)
539 Joules.
|
Baishali Bajaj answered |
You can view more details on each measurement unit: kg-m or newton-meter The SI derived unit for torque is the newton meter. 1 kg-m is equal to 9.80665 newton meter.
On Mollier chart, flow through turbine is represented by- a)horizontal straight line
- b)straight inclined line
- c)vertical straight line
- d)curved line
- e)none of the above
Correct answer is option 'B'. Can you explain this answer?
On Mollier chart, flow through turbine is represented by
a)
horizontal straight line
b)
straight inclined line
c)
vertical straight line
d)
curved line
e)
none of the above
|
Arshiya Dasgupta answered |
Mollier chart representation of flow through turbine
Introduction:
Mollier chart is a graphical representation of thermodynamic properties of a substance. It is also known as enthalpy-entropy chart. It is widely used in the field of power engineering to analyze and design thermodynamic systems.
Flow through turbine:
Turbine is a device which converts the energy of fluid flow into mechanical work. The flow of fluid through the turbine is determined by the thermodynamic properties of the fluid. The Mollier chart is used to represent the flow of fluid through the turbine.
Representation of flow through turbine on Mollier chart:
The flow of fluid through the turbine is represented by a straight inclined line on the Mollier chart. The line starts from the inlet point of the turbine, which is the state of the fluid before entering the turbine. The line ends at the outlet point of the turbine, which is the state of the fluid after passing through the turbine.
Explanation:
The slope of the line represents the change in enthalpy of the fluid due to the work done by the turbine. The vertical distance between the inlet and outlet points represents the change in entropy of the fluid due to the irreversible process of the turbine. The shape of the line depends on the type of turbine and the properties of the fluid.
Conclusion:
In conclusion, the flow of fluid through the turbine is represented by a straight inclined line on the Mollier chart. The line represents the change in enthalpy and entropy of the fluid due to the work done by the turbine. The Mollier chart is a useful tool for analyzing and designing thermodynamic systems.
Introduction:
Mollier chart is a graphical representation of thermodynamic properties of a substance. It is also known as enthalpy-entropy chart. It is widely used in the field of power engineering to analyze and design thermodynamic systems.
Flow through turbine:
Turbine is a device which converts the energy of fluid flow into mechanical work. The flow of fluid through the turbine is determined by the thermodynamic properties of the fluid. The Mollier chart is used to represent the flow of fluid through the turbine.
Representation of flow through turbine on Mollier chart:
The flow of fluid through the turbine is represented by a straight inclined line on the Mollier chart. The line starts from the inlet point of the turbine, which is the state of the fluid before entering the turbine. The line ends at the outlet point of the turbine, which is the state of the fluid after passing through the turbine.
Explanation:
The slope of the line represents the change in enthalpy of the fluid due to the work done by the turbine. The vertical distance between the inlet and outlet points represents the change in entropy of the fluid due to the irreversible process of the turbine. The shape of the line depends on the type of turbine and the properties of the fluid.
Conclusion:
In conclusion, the flow of fluid through the turbine is represented by a straight inclined line on the Mollier chart. The line represents the change in enthalpy and entropy of the fluid due to the work done by the turbine. The Mollier chart is a useful tool for analyzing and designing thermodynamic systems.
An ideal regenerative cycle is- a)equal to carnot cycle
- b)less than carnot cycle
- c)more than carnot cycle
- d)could be anything
- e)none of the above
Correct answer is option 'B'. Can you explain this answer?
An ideal regenerative cycle is
a)
equal to carnot cycle
b)
less than carnot cycle
c)
more than carnot cycle
d)
could be anything
e)
none of the above
|
Nitin Joshi answered |
Regenerative Cycle
The regenerative cycle is a thermodynamic cycle that is used in power plants to increase the efficiency of steam turbines. It is a modification of the Rankine cycle, which is the most commonly used cycle in power plants. The regenerative cycle involves the use of a feedwater heater to preheat the water before it enters the boiler. This reduces the amount of heat that is required to produce steam and increases the efficiency of the cycle.
Ideal Regenerative Cycle
An ideal regenerative cycle is a theoretical cycle that is designed to operate with maximum efficiency. It is an improvement over the Rankine cycle, which has limitations due to the irreversibility of the process. The ideal regenerative cycle is designed to be more efficient than the Rankine cycle by using a series of feedwater heaters to preheat the water before it enters the boiler.
Comparison with Carnot Cycle
The Carnot cycle is a theoretical cycle that is designed to be the most efficient cycle possible. It is often used as a benchmark for comparing other cycles. The ideal regenerative cycle is less efficient than the Carnot cycle because it involves heat transfer between two fluids at different temperatures.
Conclusion
In conclusion, an ideal regenerative cycle is less efficient than the Carnot cycle but more efficient than the Rankine cycle. It is a modification of the Rankine cycle that involves the use of feedwater heaters to preheat the water before it enters the boiler. The ideal regenerative cycle is designed to operate with maximum efficiency and is an improvement over the Rankine cycle.
The regenerative cycle is a thermodynamic cycle that is used in power plants to increase the efficiency of steam turbines. It is a modification of the Rankine cycle, which is the most commonly used cycle in power plants. The regenerative cycle involves the use of a feedwater heater to preheat the water before it enters the boiler. This reduces the amount of heat that is required to produce steam and increases the efficiency of the cycle.
Ideal Regenerative Cycle
An ideal regenerative cycle is a theoretical cycle that is designed to operate with maximum efficiency. It is an improvement over the Rankine cycle, which has limitations due to the irreversibility of the process. The ideal regenerative cycle is designed to be more efficient than the Rankine cycle by using a series of feedwater heaters to preheat the water before it enters the boiler.
Comparison with Carnot Cycle
The Carnot cycle is a theoretical cycle that is designed to be the most efficient cycle possible. It is often used as a benchmark for comparing other cycles. The ideal regenerative cycle is less efficient than the Carnot cycle because it involves heat transfer between two fluids at different temperatures.
Conclusion
In conclusion, an ideal regenerative cycle is less efficient than the Carnot cycle but more efficient than the Rankine cycle. It is a modification of the Rankine cycle that involves the use of feedwater heaters to preheat the water before it enters the boiler. The ideal regenerative cycle is designed to operate with maximum efficiency and is an improvement over the Rankine cycle.
Efficiency of ranking cycle can be increased by- a)increasing initial steam pressure and temperature
- b)increasing exhaust pressure
- c)decreasing exhaust pressure
- d)increasing the expansion ratio
- e)increasing number of regenerative heaters
Correct answer is option 'A'. Can you explain this answer?
Efficiency of ranking cycle can be increased by
a)
increasing initial steam pressure and temperature
b)
increasing exhaust pressure
c)
decreasing exhaust pressure
d)
increasing the expansion ratio
e)
increasing number of regenerative heaters
|
Avik Chaudhary answered |
Introduction
The efficiency of a ranking cycle can be significantly improved by optimizing various parameters. One of the most effective methods is through increasing the initial steam pressure and temperature.
Impact of Initial Steam Pressure and Temperature
- Higher Thermal Efficiency: Increasing the initial steam pressure and temperature raises the average temperature at which heat is added to the cycle. This enhances the thermodynamic efficiency by maximizing the work output from the steam.
- Improved Rankine Cycle Performance: A higher initial steam condition leads to a greater temperature differential between the heat source and the heat sink, which in turn increases the overall cycle efficiency.
- Reduced Heat Losses: Elevated steam conditions can minimize heat losses during the heat addition process, allowing for more effective energy conversion into work.
Comparative Analysis with Other Options
- Option B - Increasing Exhaust Pressure: This would actually decrease the efficiency, as a higher exhaust pressure reduces the expansion ratio, limiting the work output.
- Option C - Decreasing Exhaust Pressure: While this can improve efficiency, it is not as effective as increasing the initial steam conditions.
- Option D - Increasing the Expansion Ratio: This can enhance efficiency, but it is often constrained by material limits and operational parameters.
- Option E - Increasing the Number of Regenerative Heaters: While this can improve efficiency, the initial conditions have a more pronounced effect on the overall cycle performance.
Conclusion
In conclusion, increasing the initial steam pressure and temperature is the most direct and impactful method for enhancing the efficiency of the Rankine cycle, making it the optimal choice for performance improvement.
The efficiency of a ranking cycle can be significantly improved by optimizing various parameters. One of the most effective methods is through increasing the initial steam pressure and temperature.
Impact of Initial Steam Pressure and Temperature
- Higher Thermal Efficiency: Increasing the initial steam pressure and temperature raises the average temperature at which heat is added to the cycle. This enhances the thermodynamic efficiency by maximizing the work output from the steam.
- Improved Rankine Cycle Performance: A higher initial steam condition leads to a greater temperature differential between the heat source and the heat sink, which in turn increases the overall cycle efficiency.
- Reduced Heat Losses: Elevated steam conditions can minimize heat losses during the heat addition process, allowing for more effective energy conversion into work.
Comparative Analysis with Other Options
- Option B - Increasing Exhaust Pressure: This would actually decrease the efficiency, as a higher exhaust pressure reduces the expansion ratio, limiting the work output.
- Option C - Decreasing Exhaust Pressure: While this can improve efficiency, it is not as effective as increasing the initial steam conditions.
- Option D - Increasing the Expansion Ratio: This can enhance efficiency, but it is often constrained by material limits and operational parameters.
- Option E - Increasing the Number of Regenerative Heaters: While this can improve efficiency, the initial conditions have a more pronounced effect on the overall cycle performance.
Conclusion
In conclusion, increasing the initial steam pressure and temperature is the most direct and impactful method for enhancing the efficiency of the Rankine cycle, making it the optimal choice for performance improvement.
Adiabatic process is- a)essentially an isentropic process
- b)non-heat transfer process
- c)reversible process
- d)constant temperature process
- e)None of the above
Correct answer is option 'B'. Can you explain this answer?
Adiabatic process is
a)
essentially an isentropic process
b)
non-heat transfer process
c)
reversible process
d)
constant temperature process
e)
None of the above
|
Akshara Rane answered |
Adiabatic process is a non-heat transfer process. In this process, there is no exchange of heat between the system and its surroundings. The term "adiabatic" comes from the Greek words "a" (meaning "without") and "diabatos" (meaning "passing through").
Explanation:
- Adiabatic process is essentially an isentropic process: This statement is incorrect. While it is true that adiabatic process can be isentropic, it is not always the case. Isentropic process refers to a process in which the entropy remains constant, while adiabatic process refers to a process in which there is no heat transfer. An isentropic process can be adiabatic, but an adiabatic process may not be isentropic.
- Adiabatic process is a reversible process: This statement is incorrect. Adiabatic process can be reversible or irreversible. The reversibility of a process depends on various factors such as friction, heat transfer, and the presence of irreversibilities within the system.
- Adiabatic process is a constant temperature process: This statement is incorrect. In an adiabatic process, there is no heat transfer, but it does not necessarily mean that the temperature remains constant. The temperature can change during an adiabatic process due to the work done on or by the system.
- Adiabatic process is a non-heat transfer process: This statement is correct. Adiabatic process refers to a process in which there is no heat transfer between the system and its surroundings. It means that the system is thermally isolated, and any change in the system's energy is solely due to work done on or by the system.
- None of the above: This statement is incorrect. The correct answer is option 'B', which states that adiabatic process is a non-heat transfer process.
To summarize, adiabatic process is a non-heat transfer process in which there is no exchange of heat between the system and its surroundings. It can be reversible or irreversible, isentropic or non-isentropic, and the temperature can change during the process.
Explanation:
- Adiabatic process is essentially an isentropic process: This statement is incorrect. While it is true that adiabatic process can be isentropic, it is not always the case. Isentropic process refers to a process in which the entropy remains constant, while adiabatic process refers to a process in which there is no heat transfer. An isentropic process can be adiabatic, but an adiabatic process may not be isentropic.
- Adiabatic process is a reversible process: This statement is incorrect. Adiabatic process can be reversible or irreversible. The reversibility of a process depends on various factors such as friction, heat transfer, and the presence of irreversibilities within the system.
- Adiabatic process is a constant temperature process: This statement is incorrect. In an adiabatic process, there is no heat transfer, but it does not necessarily mean that the temperature remains constant. The temperature can change during an adiabatic process due to the work done on or by the system.
- Adiabatic process is a non-heat transfer process: This statement is correct. Adiabatic process refers to a process in which there is no heat transfer between the system and its surroundings. It means that the system is thermally isolated, and any change in the system's energy is solely due to work done on or by the system.
- None of the above: This statement is incorrect. The correct answer is option 'B', which states that adiabatic process is a non-heat transfer process.
To summarize, adiabatic process is a non-heat transfer process in which there is no exchange of heat between the system and its surroundings. It can be reversible or irreversible, isentropic or non-isentropic, and the temperature can change during the process.
Induced draught fans of a large steam generator have- a)backward curved blades
- b)forward curved blades
- c)straight of radial blades
- d)double curved blades
Correct answer is option 'A'. Can you explain this answer?
Induced draught fans of a large steam generator have
a)
backward curved blades
b)
forward curved blades
c)
straight of radial blades
d)
double curved blades
|
Shail Rane answered |
Induced Draught Fans for Large Steam Generators:
Induced draught fans are used in large steam generators to draw the flue gases produced during combustion away from the furnace and through the boiler. These fans are critical in maintaining the proper pressure levels, which in turn ensures optimal combustion and heat transfer efficiency. The blades of these fans play a crucial role in determining their performance.
Backward Curved Blades:
The correct answer for this question is option 'A', which is backward curved blades. These types of blades are commonly used in induced draught fans for large steam generators. The following are some of the reasons for their popularity:
- Efficiency: Backward curved blades are highly efficient in terms of converting energy into mechanical work. They can achieve high static pressures with relatively low power consumption.
- Low noise: These blades are designed in such a way that they produce less noise compared to other types of blades. This is important for maintaining a comfortable working environment for the operators.
- High durability: Backward curved blades are more durable than other types of blades. They can withstand high temperatures and corrosive environments, which are common in large steam generators.
Conclusion:
In conclusion, induced draught fans for large steam generators use backward curved blades due to their high efficiency, low noise, and high durability. These blades are critical in ensuring optimal performance of the steam generator, and their selection should be done carefully based on the specific requirements of the application.
Induced draught fans are used in large steam generators to draw the flue gases produced during combustion away from the furnace and through the boiler. These fans are critical in maintaining the proper pressure levels, which in turn ensures optimal combustion and heat transfer efficiency. The blades of these fans play a crucial role in determining their performance.
Backward Curved Blades:
The correct answer for this question is option 'A', which is backward curved blades. These types of blades are commonly used in induced draught fans for large steam generators. The following are some of the reasons for their popularity:
- Efficiency: Backward curved blades are highly efficient in terms of converting energy into mechanical work. They can achieve high static pressures with relatively low power consumption.
- Low noise: These blades are designed in such a way that they produce less noise compared to other types of blades. This is important for maintaining a comfortable working environment for the operators.
- High durability: Backward curved blades are more durable than other types of blades. They can withstand high temperatures and corrosive environments, which are common in large steam generators.
Conclusion:
In conclusion, induced draught fans for large steam generators use backward curved blades due to their high efficiency, low noise, and high durability. These blades are critical in ensuring optimal performance of the steam generator, and their selection should be done carefully based on the specific requirements of the application.
At constant efficiency, the horse power of a fan is- a)Proportional to rpm
- b)Proportional to (rpm)2
- c)Proportional to (rpm)3
- d)A polynomial function of rpm
Correct answer is option 'C'. Can you explain this answer?
At constant efficiency, the horse power of a fan is
a)
Proportional to rpm
b)
Proportional to (rpm)2
c)
Proportional to (rpm)3
d)
A polynomial function of rpm
|
Lavanya Menon answered |
-
At constant efficiency, the horse power of a fan is p
roportional to (rpm)3.-Essentially the electric fans take 1/2 horsepower
Coke is produced by- a)pulverising coal in inert atmosphere
- b)heating wood in a limited supply of air at temperatures below 300ºC
- c)strongly heating coal continuously for about 48 hours in the absence of air in a closed vessel
- d)binding the pulverised coal into bricketts
- e)enriching carbon in the coal.
Correct answer is option 'C'. Can you explain this answer?
Coke is produced by
a)
pulverising coal in inert atmosphere
b)
heating wood in a limited supply of air at temperatures below 300ºC
c)
strongly heating coal continuously for about 48 hours in the absence of air in a closed vessel
d)
binding the pulverised coal into bricketts
e)
enriching carbon in the coal.
|
|
Baishali Bajaj answered |
Coke is a fuel with a high carbon content and few impurities, made by heating coal in the absence of air. It is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulphur bituminous coal. Cokes made from coal are grey, hard, and porous.HENCE, CORRECT OPTION IS (C).
The saturation temperature of steam with increase in pressure increases- a)linearly
- b)rapidly first and then slowly
- c)slowly first and then rapidly
- d)inversely
- e)none of the above
Correct answer is option 'B'. Can you explain this answer?
The saturation temperature of steam with increase in pressure increases
a)
linearly
b)
rapidly first and then slowly
c)
slowly first and then rapidly
d)
inversely
e)
none of the above
|
Debolina Menon answered |
Saturation Temperature and Pressure of Steam
Saturation temperature and pressure are the two thermodynamic properties that are commonly used to define the state of steam. Saturation temperature is the temperature at which steam exists in a saturated state, i.e., a state where water and steam coexist in equilibrium. Saturation pressure is the pressure at which steam exists in a saturated state at a given temperature.
Relationship between Saturation Temperature and Pressure
The relationship between saturation temperature and pressure of steam is called the saturation curve. This curve is a plot of saturation temperature against pressure. The saturation curve is unique for each substance and can be determined experimentally. For water, the saturation curve is commonly referred to as the steam table.
Effect of Pressure on Saturation Temperature
The saturation temperature of steam increases with an increase in pressure. When the pressure is increased, the energy required to maintain the equilibrium between water and steam increases. Thus, the temperature at which this equilibrium is maintained also increases.
The rate at which the saturation temperature increases with pressure depends on the substance. For water, the saturation temperature increases rapidly at low pressures and then increases at a slower rate at high pressures. This can be explained by the fact that at low pressures, the energy required to maintain the equilibrium between water and steam is relatively small. Thus, a small increase in pressure leads to a large increase in saturation temperature. However, at high pressures, the energy required to maintain the equilibrium between water and steam is already high. Thus, a small increase in pressure leads to a smaller increase in saturation temperature.
Conclusion
In conclusion, the saturation temperature of steam increases with an increase in pressure. For water, the saturation temperature increases rapidly at low pressures and then increases at a slower rate at high pressures. This relationship is important in various applications, such as steam power plants and refrigeration systems, where knowledge of the thermodynamic properties of steam is essential.
Saturation temperature and pressure are the two thermodynamic properties that are commonly used to define the state of steam. Saturation temperature is the temperature at which steam exists in a saturated state, i.e., a state where water and steam coexist in equilibrium. Saturation pressure is the pressure at which steam exists in a saturated state at a given temperature.
Relationship between Saturation Temperature and Pressure
The relationship between saturation temperature and pressure of steam is called the saturation curve. This curve is a plot of saturation temperature against pressure. The saturation curve is unique for each substance and can be determined experimentally. For water, the saturation curve is commonly referred to as the steam table.
Effect of Pressure on Saturation Temperature
The saturation temperature of steam increases with an increase in pressure. When the pressure is increased, the energy required to maintain the equilibrium between water and steam increases. Thus, the temperature at which this equilibrium is maintained also increases.
The rate at which the saturation temperature increases with pressure depends on the substance. For water, the saturation temperature increases rapidly at low pressures and then increases at a slower rate at high pressures. This can be explained by the fact that at low pressures, the energy required to maintain the equilibrium between water and steam is relatively small. Thus, a small increase in pressure leads to a large increase in saturation temperature. However, at high pressures, the energy required to maintain the equilibrium between water and steam is already high. Thus, a small increase in pressure leads to a smaller increase in saturation temperature.
Conclusion
In conclusion, the saturation temperature of steam increases with an increase in pressure. For water, the saturation temperature increases rapidly at low pressures and then increases at a slower rate at high pressures. This relationship is important in various applications, such as steam power plants and refrigeration systems, where knowledge of the thermodynamic properties of steam is essential.
Efficiency of a thermal cycle increases by- a)regeneration
- b)reheating of steam
- c)both (a) and (b)
- d)cooling of steam
- e)none of the above
Correct answer is option 'C'. Can you explain this answer?
Efficiency of a thermal cycle increases by
a)
regeneration
b)
reheating of steam
c)
both (a) and (b)
d)
cooling of steam
e)
none of the above
|
Keerthana Joshi answered |
Efficiency of a Thermal Cycle
Thermal cycles are used in various industries to convert heat into mechanical work. The efficiency of a thermal cycle is the ratio of the work output to the heat input. It depends on various factors such as the temperature of the heat source, the temperature of the heat sink, and the type of cycle used.
Regeneration
Regeneration is a process in which the waste heat from the exhaust of a turbine is used to preheat the compressed air before it enters the combustion chamber. This process increases the efficiency of the cycle by reducing the amount of fuel required to produce the same amount of work. The heat exchanger used in the regeneration process is called a regenerator.
Reheating of Steam
Reheating of steam is another process used to increase the efficiency of a thermal cycle. In this process, the steam from the high-pressure turbine is passed through a reheater, where it is heated again before entering the low-pressure turbine. This process increases the amount of work done by the turbine and, hence, the efficiency of the cycle.
Both Regeneration and Reheating
Both regeneration and reheating of steam are used in combination in some cycles to further increase the efficiency. The combination of these two processes reduces the amount of fuel required and, hence, the cost of electricity production.
Cooling of Steam
Cooling of steam is a process that reduces the temperature of the exhaust steam before it enters the condenser. This process increases the efficiency of the cycle by reducing the back pressure on the turbine and, hence, the amount of work done by it.
Conclusion
In conclusion, the efficiency of a thermal cycle can be increased by using various processes such as regeneration, reheating of steam, and cooling of steam. The combination of these processes can further increase the efficiency of the cycle and reduce the cost of electricity production.
Thermal cycles are used in various industries to convert heat into mechanical work. The efficiency of a thermal cycle is the ratio of the work output to the heat input. It depends on various factors such as the temperature of the heat source, the temperature of the heat sink, and the type of cycle used.
Regeneration
Regeneration is a process in which the waste heat from the exhaust of a turbine is used to preheat the compressed air before it enters the combustion chamber. This process increases the efficiency of the cycle by reducing the amount of fuel required to produce the same amount of work. The heat exchanger used in the regeneration process is called a regenerator.
Reheating of Steam
Reheating of steam is another process used to increase the efficiency of a thermal cycle. In this process, the steam from the high-pressure turbine is passed through a reheater, where it is heated again before entering the low-pressure turbine. This process increases the amount of work done by the turbine and, hence, the efficiency of the cycle.
Both Regeneration and Reheating
Both regeneration and reheating of steam are used in combination in some cycles to further increase the efficiency. The combination of these two processes reduces the amount of fuel required and, hence, the cost of electricity production.
Cooling of Steam
Cooling of steam is a process that reduces the temperature of the exhaust steam before it enters the condenser. This process increases the efficiency of the cycle by reducing the back pressure on the turbine and, hence, the amount of work done by it.
Conclusion
In conclusion, the efficiency of a thermal cycle can be increased by using various processes such as regeneration, reheating of steam, and cooling of steam. The combination of these processes can further increase the efficiency of the cycle and reduce the cost of electricity production.
One kg of steam sample contains 0.8 kg dry steam; it's dryness fraction is- a)0.2
- b)0.8
- c)1.0
- d)0.6
- e)0.5
Correct answer is option 'B'. Can you explain this answer?
One kg of steam sample contains 0.8 kg dry steam; it's dryness fraction is
a)
0.2
b)
0.8
c)
1.0
d)
0.6
e)
0.5
|
Ayush Chawla answered |
Given:
- Mass of steam sample = 1 kg
- Mass of dry steam = 0.8 kg
To find:
- Dryness fraction of steam
Solution:
Dryness fraction is defined as the ratio of mass of dry steam to the total mass of steam. Mathematically,
Dryness fraction = (Mass of dry steam) / (Mass of steam sample)
Substituting the given values,
Dryness fraction = 0.8 kg / 1 kg = 0.8
Therefore, the dryness fraction of the steam sample is 0.8, which means that 80% of the steam sample is in the form of dry steam.
Answer:
The correct option is (B) 0.8.
- Mass of steam sample = 1 kg
- Mass of dry steam = 0.8 kg
To find:
- Dryness fraction of steam
Solution:
Dryness fraction is defined as the ratio of mass of dry steam to the total mass of steam. Mathematically,
Dryness fraction = (Mass of dry steam) / (Mass of steam sample)
Substituting the given values,
Dryness fraction = 0.8 kg / 1 kg = 0.8
Therefore, the dryness fraction of the steam sample is 0.8, which means that 80% of the steam sample is in the form of dry steam.
Answer:
The correct option is (B) 0.8.
In forced circulation boilers, about 90% of water is recirculated without evaporation. The circulation ratio is- a)0.1
- b)0.9
- c)9
- d)10
Correct answer is option 'D'. Can you explain this answer?
In forced circulation boilers, about 90% of water is recirculated without evaporation. The circulation ratio is
a)
0.1
b)
0.9
c)
9
d)
10
|
Zoya Sharma answered |
-
A forced circulation boiler is a boiler where a pump is used to circulate water inside the boiler. This differs from a natural circulation boiler which relies on current density to circulate water inside the boiler. In some forced circulation boilers, the water is circulated twenty times the rate of evaporation.
-In forced circulation boilers, about 90% of water is recirculated without evaporation. The circulation ratio is 10.
For water, at pressures below atmospheric,- a)melting point rises slightly and boiling point drops markedly
- b)melting point rises markedly and boiling point drops markedly
- c)melting point drops slightly and boiling point drops markedly
- d)melting point drops slightly and boiling point drops slightly
- e)none of the above
Correct answer is option 'A'. Can you explain this answer?
For water, at pressures below atmospheric,
a)
melting point rises slightly and boiling point drops markedly
b)
melting point rises markedly and boiling point drops markedly
c)
melting point drops slightly and boiling point drops markedly
d)
melting point drops slightly and boiling point drops slightly
e)
none of the above
|
Sagarika Dey answered |
Effects of pressure on water
When the pressure exerted on water is reduced, it affects the properties of water. The effects of pressure on water are:
Melting point
- The melting point of water is the temperature at which water changes from a solid state to a liquid state.
- When the pressure is reduced, the melting point of water rises slightly.
- This happens because the molecules of water are more free to move around, and it takes more energy to bind them together in a solid state.
Boiling point
- The boiling point of water is the temperature at which water changes from a liquid state to a gaseous state.
- When the pressure is reduced, the boiling point of water drops markedly.
- This happens because the molecules of water have less pressure holding them together in a liquid state, and it takes less energy to make them move apart into a gaseous state.
Conclusion
The correct option is A, as when the pressure is reduced, the melting point of water rises slightly and the boiling point of water drops markedly.
When the pressure exerted on water is reduced, it affects the properties of water. The effects of pressure on water are:
Melting point
- The melting point of water is the temperature at which water changes from a solid state to a liquid state.
- When the pressure is reduced, the melting point of water rises slightly.
- This happens because the molecules of water are more free to move around, and it takes more energy to bind them together in a solid state.
Boiling point
- The boiling point of water is the temperature at which water changes from a liquid state to a gaseous state.
- When the pressure is reduced, the boiling point of water drops markedly.
- This happens because the molecules of water have less pressure holding them together in a liquid state, and it takes less energy to make them move apart into a gaseous state.
Conclusion
The correct option is A, as when the pressure is reduced, the melting point of water rises slightly and the boiling point of water drops markedly.
The specific heat of superheated steam in kcal/ kg is generally of the order of- a)0.1
- b)0.3
- c)0.5
- d)0.8
- e)1.0
Correct answer is option 'C'. Can you explain this answer?
The specific heat of superheated steam in kcal/ kg is generally of the order of
a)
0.1
b)
0.3
c)
0.5
d)
0.8
e)
1.0
|
Hiral Jain answered |
Explanation:
Specific heat is defined as the amount of heat required to raise the temperature of unit mass of substance by one degree.
Superheated steam is steam at a temperature higher than its boiling point at the absolute pressure where the temperature is measured.
The specific heat of superheated steam depends on the temperature and pressure of the steam.
At atmospheric pressure, the specific heat of superheated steam is approximately 0.5 kcal/kg.
At higher pressures, the specific heat of superheated steam decreases.
Therefore, the specific heat of superheated steam in kcal/kg is generally of the order of 0.5 kcal/kg.
Specific heat is defined as the amount of heat required to raise the temperature of unit mass of substance by one degree.
Superheated steam is steam at a temperature higher than its boiling point at the absolute pressure where the temperature is measured.
The specific heat of superheated steam depends on the temperature and pressure of the steam.
At atmospheric pressure, the specific heat of superheated steam is approximately 0.5 kcal/kg.
At higher pressures, the specific heat of superheated steam decreases.
Therefore, the specific heat of superheated steam in kcal/kg is generally of the order of 0.5 kcal/kg.
One kilowatt-hour energy is equivalent to- a)1000 J
- b)360 kJ
- c)3600 kJ
- d)3600 kW/sec
- e)1000 kJ
Correct answer is option 'C'. Can you explain this answer?
One kilowatt-hour energy is equivalent to
a)
1000 J
b)
360 kJ
c)
3600 kJ
d)
3600 kW/sec
e)
1000 kJ
|
Bhanu Pratap answered |
1 kwh = 3600,000 J...thats correct
Hygrometry deals with the- a)Hygroscopic substances
- b)water vapour in air
- c)temperature of air
- d)pressure of air
- e)density measurement
Correct answer is option 'B'. Can you explain this answer?
Hygrometry deals with the
a)
Hygroscopic substances
b)
water vapour in air
c)
temperature of air
d)
pressure of air
e)
density measurement
|
|
Bhargavi Chauhan answered |
Hygrometry is the branch of science that deals with the measurement and study of water vapor in the air. It is an important aspect of meteorology and plays a crucial role in various industries such as agriculture, HVAC systems, and manufacturing processes.
Water vapor in the air can greatly affect the comfort, health, and productivity of individuals, as well as the performance and efficiency of various processes and equipment. The measurement and control of humidity levels are essential in many applications to ensure optimal conditions.
Here is a detailed explanation of why option B, "water vapor in air," is the correct answer for the question:
1. Definition of Hygrometry:
- Hygrometry is the scientific study and measurement of humidity, which refers to the amount of water vapor present in the air.
- It involves the measurement and analysis of various parameters related to humidity, including absolute humidity, relative humidity, dew point, and specific humidity.
2. Importance of Water Vapor in Air:
- Water vapor is an important component of the Earth's atmosphere and has a significant impact on weather patterns, cloud formation, and precipitation.
- It affects human comfort and health, as high humidity levels can cause discomfort, while low humidity can lead to dry skin, respiratory problems, and static electricity.
- In industries, humidity control is crucial for processes such as manufacturing, storage, and preservation of products. For example, in the textile industry, humidity levels need to be controlled to prevent the loss of moisture or shrinkage of fabrics.
3. Measurement of Water Vapor:
- Hygrometers are devices used to measure humidity levels. They work on different principles, including the use of hair or synthetic materials that change their length or electrical properties in response to humidity changes.
- Hygrometers provide readings in various units, such as percentage relative humidity (%RH) or grams of water vapor per cubic meter of air (g/m³).
4. Applications of Hygrometry:
- Meteorology: Hygrometry is essential in weather forecasting and climate studies. It helps in understanding atmospheric moisture patterns, cloud formation, and predicting precipitation.
- Agriculture: Humidity control is crucial in greenhouses to create optimal growing conditions for plants. It helps in preventing diseases, controlling transpiration, and maximizing crop production.
- HVAC Systems: Humidity control is important for maintaining comfort and indoor air quality in buildings. It helps in preventing mold growth, reducing static electricity, and optimizing energy efficiency.
- Pharmaceuticals and Electronics: In these industries, precise humidity control is crucial for product stability and preventing moisture-related damage.
In conclusion, hygrometry is the branch of science that deals with the measurement and study of water vapor in the air. It plays a crucial role in various industries and applications where humidity control is essential for optimal conditions, human comfort, and the performance of processes and equipment.
Water vapor in the air can greatly affect the comfort, health, and productivity of individuals, as well as the performance and efficiency of various processes and equipment. The measurement and control of humidity levels are essential in many applications to ensure optimal conditions.
Here is a detailed explanation of why option B, "water vapor in air," is the correct answer for the question:
1. Definition of Hygrometry:
- Hygrometry is the scientific study and measurement of humidity, which refers to the amount of water vapor present in the air.
- It involves the measurement and analysis of various parameters related to humidity, including absolute humidity, relative humidity, dew point, and specific humidity.
2. Importance of Water Vapor in Air:
- Water vapor is an important component of the Earth's atmosphere and has a significant impact on weather patterns, cloud formation, and precipitation.
- It affects human comfort and health, as high humidity levels can cause discomfort, while low humidity can lead to dry skin, respiratory problems, and static electricity.
- In industries, humidity control is crucial for processes such as manufacturing, storage, and preservation of products. For example, in the textile industry, humidity levels need to be controlled to prevent the loss of moisture or shrinkage of fabrics.
3. Measurement of Water Vapor:
- Hygrometers are devices used to measure humidity levels. They work on different principles, including the use of hair or synthetic materials that change their length or electrical properties in response to humidity changes.
- Hygrometers provide readings in various units, such as percentage relative humidity (%RH) or grams of water vapor per cubic meter of air (g/m³).
4. Applications of Hygrometry:
- Meteorology: Hygrometry is essential in weather forecasting and climate studies. It helps in understanding atmospheric moisture patterns, cloud formation, and predicting precipitation.
- Agriculture: Humidity control is crucial in greenhouses to create optimal growing conditions for plants. It helps in preventing diseases, controlling transpiration, and maximizing crop production.
- HVAC Systems: Humidity control is important for maintaining comfort and indoor air quality in buildings. It helps in preventing mold growth, reducing static electricity, and optimizing energy efficiency.
- Pharmaceuticals and Electronics: In these industries, precise humidity control is crucial for product stability and preventing moisture-related damage.
In conclusion, hygrometry is the branch of science that deals with the measurement and study of water vapor in the air. It plays a crucial role in various industries and applications where humidity control is essential for optimal conditions, human comfort, and the performance of processes and equipment.
The bituminous coal is non-caking if its carbon content is- a)78 – 81%
- b)81 – 85%
- c)85 – 90%
- d)90 – 95%
- e)95 – 100%
Correct answer is option 'A'. Can you explain this answer?
The bituminous coal is non-caking if its carbon content is
a)
78 – 81%
b)
81 – 85%
c)
85 – 90%
d)
90 – 95%
e)
95 – 100%
|
Pritam Das answered |
Bituminous coal is one of the most commonly used types of coal in the world due to its high energy content and relatively low cost. However, not all bituminous coal is the same. Some bituminous coals have a high degree of caking, while others are non-caking. In this question, we are asked to determine the carbon content of non-caking bituminous coal.
Explanation:
Caking vs. Non-Caking Bituminous Coal:
Caking coal is a type of bituminous coal that has a high degree of plasticity, which means it can be molded or shaped when it is heated. This property is due to the presence of certain chemical compounds in the coal, such as hydrocarbons and oxygen-containing functional groups. When caking coal is heated, these compounds break down and release gases that cause the coal to soften and become sticky or "plastic." This property is useful in the production of coke, which is a fuel used in steelmaking.
Non-caking coal, on the other hand, does not have this plasticity and does not soften or become sticky when heated. This type of coal is often used as a fuel for power generation and other industrial applications.
Carbon Content of Non-Caking Bituminous Coal:
The carbon content of coal is an important factor in determining its properties and suitability for various uses. Generally, the higher the carbon content, the higher the energy content of the coal. Non-caking bituminous coal typically has a carbon content of around 78-81%, which is lower than the carbon content of anthracite coal (which can have a carbon content of up to 95%).
Conclusion:
In conclusion, the correct answer to this question is option 'A' (78-81%). This range of carbon content is typical for non-caking bituminous coal, which does not have the plasticity and caking properties of other types of bituminous coal. Understanding the properties and characteristics of different types of coal is important for selecting the right fuel for a particular application.
Explanation:
Caking vs. Non-Caking Bituminous Coal:
Caking coal is a type of bituminous coal that has a high degree of plasticity, which means it can be molded or shaped when it is heated. This property is due to the presence of certain chemical compounds in the coal, such as hydrocarbons and oxygen-containing functional groups. When caking coal is heated, these compounds break down and release gases that cause the coal to soften and become sticky or "plastic." This property is useful in the production of coke, which is a fuel used in steelmaking.
Non-caking coal, on the other hand, does not have this plasticity and does not soften or become sticky when heated. This type of coal is often used as a fuel for power generation and other industrial applications.
Carbon Content of Non-Caking Bituminous Coal:
The carbon content of coal is an important factor in determining its properties and suitability for various uses. Generally, the higher the carbon content, the higher the energy content of the coal. Non-caking bituminous coal typically has a carbon content of around 78-81%, which is lower than the carbon content of anthracite coal (which can have a carbon content of up to 95%).
Conclusion:
In conclusion, the correct answer to this question is option 'A' (78-81%). This range of carbon content is typical for non-caking bituminous coal, which does not have the plasticity and caking properties of other types of bituminous coal. Understanding the properties and characteristics of different types of coal is important for selecting the right fuel for a particular application.
Which one of the following accessories is connected to the steam supply pipe line to maintain constant pressure?- a)Pressure reducing valve
- b)Steam separator
- c)Steam trap
- d)Injector
Correct answer is option 'C'. Can you explain this answer?
Which one of the following accessories is connected to the steam supply pipe line to maintain constant pressure?
a)
Pressure reducing valve
b)
Steam separator
c)
Steam trap
d)
Injector
|
|
Ishaan Malik answered |
The correct answer is option 'C', which is a steam trap.
Explanation:
A steam trap is a device that is connected to the steam supply pipe line to maintain constant pressure. It is a type of automatic valve that is used to discharge condensate and non-condensable gases from the steam system without allowing the steam to escape.
Steam traps are important in steam systems as they help to remove condensate, which is the liquid formed when steam cools down and loses its latent heat. If condensate is allowed to accumulate in the steam system, it can cause various issues such as water hammer, reduced heat transfer efficiency, and corrosion. Therefore, it is necessary to remove condensate from the steam system to maintain its performance and efficiency.
Steam traps work by automatically opening to allow condensate and non-condensable gases to be discharged from the system, and then closing to prevent the escape of steam. They are designed to operate at a specific pressure range and are selected based on the specific requirements of the steam system.
There are different types of steam traps available, including float traps, thermostatic traps, and thermodynamic traps. Each type has its own mechanism for discharging condensate and is suitable for different applications.
In summary, a steam trap is connected to the steam supply pipe line to maintain constant pressure by removing condensate and non-condensable gases from the system without allowing the escape of steam. It is an important accessory in steam systems to ensure efficient and reliable operation.
Explanation:
A steam trap is a device that is connected to the steam supply pipe line to maintain constant pressure. It is a type of automatic valve that is used to discharge condensate and non-condensable gases from the steam system without allowing the steam to escape.
Steam traps are important in steam systems as they help to remove condensate, which is the liquid formed when steam cools down and loses its latent heat. If condensate is allowed to accumulate in the steam system, it can cause various issues such as water hammer, reduced heat transfer efficiency, and corrosion. Therefore, it is necessary to remove condensate from the steam system to maintain its performance and efficiency.
Steam traps work by automatically opening to allow condensate and non-condensable gases to be discharged from the system, and then closing to prevent the escape of steam. They are designed to operate at a specific pressure range and are selected based on the specific requirements of the steam system.
There are different types of steam traps available, including float traps, thermostatic traps, and thermodynamic traps. Each type has its own mechanism for discharging condensate and is suitable for different applications.
In summary, a steam trap is connected to the steam supply pipe line to maintain constant pressure by removing condensate and non-condensable gases from the system without allowing the escape of steam. It is an important accessory in steam systems to ensure efficient and reliable operation.
In a surface condenser used in a steam power station, undercooling of condensate is undesirable as this would- a)not absorb the gases in steam
- b)reduce efficiency of the plant
- c)increase the cooling water requirements
- d)increase thermal stresses in the condenser
Correct answer is option 'B'. Can you explain this answer?
In a surface condenser used in a steam power station, undercooling of condensate is undesirable as this would
a)
not absorb the gases in steam
b)
reduce efficiency of the plant
c)
increase the cooling water requirements
d)
increase thermal stresses in the condenser
|
|
Nilesh Verma answered |
Introduction:
In a steam power station, a surface condenser is used to convert the exhaust steam from the turbine back into liquid form, which can be reused in the boiler. The condensate is typically cooled using a cooling water system, which removes heat from the condenser. The undercooling of condensate refers to cooling it below its saturation temperature, which is the temperature at which it would normally condense at a given pressure.
Explanation:
The undercooling of condensate in a surface condenser is undesirable because it reduces the efficiency of the power plant. This can be understood by considering the following points:
1. Effect on heat transfer: Undercooling the condensate reduces the temperature difference between the condensing steam and the cooling water. This decreases the overall heat transfer rate in the condenser. As a result, more cooling water is required to achieve the desired condensation of the steam. This increases the cooling water requirements and the associated pumping power, which leads to a decrease in the overall efficiency of the plant.
2. Effect on turbine efficiency: Undercooling of condensate increases the backpressure on the turbine. The backpressure is the pressure in the exhaust steam path after it passes through the condenser. The increase in backpressure reduces the pressure difference across the turbine, which in turn decreases the turbine efficiency. This results in a lower power output from the turbine and a decrease in the overall efficiency of the plant.
3. Effect on thermal stresses: Undercooling of condensate can also lead to increased thermal stresses in the condenser. When the condensate is cooled below its saturation temperature, it can cause thermal contraction and differential expansion between the condenser tubes and the tube sheets. This can result in increased thermal stresses, which can lead to tube failures and damage to the condenser. Repairing and maintaining the condenser due to such failures can be costly and time-consuming.
Conclusion:
In conclusion, undercooling of condensate in a surface condenser used in a steam power station is undesirable because it reduces the efficiency of the plant, increases the cooling water requirements, and can lead to increased thermal stresses in the condenser. Therefore, it is important to design and operate the condenser in such a way that the condensate is cooled to its saturation temperature, ensuring optimal performance and efficiency of the power plant.
In a steam power station, a surface condenser is used to convert the exhaust steam from the turbine back into liquid form, which can be reused in the boiler. The condensate is typically cooled using a cooling water system, which removes heat from the condenser. The undercooling of condensate refers to cooling it below its saturation temperature, which is the temperature at which it would normally condense at a given pressure.
Explanation:
The undercooling of condensate in a surface condenser is undesirable because it reduces the efficiency of the power plant. This can be understood by considering the following points:
1. Effect on heat transfer: Undercooling the condensate reduces the temperature difference between the condensing steam and the cooling water. This decreases the overall heat transfer rate in the condenser. As a result, more cooling water is required to achieve the desired condensation of the steam. This increases the cooling water requirements and the associated pumping power, which leads to a decrease in the overall efficiency of the plant.
2. Effect on turbine efficiency: Undercooling of condensate increases the backpressure on the turbine. The backpressure is the pressure in the exhaust steam path after it passes through the condenser. The increase in backpressure reduces the pressure difference across the turbine, which in turn decreases the turbine efficiency. This results in a lower power output from the turbine and a decrease in the overall efficiency of the plant.
3. Effect on thermal stresses: Undercooling of condensate can also lead to increased thermal stresses in the condenser. When the condensate is cooled below its saturation temperature, it can cause thermal contraction and differential expansion between the condenser tubes and the tube sheets. This can result in increased thermal stresses, which can lead to tube failures and damage to the condenser. Repairing and maintaining the condenser due to such failures can be costly and time-consuming.
Conclusion:
In conclusion, undercooling of condensate in a surface condenser used in a steam power station is undesirable because it reduces the efficiency of the plant, increases the cooling water requirements, and can lead to increased thermal stresses in the condenser. Therefore, it is important to design and operate the condenser in such a way that the condensate is cooled to its saturation temperature, ensuring optimal performance and efficiency of the power plant.
The following boiler makes use of pressurized combustion- a)Velox
- b)Benson
- c)Loeffler
- d)Lamont
- e)forced circulating boiler
Correct answer is option 'A'. Can you explain this answer?
The following boiler makes use of pressurized combustion
a)
Velox
b)
Benson
c)
Loeffler
d)
Lamont
e)
forced circulating boiler
|
|
Gopal Choudhury answered |
Pressurized Combustion in Velox Boiler
Velox boiler is a forced circulation water tube boiler in which the combustion takes place under pressure. This type of boiler makes use of pressurized combustion to achieve high thermal efficiency. Let's understand the working of Velox boiler in detail.
Working Principle of Velox Boiler
The working principle of Velox boiler is based on the forced circulation of water through the tubes. The combustion takes place in a combustion chamber which is located at the bottom of the boiler. The fuel is burnt under pressure and the hot gases are directed to the combustion chamber. The combustion gases pass through a series of air ducts and then enter the combustion chamber.
After entering the combustion chamber, the hot gases mix with the compressed air. The compressed air is supplied by a compressor which is driven by a turbine. The compressed air mixes with the hot gases and the mixture is directed to the heating surface of the boiler.
The heating surface of the boiler consists of a set of tubes through which water circulates. The hot gases transfer their heat to the water and the water gets converted into steam. The steam is then directed to the superheater where it gets superheated. The superheated steam is then sent to the turbine for generating power.
Advantages of Velox Boiler
- High thermal efficiency
- Compact design
- Easy to operate
- Low maintenance cost
Conclusion
Velox boiler is a type of water tube boiler which makes use of pressurized combustion to achieve high thermal efficiency. The boiler operates on the principle of forced circulation and is suitable for power generation applications. The boiler is easy to operate and has a low maintenance cost.
Velox boiler is a forced circulation water tube boiler in which the combustion takes place under pressure. This type of boiler makes use of pressurized combustion to achieve high thermal efficiency. Let's understand the working of Velox boiler in detail.
Working Principle of Velox Boiler
The working principle of Velox boiler is based on the forced circulation of water through the tubes. The combustion takes place in a combustion chamber which is located at the bottom of the boiler. The fuel is burnt under pressure and the hot gases are directed to the combustion chamber. The combustion gases pass through a series of air ducts and then enter the combustion chamber.
After entering the combustion chamber, the hot gases mix with the compressed air. The compressed air is supplied by a compressor which is driven by a turbine. The compressed air mixes with the hot gases and the mixture is directed to the heating surface of the boiler.
The heating surface of the boiler consists of a set of tubes through which water circulates. The hot gases transfer their heat to the water and the water gets converted into steam. The steam is then directed to the superheater where it gets superheated. The superheated steam is then sent to the turbine for generating power.
Advantages of Velox Boiler
- High thermal efficiency
- Compact design
- Easy to operate
- Low maintenance cost
Conclusion
Velox boiler is a type of water tube boiler which makes use of pressurized combustion to achieve high thermal efficiency. The boiler operates on the principle of forced circulation and is suitable for power generation applications. The boiler is easy to operate and has a low maintenance cost.
Once- through boilers operate at- a)subcritical pressure
- b)supercritical pressure
- c)subcritical as well supercritical pressures
- d)critical pressure only
Correct answer is option 'C'. Can you explain this answer?
Once- through boilers operate at
a)
subcritical pressure
b)
supercritical pressure
c)
subcritical as well supercritical pressures
d)
critical pressure only
|
|
Nisha Singh answered |
Explanation:
Once-through Boilers:
Once-through boilers operate at both subcritical and supercritical pressures. These boilers do not have a steam drum like traditional boilers, and water is heated as it flows through the tubes.
Subcritical Pressure:
- At subcritical pressures, water enters the boiler and is heated to its boiling point, producing steam.
- The water-steam mixture then flows through the tubes and is separated into water and steam in the steam drum.
Supercritical Pressure:
- At supercritical pressures, water is heated above its critical point, where there is no distinction between liquid and gas phase.
- The water-steam mixture flows through the tubes without the need for a steam drum, as there is no phase change occurring.
Advantages of Operating at Both Pressures:
- Operating at subcritical pressure allows for better control over the steam generation process.
- Operating at supercritical pressure increases efficiency by eliminating the need for a steam drum and reducing energy losses.
Conclusion:
Once-through boilers are capable of operating at both subcritical and supercritical pressures, providing flexibility and efficiency in steam generation processes.
Once-through Boilers:
Once-through boilers operate at both subcritical and supercritical pressures. These boilers do not have a steam drum like traditional boilers, and water is heated as it flows through the tubes.
Subcritical Pressure:
- At subcritical pressures, water enters the boiler and is heated to its boiling point, producing steam.
- The water-steam mixture then flows through the tubes and is separated into water and steam in the steam drum.
Supercritical Pressure:
- At supercritical pressures, water is heated above its critical point, where there is no distinction between liquid and gas phase.
- The water-steam mixture flows through the tubes without the need for a steam drum, as there is no phase change occurring.
Advantages of Operating at Both Pressures:
- Operating at subcritical pressure allows for better control over the steam generation process.
- Operating at supercritical pressure increases efficiency by eliminating the need for a steam drum and reducing energy losses.
Conclusion:
Once-through boilers are capable of operating at both subcritical and supercritical pressures, providing flexibility and efficiency in steam generation processes.
A device which is used to drain off water from steam pipes without escape of steam is called- a)Steam separator
- b)Steam trap
- c)Pressure reducing valve
- d)Injector
Correct answer is option 'B'. Can you explain this answer?
A device which is used to drain off water from steam pipes without escape of steam is called
a)
Steam separator
b)
Steam trap
c)
Pressure reducing valve
d)
Injector
|
Nishanth Basu answered |
Steam Trap - Explanation
Introduction:
A steam trap is a mechanical device that is used to drain off water from steam pipes without any escape of steam. It is an essential component of a steam system, which helps in maintaining the proper functioning of the system.
Working of a Steam Trap:
The working of a steam trap is based on the principle of the difference in the specific gravity of steam and water. The steam trap is designed in such a way that it can detect the difference between the two and can discharge the water from the steam system, while retaining the steam within the system.
Types of Steam Traps:
There are various types of steam traps available in the market, but the most commonly used steam traps are as follows:
• Mechanical Traps
• Thermodynamic Traps
• Thermostatic Traps
Advantages of using a Steam Trap:
Some of the advantages of using a steam trap are as follows:
• It helps in removing the unwanted condensate from the steam system.
• It helps in maintaining the efficiency of the steam system.
• It helps in reducing the energy consumption of the steam system.
• It helps in preventing the damage to the steam system due to the accumulation of condensate.
Conclusion:
In conclusion, a steam trap is a crucial component of a steam system, which helps in maintaining the proper functioning of the system. It is essential to choose the right type of steam trap, depending on the requirements of the system.
Introduction:
A steam trap is a mechanical device that is used to drain off water from steam pipes without any escape of steam. It is an essential component of a steam system, which helps in maintaining the proper functioning of the system.
Working of a Steam Trap:
The working of a steam trap is based on the principle of the difference in the specific gravity of steam and water. The steam trap is designed in such a way that it can detect the difference between the two and can discharge the water from the steam system, while retaining the steam within the system.
Types of Steam Traps:
There are various types of steam traps available in the market, but the most commonly used steam traps are as follows:
• Mechanical Traps
• Thermodynamic Traps
• Thermostatic Traps
Advantages of using a Steam Trap:
Some of the advantages of using a steam trap are as follows:
• It helps in removing the unwanted condensate from the steam system.
• It helps in maintaining the efficiency of the steam system.
• It helps in reducing the energy consumption of the steam system.
• It helps in preventing the damage to the steam system due to the accumulation of condensate.
Conclusion:
In conclusion, a steam trap is a crucial component of a steam system, which helps in maintaining the proper functioning of the system. It is essential to choose the right type of steam trap, depending on the requirements of the system.
Lancashire boiler is a- a)stationary fire tube boiler
- b)stationary water tube boiler
- c)water tube boiler with natural/forced circulation
- d)mobile fire tube boiler
- e)none of the above
Correct answer is option 'A'. Can you explain this answer?
Lancashire boiler is a
a)
stationary fire tube boiler
b)
stationary water tube boiler
c)
water tube boiler with natural/forced circulation
d)
mobile fire tube boiler
e)
none of the above
|
|
Sanskriti Chakraborty answered |
Lancashire Boiler: A Stationary Fire Tube Boiler
Introduction:
Lancashire boiler is a type of stationary fire tube boiler. It was invented in the year 1844 by the British engineer William Fairbairn. This type of boiler is named after the county of Lancashire, England, where it was first introduced.
Construction:
The Lancashire boiler consists of a horizontal cylindrical shell with two large flue tubes that pass through the furnace. The furnace is located at the front end of the boiler and is surrounded by water. The combustion gases pass through the flue tubes and exit into the atmosphere through the chimney. The boiler has two fire tubes that run horizontally through the length of the boiler. These fire tubes are surrounded by water and connect the front end and back end of the boiler.
Working:
The fuel is burnt in the furnace and the hot gases produced rise upward and pass through the flue tubes. The heat from these gases is transferred to the water surrounding the fire tubes. The water gets heated up and starts rising upward due to convection. The hot water from the top of the boiler is taken out through a steam dome and then distributed to the different parts of the plant.
Advantages:
1. It is a simple and reliable design.
2. It has a large heating surface area which results in high steam production rate.
3. It is capable of handling large volumes of water and steam.
4. It requires less maintenance compared to other types of boilers.
Disadvantages:
1. It has a slow response to load changes.
2. It requires a large amount of floor space.
3. It is not suitable for high-pressure steam applications.
Conclusion:
The Lancashire boiler is a stationary fire tube boiler that has been used in various industries for more than a century. Despite its disadvantages, it is still popular in some industries due to its simplicity and reliability.
Introduction:
Lancashire boiler is a type of stationary fire tube boiler. It was invented in the year 1844 by the British engineer William Fairbairn. This type of boiler is named after the county of Lancashire, England, where it was first introduced.
Construction:
The Lancashire boiler consists of a horizontal cylindrical shell with two large flue tubes that pass through the furnace. The furnace is located at the front end of the boiler and is surrounded by water. The combustion gases pass through the flue tubes and exit into the atmosphere through the chimney. The boiler has two fire tubes that run horizontally through the length of the boiler. These fire tubes are surrounded by water and connect the front end and back end of the boiler.
Working:
The fuel is burnt in the furnace and the hot gases produced rise upward and pass through the flue tubes. The heat from these gases is transferred to the water surrounding the fire tubes. The water gets heated up and starts rising upward due to convection. The hot water from the top of the boiler is taken out through a steam dome and then distributed to the different parts of the plant.
Advantages:
1. It is a simple and reliable design.
2. It has a large heating surface area which results in high steam production rate.
3. It is capable of handling large volumes of water and steam.
4. It requires less maintenance compared to other types of boilers.
Disadvantages:
1. It has a slow response to load changes.
2. It requires a large amount of floor space.
3. It is not suitable for high-pressure steam applications.
Conclusion:
The Lancashire boiler is a stationary fire tube boiler that has been used in various industries for more than a century. Despite its disadvantages, it is still popular in some industries due to its simplicity and reliability.
Stoichiometric quantity of air is the- a)air present in atmosphere at NTP conditions
- b)air required for complete combustion of fuel with no excess air
- c)air required for optimum combustion so as to have reasonable excess air
- d)air required to convert CO into CO2
- e)air required to form an explosive mixture
Correct answer is option 'B'. Can you explain this answer?
Stoichiometric quantity of air is the
a)
air present in atmosphere at NTP conditions
b)
air required for complete combustion of fuel with no excess air
c)
air required for optimum combustion so as to have reasonable excess air
d)
air required to convert CO into CO2
e)
air required to form an explosive mixture
|
|
Sparsh Chakraborty answered |
**Stoichiometric Quantity of Air**
The stoichiometric quantity of air refers to the amount of air required for complete combustion of a fuel with no excess air. It is the theoretical amount of air needed to completely react with all the fuel molecules present, resulting in the complete conversion of fuel to carbon dioxide and water.
**Explanation**
**a) Air present in the atmosphere at NTP conditions**
This option is incorrect because the air present in the atmosphere at normal temperature and pressure (NTP) conditions is not the stoichiometric quantity of air. The air in the atmosphere consists of various gases such as nitrogen, oxygen, carbon dioxide, and traces of other gases, but it does not have a specific stoichiometric ratio.
**b) Air required for complete combustion of fuel with no excess air**
This option is the correct answer. The stoichiometric quantity of air is the exact amount of air required to completely burn a fuel without any excess air. It is based on the chemical reaction between the fuel and oxygen in the air, following the stoichiometric ratio of the reaction equation. This ensures that all the fuel is converted into carbon dioxide and water without any unburned fuel or incomplete combustion products.
**c) Air required for optimum combustion so as to have reasonable excess air**
This option is incorrect because it refers to the air required for optimum combustion, which includes a reasonable amount of excess air. The stoichiometric quantity of air does not include any excess air, as it is the minimum amount required for complete combustion.
**d) Air required to convert CO into CO2**
This option is incorrect because it refers to the air required for the conversion of carbon monoxide (CO) to carbon dioxide (CO2). While air is indeed required for this reaction, it is not the stoichiometric quantity of air, as the stoichiometric quantity is specifically for the complete combustion of the fuel.
**e) Air required to form an explosive mixture**
This option is incorrect because an explosive mixture requires a fuel, oxygen, and an ignition source. The stoichiometric quantity of air is not necessarily related to explosive mixtures, as it is focused on the complete combustion of the fuel rather than the conditions for explosive reactions.
In conclusion, the correct answer is option 'b' - the stoichiometric quantity of air refers to the air required for complete combustion of fuel with no excess air. It is the theoretical amount of air needed to fully react with the fuel and convert it into carbon dioxide and water.
The stoichiometric quantity of air refers to the amount of air required for complete combustion of a fuel with no excess air. It is the theoretical amount of air needed to completely react with all the fuel molecules present, resulting in the complete conversion of fuel to carbon dioxide and water.
**Explanation**
**a) Air present in the atmosphere at NTP conditions**
This option is incorrect because the air present in the atmosphere at normal temperature and pressure (NTP) conditions is not the stoichiometric quantity of air. The air in the atmosphere consists of various gases such as nitrogen, oxygen, carbon dioxide, and traces of other gases, but it does not have a specific stoichiometric ratio.
**b) Air required for complete combustion of fuel with no excess air**
This option is the correct answer. The stoichiometric quantity of air is the exact amount of air required to completely burn a fuel without any excess air. It is based on the chemical reaction between the fuel and oxygen in the air, following the stoichiometric ratio of the reaction equation. This ensures that all the fuel is converted into carbon dioxide and water without any unburned fuel or incomplete combustion products.
**c) Air required for optimum combustion so as to have reasonable excess air**
This option is incorrect because it refers to the air required for optimum combustion, which includes a reasonable amount of excess air. The stoichiometric quantity of air does not include any excess air, as it is the minimum amount required for complete combustion.
**d) Air required to convert CO into CO2**
This option is incorrect because it refers to the air required for the conversion of carbon monoxide (CO) to carbon dioxide (CO2). While air is indeed required for this reaction, it is not the stoichiometric quantity of air, as the stoichiometric quantity is specifically for the complete combustion of the fuel.
**e) Air required to form an explosive mixture**
This option is incorrect because an explosive mixture requires a fuel, oxygen, and an ignition source. The stoichiometric quantity of air is not necessarily related to explosive mixtures, as it is focused on the complete combustion of the fuel rather than the conditions for explosive reactions.
In conclusion, the correct answer is option 'b' - the stoichiometric quantity of air refers to the air required for complete combustion of fuel with no excess air. It is the theoretical amount of air needed to fully react with the fuel and convert it into carbon dioxide and water.
Of all power plants, hydel is more disadvantageous when one compares the- a)nearness to load centre
- b)cost of energy resource
- c)technical skill required
- d)economics that determine the choice of plant
Correct answer is option 'D'. Can you explain this answer?
Of all power plants, hydel is more disadvantageous when one compares the
a)
nearness to load centre
b)
cost of energy resource
c)
technical skill required
d)
economics that determine the choice of plant
|
Atharva Majumdar answered |
The Disadvantages of Hydel Power Plants
Hydel power plants, also known as hydroelectric power plants, generate electricity by harnessing the energy of flowing or falling water. While hydel power plants have several advantages, such as being a renewable energy source and having low operational costs, they also have some disadvantages. Among these disadvantages, the economics of hydel power plants play a significant role in determining their choice as a power generation option.
Economics of Power Plants
The economics of power plants refer to the financial considerations involved in the generation of electricity. This includes the initial capital investment, operational costs, maintenance expenses, and the cost of energy resources used to produce electricity. When comparing different types of power plants, the economics of each option are crucial in determining which plant is more advantageous.
Disadvantages of Hydel Power Plants
1. Capital Investment: The construction of hydel power plants involves significant capital investment. Building dams, reservoirs, and other infrastructure required for generating electricity from hydropower can be expensive. Additionally, the costs associated with acquiring land, environmental impact assessments, and obtaining necessary permits further contribute to the initial investment.
2. Cost of Energy Resource: While water, the energy resource used in hydel power plants, is freely available, the costs associated with harnessing it can be high. The construction and maintenance of dams, tunnels, and other structures necessary for water storage and flow control can incur substantial expenses.
3. Technical Skill Required: The operation and maintenance of hydel power plants require specialized technical skills. Skilled personnel are needed for the efficient operation of the plant, including managing the water flow, maintaining the turbines and generators, and ensuring the safety of the overall system. This requirement for technical expertise can add to the operational costs.
Economics as a Determining Factor
When comparing different power plant options, the economics of each option play a crucial role in decision-making. The economics of power plants are influenced by factors such as initial investment, operational costs, maintenance expenses, and the cost of energy resources. In the case of hydel power plants, the disadvantages mentioned above contribute to their overall economics:
- The high capital investment required for the construction of hydel power plants can make them less economically viable compared to other alternatives.
- The costs associated with harnessing the energy resource, such as building dams and controlling water flow, can further affect the economics of hydel power plants.
- The need for specialized technical skills adds to the operational costs of hydel power plants.
- Considering these factors, the economics of hydel power plants may not be as favorable as other power generation options, making them less advantageous when compared.
Therefore, the correct answer is option 'D' - economics that determine the choice of plant.
Hydel power plants, also known as hydroelectric power plants, generate electricity by harnessing the energy of flowing or falling water. While hydel power plants have several advantages, such as being a renewable energy source and having low operational costs, they also have some disadvantages. Among these disadvantages, the economics of hydel power plants play a significant role in determining their choice as a power generation option.
Economics of Power Plants
The economics of power plants refer to the financial considerations involved in the generation of electricity. This includes the initial capital investment, operational costs, maintenance expenses, and the cost of energy resources used to produce electricity. When comparing different types of power plants, the economics of each option are crucial in determining which plant is more advantageous.
Disadvantages of Hydel Power Plants
1. Capital Investment: The construction of hydel power plants involves significant capital investment. Building dams, reservoirs, and other infrastructure required for generating electricity from hydropower can be expensive. Additionally, the costs associated with acquiring land, environmental impact assessments, and obtaining necessary permits further contribute to the initial investment.
2. Cost of Energy Resource: While water, the energy resource used in hydel power plants, is freely available, the costs associated with harnessing it can be high. The construction and maintenance of dams, tunnels, and other structures necessary for water storage and flow control can incur substantial expenses.
3. Technical Skill Required: The operation and maintenance of hydel power plants require specialized technical skills. Skilled personnel are needed for the efficient operation of the plant, including managing the water flow, maintaining the turbines and generators, and ensuring the safety of the overall system. This requirement for technical expertise can add to the operational costs.
Economics as a Determining Factor
When comparing different power plant options, the economics of each option play a crucial role in decision-making. The economics of power plants are influenced by factors such as initial investment, operational costs, maintenance expenses, and the cost of energy resources. In the case of hydel power plants, the disadvantages mentioned above contribute to their overall economics:
- The high capital investment required for the construction of hydel power plants can make them less economically viable compared to other alternatives.
- The costs associated with harnessing the energy resource, such as building dams and controlling water flow, can further affect the economics of hydel power plants.
- The need for specialized technical skills adds to the operational costs of hydel power plants.
- Considering these factors, the economics of hydel power plants may not be as favorable as other power generation options, making them less advantageous when compared.
Therefore, the correct answer is option 'D' - economics that determine the choice of plant.
Orsat meter is used for- a)gravimetric analysis of the flue gases
- b)volumetric analysis of the flue gases
- c)mass flow of the flue gases
- d)measuring smoke density of flue gases
- e)none of the above
Correct answer is option 'B'. Can you explain this answer?
Orsat meter is used for
a)
gravimetric analysis of the flue gases
b)
volumetric analysis of the flue gases
c)
mass flow of the flue gases
d)
measuring smoke density of flue gases
e)
none of the above
|
|
Ishaan Malik answered |
Orsat Meter for Volumetric Analysis of Flue Gases
Orsat meter is a device that is used for the volumetric analysis of flue gases. It is a gas analyzer that is mainly used for the determination of the composition of the flue gases. It is named after the German chemist H. Orsat who invented it in the late 19th century.
Working Principle
The working principle of the Orsat meter is based on the principle of volumetric analysis. It consists of a series of three absorption bulbs that are filled with different reagents. The first bulb contains a solution of potassium hydroxide (KOH) which is used to absorb carbon dioxide (CO2). The second bulb contains a solution of pyrogallic acid which is used to absorb oxygen (O2). The third bulb contains a solution of sodium hydroxide (NaOH) which is used to absorb sulfur dioxide (SO2).
The flue gas sample is drawn into the Orsat meter using a pump. The gas sample is then passed through the first bulb which absorbs CO2. The second bulb is used to absorb O2 and the third bulb is used to absorb SO2. The volume of each gas absorbed is measured using a graduated burette. The composition of the flue gas is then calculated based on the volume of each gas absorbed.
Applications
The Orsat meter is mainly used in industries that produce flue gas such as power plants, cement plants, and chemical plants. It is used to determine the composition of the flue gases which is important for pollution control and energy efficiency. The Orsat meter is also used in research laboratories for the analysis of gases.
Advantages
- The Orsat meter is a reliable and accurate device for the determination of the composition of flue gases.
- It is easy to use and requires minimal training.
- It is a portable device that can be used in the field for on-site analysis.
Disadvantages
- The Orsat meter is time-consuming compared to other gas analyzers.
- It requires a large sample size which is not always possible in certain situations.
- The reagents used in the Orsat meter can be hazardous and require proper handling and disposal.
Conclusion
In conclusion, the Orsat meter is an important device for the volumetric analysis of flue gases. It provides accurate and reliable results for the determination of the composition of the flue gases. The Orsat meter is widely used in industries that produce flue gases and in research laboratories for the analysis of gases.
Orsat meter is a device that is used for the volumetric analysis of flue gases. It is a gas analyzer that is mainly used for the determination of the composition of the flue gases. It is named after the German chemist H. Orsat who invented it in the late 19th century.
Working Principle
The working principle of the Orsat meter is based on the principle of volumetric analysis. It consists of a series of three absorption bulbs that are filled with different reagents. The first bulb contains a solution of potassium hydroxide (KOH) which is used to absorb carbon dioxide (CO2). The second bulb contains a solution of pyrogallic acid which is used to absorb oxygen (O2). The third bulb contains a solution of sodium hydroxide (NaOH) which is used to absorb sulfur dioxide (SO2).
The flue gas sample is drawn into the Orsat meter using a pump. The gas sample is then passed through the first bulb which absorbs CO2. The second bulb is used to absorb O2 and the third bulb is used to absorb SO2. The volume of each gas absorbed is measured using a graduated burette. The composition of the flue gas is then calculated based on the volume of each gas absorbed.
Applications
The Orsat meter is mainly used in industries that produce flue gas such as power plants, cement plants, and chemical plants. It is used to determine the composition of the flue gases which is important for pollution control and energy efficiency. The Orsat meter is also used in research laboratories for the analysis of gases.
Advantages
- The Orsat meter is a reliable and accurate device for the determination of the composition of flue gases.
- It is easy to use and requires minimal training.
- It is a portable device that can be used in the field for on-site analysis.
Disadvantages
- The Orsat meter is time-consuming compared to other gas analyzers.
- It requires a large sample size which is not always possible in certain situations.
- The reagents used in the Orsat meter can be hazardous and require proper handling and disposal.
Conclusion
In conclusion, the Orsat meter is an important device for the volumetric analysis of flue gases. It provides accurate and reliable results for the determination of the composition of the flue gases. The Orsat meter is widely used in industries that produce flue gases and in research laboratories for the analysis of gases.
In a throttling process- a)steam temperature remains constant
- b)steam pressure remains constant
- c)steam enthalpy remains constant
- d)steam entropy remains constant
- e)steam volume remains constant
Correct answer is option 'C'. Can you explain this answer?
In a throttling process
a)
steam temperature remains constant
b)
steam pressure remains constant
c)
steam enthalpy remains constant
d)
steam entropy remains constant
e)
steam volume remains constant
|
Telecom Tuners answered |
Throttling Process in Thermodynamics:
- Definition: Throttling process is an irreversible adiabatic process in which a fluid undergoes a rapid change in its pressure and temperature without any heat transfer.
- Characteristics:
- Occurs in a constant enthalpy process.
- Results in a decrease in pressure and temperature of the fluid.
Explanation on why Steam Enthalpy remains constant in Throttling Process:
- During a throttling process, the fluid (in this case, steam) experiences a rapid expansion through a valve, causing a drop in pressure and temperature.
- As the process is adiabatic, there is no heat transfer involved, so the enthalpy of the steam remains constant.
- Enthalpy is a measure of the total energy of a system, including internal energy and pressure-volume work done. In a throttling process, the work done is negligible, so the enthalpy remains constant.
- Therefore, in a throttling process, steam enthalpy remains constant while pressure and temperature change.
Conclusion:
- Steam enthalpy remains constant in a throttling process due to the adiabatic and rapid nature of the expansion, which results in no heat transfer and negligible work done.
- Understanding the behavior of steam in throttling processes is crucial for various engineering applications, such as in steam turbines and refrigeration systems.
Superheating of steam is done at- a)constant volume
- b)constant temperature
- c)constant pressure
- d)constant entropy
- e)constant enthalpy
Correct answer is option 'C'. Can you explain this answer?
Superheating of steam is done at
a)
constant volume
b)
constant temperature
c)
constant pressure
d)
constant entropy
e)
constant enthalpy
|
|
Sanskriti Basu answered |
Superheating of Steam at Constant Pressure
Explanation:
- Superheating of steam is the process of heating steam above its saturation temperature at a constant pressure. This is done to increase the energy content of the steam and improve its thermal efficiency in various applications.
- When superheating steam, it is essential to maintain a constant pressure throughout the process. This ensures that the properties of the steam remain consistent and predictable, making it easier to control and utilize in different systems.
- By superheating steam at a constant pressure, the temperature of the steam can be increased without changing its phase from vapor to liquid. This results in steam with higher enthalpy and energy content, making it more suitable for tasks such as driving turbines or heating processes.
- Superheating steam at a constant pressure allows for precise control over the temperature of the steam, which is crucial in applications where specific temperature requirements must be met. This method also ensures that the steam remains in a gaseous state throughout the process, preventing any condensation that could affect performance.
- Overall, superheating steam at a constant pressure is a fundamental step in optimizing the efficiency and effectiveness of steam-based systems, making it a common practice in industries such as power generation, chemical processing, and manufacturing.
Explanation:
- Superheating of steam is the process of heating steam above its saturation temperature at a constant pressure. This is done to increase the energy content of the steam and improve its thermal efficiency in various applications.
- When superheating steam, it is essential to maintain a constant pressure throughout the process. This ensures that the properties of the steam remain consistent and predictable, making it easier to control and utilize in different systems.
- By superheating steam at a constant pressure, the temperature of the steam can be increased without changing its phase from vapor to liquid. This results in steam with higher enthalpy and energy content, making it more suitable for tasks such as driving turbines or heating processes.
- Superheating steam at a constant pressure allows for precise control over the temperature of the steam, which is crucial in applications where specific temperature requirements must be met. This method also ensures that the steam remains in a gaseous state throughout the process, preventing any condensation that could affect performance.
- Overall, superheating steam at a constant pressure is a fundamental step in optimizing the efficiency and effectiveness of steam-based systems, making it a common practice in industries such as power generation, chemical processing, and manufacturing.
The excess air required for combustion of pulverized coal i of the order of- a)100 to 150 %
- b)30 to 60%
- c)15 to 40 %
- d)5 to 10%
Correct answer is option 'C'. Can you explain this answer?
The excess air required for combustion of pulverized coal i of the order of
a)
100 to 150 %
b)
30 to 60%
c)
15 to 40 %
d)
5 to 10%
|
|
Devansh Banerjee answered |
Excess Air Requirement for Combustion of Pulverized Coal
Excess air refers to the additional amount of air supplied to the combustion process beyond what is required for complete combustion of the fuel. In the case of pulverized coal combustion, excess air is necessary to ensure efficient and complete combustion of the coal particles. The excess air requirement for combustion of pulverized coal is typically of the order of 15 to 40%.
1. What is pulverized coal?
- Pulverized coal is coal that has been ground into a fine powder, typically with a particle size of less than 75 micrometers.
- Pulverized coal is commonly used as a fuel in industrial boilers and power plants due to its ease of handling, high combustion efficiency, and low emissions.
2. Combustion process of pulverized coal
- Combustion of pulverized coal involves the rapid oxidation of coal particles in the presence of a sufficient amount of oxygen.
- The combustion process consists of three stages: drying and heating, pyrolysis, and combustion of volatile matter.
- During the combustion process, the coal particles are suspended in a stream of air, and the oxygen in the air reacts with the carbon in the coal to produce carbon dioxide (CO2) and heat.
3. Why is excess air required?
- Excess air is required to ensure complete combustion of the coal particles and to prevent the formation of pollutants such as carbon monoxide (CO) and unburned carbon.
- The excess air provides an adequate supply of oxygen to react with the carbon in the coal, ensuring that all the carbon is oxidized to CO2.
- Excess air also helps in maintaining the required temperature for efficient combustion and prevents the formation of clinkers (solid residues) that can hinder the combustion process.
4. Excess air requirement
- The excess air requirement for combustion of pulverized coal is typically of the order of 15 to 40%.
- This means that the amount of air supplied to the combustion process is 15% to 40% more than the stoichiometric air requirement, which is the theoretical minimum amount of air needed for complete combustion.
- The actual amount of excess air required depends on various factors such as the type and quality of coal, combustion equipment design, and operating conditions.
- The excess air requirement is determined by balancing the need for complete combustion and heat transfer efficiency with the need to minimize air pollutants and optimize energy efficiency.
In conclusion, the excess air requirement for combustion of pulverized coal is typically in the range of 15 to 40%. This additional air supply ensures efficient and complete combustion of the coal particles, preventing the formation of pollutants and maximizing energy conversion.
Excess air refers to the additional amount of air supplied to the combustion process beyond what is required for complete combustion of the fuel. In the case of pulverized coal combustion, excess air is necessary to ensure efficient and complete combustion of the coal particles. The excess air requirement for combustion of pulverized coal is typically of the order of 15 to 40%.
1. What is pulverized coal?
- Pulverized coal is coal that has been ground into a fine powder, typically with a particle size of less than 75 micrometers.
- Pulverized coal is commonly used as a fuel in industrial boilers and power plants due to its ease of handling, high combustion efficiency, and low emissions.
2. Combustion process of pulverized coal
- Combustion of pulverized coal involves the rapid oxidation of coal particles in the presence of a sufficient amount of oxygen.
- The combustion process consists of three stages: drying and heating, pyrolysis, and combustion of volatile matter.
- During the combustion process, the coal particles are suspended in a stream of air, and the oxygen in the air reacts with the carbon in the coal to produce carbon dioxide (CO2) and heat.
3. Why is excess air required?
- Excess air is required to ensure complete combustion of the coal particles and to prevent the formation of pollutants such as carbon monoxide (CO) and unburned carbon.
- The excess air provides an adequate supply of oxygen to react with the carbon in the coal, ensuring that all the carbon is oxidized to CO2.
- Excess air also helps in maintaining the required temperature for efficient combustion and prevents the formation of clinkers (solid residues) that can hinder the combustion process.
4. Excess air requirement
- The excess air requirement for combustion of pulverized coal is typically of the order of 15 to 40%.
- This means that the amount of air supplied to the combustion process is 15% to 40% more than the stoichiometric air requirement, which is the theoretical minimum amount of air needed for complete combustion.
- The actual amount of excess air required depends on various factors such as the type and quality of coal, combustion equipment design, and operating conditions.
- The excess air requirement is determined by balancing the need for complete combustion and heat transfer efficiency with the need to minimize air pollutants and optimize energy efficiency.
In conclusion, the excess air requirement for combustion of pulverized coal is typically in the range of 15 to 40%. This additional air supply ensures efficient and complete combustion of the coal particles, preventing the formation of pollutants and maximizing energy conversion.
Forced draught fans of a large steam generator have- a)Backward curved blades
- b)Forward curved blades
- c)Straight or radial blades
- d)Double curved blades
Correct answer is option 'A'. Can you explain this answer?
Forced draught fans of a large steam generator have
a)
Backward curved blades
b)
Forward curved blades
c)
Straight or radial blades
d)
Double curved blades
|
|
Soumya Basak answered |
Backward curved blades
- Forced draught fans of a large steam generator typically have backward curved blades.
- These blades are designed to efficiently move large volumes of air at high pressures.
- The backward curved blades are ideal for applications where the fan needs to overcome high resistance or back pressure.
- These blades are curved in the direction opposite to the direction of rotation, which helps in reducing turbulence and noise.
- The design of these blades also allows for higher efficiency and lower power consumption compared to other blade types.
- In the case of large steam generators, where a significant amount of air needs to be circulated, the backward curved blades are preferred for their performance characteristics.
Overall, the use of backward curved blades in forced draught fans of large steam generators ensures efficient operation and optimal performance in moving air at high pressures.
Carbonisation of coal is the process of- a)pulverising coal in inert atmosphere
- b)heating wood in a limited supply of air at temperatures below 300ºC
- c)strongly heating coal continuously or about 48 hours in the absence of air in a closed vessel
- d)binding the pulverised coal into bricketters
- e)enriching carbon in the coal
Correct answer is option 'C'. Can you explain this answer?
Carbonisation of coal is the process of
a)
pulverising coal in inert atmosphere
b)
heating wood in a limited supply of air at temperatures below 300ºC
c)
strongly heating coal continuously or about 48 hours in the absence of air in a closed vessel
d)
binding the pulverised coal into bricketters
e)
enriching carbon in the coal
|
|
Gaurav Kapoor answered |
Carbonisation of Coal
Carbonisation of coal is a process in which coal is converted into coke by strongly heating it continuously or about 48 hours in the absence of air in a closed vessel. This process is also known as destructive distillation of coal.
Steps Involved in Carbonisation of Coal
The process of carbonisation of coal involves the following steps:
1. Preparation of Coal
The coal is first cleaned and sorted to remove any impurities and stones. It is then crushed into small pieces and passed through a sieve to obtain a uniform size.
2. Charging the Coal
The prepared coal is then charged into a carbonisation retort, which is a closed vessel made up of fire clay bricks. The retort is connected to a condenser for the collection of by-products.
3. Heating the Coal
The coal is heated strongly in the retort at a temperature of about 1200°C. The process of heating is carried out in the absence of air or any other oxidising agent to prevent combustion of coal.
4. Collection of By-Products
During the process of carbonisation, various by-products such as coal gas, tar, and ammonia are obtained. These by-products are collected and stored separately for further processing and use.
5. Formation of Coke
As a result of the heating process, the coal is converted into coke, which is a hard, porous, and carbon-rich substance. The coke is then cooled and removed from the retort.
Uses of Coke
Coke is widely used in various industries for the following purposes:
1. As a fuel in blast furnaces for the production of iron and steel.
2. As a reducing agent in chemical processes.
3. As a fuel for heating and cooking purposes.
4. As a filter medium in water treatment plants.
Conclusion
Carbonisation of coal is an important process for the production of coke, which is widely used in various industries. The process involves the heating of coal in a closed vessel at a high temperature in the absence of air to obtain coke and various by-products.
Carbonisation of coal is a process in which coal is converted into coke by strongly heating it continuously or about 48 hours in the absence of air in a closed vessel. This process is also known as destructive distillation of coal.
Steps Involved in Carbonisation of Coal
The process of carbonisation of coal involves the following steps:
1. Preparation of Coal
The coal is first cleaned and sorted to remove any impurities and stones. It is then crushed into small pieces and passed through a sieve to obtain a uniform size.
2. Charging the Coal
The prepared coal is then charged into a carbonisation retort, which is a closed vessel made up of fire clay bricks. The retort is connected to a condenser for the collection of by-products.
3. Heating the Coal
The coal is heated strongly in the retort at a temperature of about 1200°C. The process of heating is carried out in the absence of air or any other oxidising agent to prevent combustion of coal.
4. Collection of By-Products
During the process of carbonisation, various by-products such as coal gas, tar, and ammonia are obtained. These by-products are collected and stored separately for further processing and use.
5. Formation of Coke
As a result of the heating process, the coal is converted into coke, which is a hard, porous, and carbon-rich substance. The coke is then cooled and removed from the retort.
Uses of Coke
Coke is widely used in various industries for the following purposes:
1. As a fuel in blast furnaces for the production of iron and steel.
2. As a reducing agent in chemical processes.
3. As a fuel for heating and cooking purposes.
4. As a filter medium in water treatment plants.
Conclusion
Carbonisation of coal is an important process for the production of coke, which is widely used in various industries. The process involves the heating of coal in a closed vessel at a high temperature in the absence of air to obtain coke and various by-products.
Heating of dry stream above saturation temperature is known as- a)enthalpy
- b)superheating
- c)supersaturation
- d)latent heat
- e)super tempering
Correct answer is option 'B'. Can you explain this answer?
Heating of dry stream above saturation temperature is known as
a)
enthalpy
b)
superheating
c)
supersaturation
d)
latent heat
e)
super tempering
|
Srestha Datta answered |
Superheating
Superheating refers to the process of heating a substance above its saturation temperature without changing its phase from a gas to a liquid. In the context of a dry stream, superheating occurs when the steam is heated to a temperature above its saturation temperature.
Explanation:
1. Saturation Temperature:
The saturation temperature is the temperature at which a substance changes phase from a liquid to a vapor at a given pressure. For water, the saturation temperature increases with pressure. At the saturation temperature, the substance exists in equilibrium between its liquid and vapor phases.
2. Dry Stream:
A dry stream is a term used to describe steam that is completely vaporized and contains no liquid droplets. It is a superheated vapor.
3. Heating above Saturation Temperature:
When a dry stream is heated above its saturation temperature, it is referred to as superheating. This occurs when additional heat is added to the steam after it has already reached its saturation temperature.
4. Purpose of Superheating:
Superheating is often done to increase the energy content or temperature of the steam. Superheated steam has several advantages in various applications, such as:
- Improved energy transfer in heat exchangers
- Increased efficiency in steam turbines
- Reduced erosion and corrosion in steam pipes
5. Enthalpy, Supersaturation, and Latent Heat:
- Enthalpy (option A) is a thermodynamic property that represents the total energy of a substance, including internal energy and pressure-volume work. While superheating affects the enthalpy of the steam, it specifically refers to heating above the saturation temperature.
- Supersaturation (option C) refers to a state in which a solution contains more solute than it can normally dissolve at a given temperature and pressure. It is not applicable to the heating of a dry stream.
- Latent heat (option D) is the heat energy required to change the phase of a substance without changing its temperature. It is relevant to phase changes, such as the transition from a liquid to a vapor, but not to superheating.
Conclusion:
In the context of a dry stream, heating above the saturation temperature is known as superheating. This process increases the energy content and temperature of the steam, making it useful for various applications in industries such as power generation and heating systems.
Superheating refers to the process of heating a substance above its saturation temperature without changing its phase from a gas to a liquid. In the context of a dry stream, superheating occurs when the steam is heated to a temperature above its saturation temperature.
Explanation:
1. Saturation Temperature:
The saturation temperature is the temperature at which a substance changes phase from a liquid to a vapor at a given pressure. For water, the saturation temperature increases with pressure. At the saturation temperature, the substance exists in equilibrium between its liquid and vapor phases.
2. Dry Stream:
A dry stream is a term used to describe steam that is completely vaporized and contains no liquid droplets. It is a superheated vapor.
3. Heating above Saturation Temperature:
When a dry stream is heated above its saturation temperature, it is referred to as superheating. This occurs when additional heat is added to the steam after it has already reached its saturation temperature.
4. Purpose of Superheating:
Superheating is often done to increase the energy content or temperature of the steam. Superheated steam has several advantages in various applications, such as:
- Improved energy transfer in heat exchangers
- Increased efficiency in steam turbines
- Reduced erosion and corrosion in steam pipes
5. Enthalpy, Supersaturation, and Latent Heat:
- Enthalpy (option A) is a thermodynamic property that represents the total energy of a substance, including internal energy and pressure-volume work. While superheating affects the enthalpy of the steam, it specifically refers to heating above the saturation temperature.
- Supersaturation (option C) refers to a state in which a solution contains more solute than it can normally dissolve at a given temperature and pressure. It is not applicable to the heating of a dry stream.
- Latent heat (option D) is the heat energy required to change the phase of a substance without changing its temperature. It is relevant to phase changes, such as the transition from a liquid to a vapor, but not to superheating.
Conclusion:
In the context of a dry stream, heating above the saturation temperature is known as superheating. This process increases the energy content and temperature of the steam, making it useful for various applications in industries such as power generation and heating systems.
In a throttling process- a)heat transfer takes place
- b)work is done by the expanding steam
- c)internal energy of steam changes
- d)all of the above
- e)none of the above
Correct answer is option 'E'. Can you explain this answer?
In a throttling process
a)
heat transfer takes place
b)
work is done by the expanding steam
c)
internal energy of steam changes
d)
all of the above
e)
none of the above
|
|
Tarun Chatterjee answered |
Throttling Process in Thermodynamics
A throttling process is an isenthalpic process in which the enthalpy of the fluid or gas remains constant. During the throttling process, the fluid or gas passes through a restriction such as a valve or a narrow opening, which leads to a decrease in pressure and an increase in velocity. This process is commonly used in steam turbines, refrigeration systems, and gas pipelines.
Explanation of Options
a) Heat transfer takes place: In a throttling process, there is no heat transfer between the system and the surroundings. The process is adiabatic, meaning there is no exchange of heat energy.
b) Work is done by the expanding steam: In a throttling process, the steam or fluid expands due to the decrease in pressure, but no work is done by the system. This is because the process is isenthalpic, and the enthalpy remains constant.
c) Internal energy of steam changes: In a throttling process, the internal energy of the steam or fluid remains constant. This is because the process is adiabatic, and there is no exchange of heat energy.
d) All of the above: None of the options are correct, therefore this option is also incorrect.
e) None of the above: This is the correct option as none of the above options are correct.
Conclusion
In conclusion, a throttling process is an isenthalpic and adiabatic process in which there is no exchange of heat energy and no work is done by the system. Therefore, the correct answer to the given question is option 'E' i.e. none of the above.
A throttling process is an isenthalpic process in which the enthalpy of the fluid or gas remains constant. During the throttling process, the fluid or gas passes through a restriction such as a valve or a narrow opening, which leads to a decrease in pressure and an increase in velocity. This process is commonly used in steam turbines, refrigeration systems, and gas pipelines.
Explanation of Options
a) Heat transfer takes place: In a throttling process, there is no heat transfer between the system and the surroundings. The process is adiabatic, meaning there is no exchange of heat energy.
b) Work is done by the expanding steam: In a throttling process, the steam or fluid expands due to the decrease in pressure, but no work is done by the system. This is because the process is isenthalpic, and the enthalpy remains constant.
c) Internal energy of steam changes: In a throttling process, the internal energy of the steam or fluid remains constant. This is because the process is adiabatic, and there is no exchange of heat energy.
d) All of the above: None of the options are correct, therefore this option is also incorrect.
e) None of the above: This is the correct option as none of the above options are correct.
Conclusion
In conclusion, a throttling process is an isenthalpic and adiabatic process in which there is no exchange of heat energy and no work is done by the system. Therefore, the correct answer to the given question is option 'E' i.e. none of the above.
Sublimation region is the region where- a)solid and vapour phases are in equilibrium
- b)solid and liquid phases are in equilibrium
- c)liquid and vapour phases are in equilibrium
- d)solid, liquid and vapour phases are in equilibrium
- e)none of the above
Correct answer is option 'A'. Can you explain this answer?
Sublimation region is the region where
a)
solid and vapour phases are in equilibrium
b)
solid and liquid phases are in equilibrium
c)
liquid and vapour phases are in equilibrium
d)
solid, liquid and vapour phases are in equilibrium
e)
none of the above
|
|
Divya Banerjee answered |
**Sublimation Region**
The sublimation region refers to the phase diagram where solid and vapor phases are in equilibrium. This means that under specific conditions of temperature and pressure, a solid substance can directly transition into a vapor without passing through the liquid phase.
**Explanation:**
**Phase Diagram:**
A phase diagram is a graphical representation of the different phases (solid, liquid, and vapor) of a substance under various conditions of temperature and pressure. It shows the regions where two phases coexist in equilibrium and the boundaries between these regions.
**Triple Point:**
The triple point is the point on a phase diagram where all three phases (solid, liquid, and vapor) coexist in equilibrium. At this point, the substance can exist in any of the three phases depending on the temperature and pressure conditions.
**Sublimation:**
Sublimation is the process by which a solid substance directly transitions into a vapor phase without passing through the liquid phase. This occurs when the temperature and pressure conditions are within the sublimation region on the phase diagram.
**Equilibrium between Solid and Vapor:**
In the sublimation region, the solid and vapor phases of a substance are in equilibrium. This means that there is a balance between the rate of sublimation (solid to vapor) and the rate of deposition (vapor to solid). The substance exists simultaneously as both a solid and a vapor, with the amount of each phase dependent on the specific temperature and pressure conditions.
**Conditions for Sublimation:**
Sublimation can occur under specific conditions of temperature and pressure. The temperature must be below the substance's melting point (where it would transition from solid to liquid) and above its boiling point (where it would transition from liquid to vapor). The pressure should be below the substance's vapor pressure at that temperature.
**Example:**
A common example of a substance that exhibits sublimation is dry ice (solid carbon dioxide). At atmospheric pressure, dry ice sublimes at a temperature of -78.5°C, directly transitioning from a solid to a vapor without becoming a liquid. This is why dry ice appears to "disappear" as it sublimes.
In conclusion, the sublimation region on a phase diagram refers to the region where solid and vapor phases are in equilibrium. Substances in this region can undergo sublimation, transitioning directly from a solid to a vapor phase without passing through the liquid phase.
The sublimation region refers to the phase diagram where solid and vapor phases are in equilibrium. This means that under specific conditions of temperature and pressure, a solid substance can directly transition into a vapor without passing through the liquid phase.
**Explanation:**
**Phase Diagram:**
A phase diagram is a graphical representation of the different phases (solid, liquid, and vapor) of a substance under various conditions of temperature and pressure. It shows the regions where two phases coexist in equilibrium and the boundaries between these regions.
**Triple Point:**
The triple point is the point on a phase diagram where all three phases (solid, liquid, and vapor) coexist in equilibrium. At this point, the substance can exist in any of the three phases depending on the temperature and pressure conditions.
**Sublimation:**
Sublimation is the process by which a solid substance directly transitions into a vapor phase without passing through the liquid phase. This occurs when the temperature and pressure conditions are within the sublimation region on the phase diagram.
**Equilibrium between Solid and Vapor:**
In the sublimation region, the solid and vapor phases of a substance are in equilibrium. This means that there is a balance between the rate of sublimation (solid to vapor) and the rate of deposition (vapor to solid). The substance exists simultaneously as both a solid and a vapor, with the amount of each phase dependent on the specific temperature and pressure conditions.
**Conditions for Sublimation:**
Sublimation can occur under specific conditions of temperature and pressure. The temperature must be below the substance's melting point (where it would transition from solid to liquid) and above its boiling point (where it would transition from liquid to vapor). The pressure should be below the substance's vapor pressure at that temperature.
**Example:**
A common example of a substance that exhibits sublimation is dry ice (solid carbon dioxide). At atmospheric pressure, dry ice sublimes at a temperature of -78.5°C, directly transitioning from a solid to a vapor without becoming a liquid. This is why dry ice appears to "disappear" as it sublimes.
In conclusion, the sublimation region on a phase diagram refers to the region where solid and vapor phases are in equilibrium. Substances in this region can undergo sublimation, transitioning directly from a solid to a vapor phase without passing through the liquid phase.
The draught in locomotive boilers is produced by- a)Chimney
- b)Centrifugal fan
- c)Steam jet
- d)Locomotion
Correct answer is option 'C'. Can you explain this answer?
The draught in locomotive boilers is produced by
a)
Chimney
b)
Centrifugal fan
c)
Steam jet
d)
Locomotion
|
|
Bibek Das answered |
The draught in locomotive boilers is produced by a steam jet. This is the correct answer because steam jets are commonly used in locomotive boilers to create a draught or draft, which is the flow of air through the boiler and chimney. The draught is necessary to maintain combustion and ensure efficient operation of the boiler.
Here is a detailed explanation of how a steam jet produces draught in locomotive boilers:
1. Purpose of draught in locomotive boilers:
- The primary purpose of draught in locomotive boilers is to supply the necessary oxygen for combustion and remove the combustion products (such as flue gases) from the boiler.
- It also helps in maintaining the required pressure inside the boiler and ensures the proper flow of gases through the chimney.
2. Steam jet as a method of producing draught:
- In a locomotive boiler, a steam jet is used to create the draught.
- The steam jet is created by injecting high-pressure steam into a nozzle or diffuser.
- As the steam expands through the nozzle, it creates a high-velocity jet of steam.
- This high-velocity steam jet creates a low-pressure area around it, which in turn creates a pressure difference between the inside and outside of the boiler.
- This pressure difference creates a flow of air through the boiler and chimney, thereby producing the draught.
3. Advantages of using a steam jet:
- Steam jets are simple and reliable devices for creating draught in locomotive boilers.
- They do not require any moving parts or external power sources, making them easy to maintain and operate.
- Steam jets can provide a strong draught, ensuring efficient combustion and better boiler performance.
In conclusion, the draught in locomotive boilers is produced by a steam jet. The steam jet creates a low-pressure area that induces the flow of air through the boiler and chimney, maintaining combustion and ensuring efficient operation of the boiler.
Here is a detailed explanation of how a steam jet produces draught in locomotive boilers:
1. Purpose of draught in locomotive boilers:
- The primary purpose of draught in locomotive boilers is to supply the necessary oxygen for combustion and remove the combustion products (such as flue gases) from the boiler.
- It also helps in maintaining the required pressure inside the boiler and ensures the proper flow of gases through the chimney.
2. Steam jet as a method of producing draught:
- In a locomotive boiler, a steam jet is used to create the draught.
- The steam jet is created by injecting high-pressure steam into a nozzle or diffuser.
- As the steam expands through the nozzle, it creates a high-velocity jet of steam.
- This high-velocity steam jet creates a low-pressure area around it, which in turn creates a pressure difference between the inside and outside of the boiler.
- This pressure difference creates a flow of air through the boiler and chimney, thereby producing the draught.
3. Advantages of using a steam jet:
- Steam jets are simple and reliable devices for creating draught in locomotive boilers.
- They do not require any moving parts or external power sources, making them easy to maintain and operate.
- Steam jets can provide a strong draught, ensuring efficient combustion and better boiler performance.
In conclusion, the draught in locomotive boilers is produced by a steam jet. The steam jet creates a low-pressure area that induces the flow of air through the boiler and chimney, maintaining combustion and ensuring efficient operation of the boiler.
Chapter doubts & questions for Power Plant Engineering - Mechanical Engineering SSC JE (Technical) 2025 is part of Mechanical Engineering exam preparation. The chapters have been prepared according to the Mechanical Engineering exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Mechanical Engineering 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
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Mechanical Engineering SSC JE (Technical)
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