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All questions of Refrigeration & Air Conditioning for Mechanical Engineering Exam
The Coefficient of Performance of a domestic refrigerator is- a)less than 1
- b)more than 1
- c)equal to 1
- d)dependent upon the mass of the refrigerant
Correct answer is option 'B'. Can you explain this answer?
The Coefficient of Performance of a domestic refrigerator is
a)
less than 1
b)
more than 1
c)
equal to 1
d)
dependent upon the mass of the refrigerant
|
Bijoy Kapoor answered |
The coefficient of performance (COP) is a measure of efficiency of the refrigerator. The COP of a domestic refrigerator is the ratio of the refrigeration capacity to the energy supplied to the compressor. It can be expressed by equation.
In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the- a)expansion valve to the evaporator
- b)evaporator to the thermostat
- c)condenser to the expansion valve
- d)condenser to the evaporator
Correct answer is option 'A'. Can you explain this answer?
In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the
a)
expansion valve to the evaporator
b)
evaporator to the thermostat
c)
condenser to the expansion valve
d)
condenser to the evaporator
|
Baishali Bajaj answered |
The answer D is correct.
The capillary tube itself serves the purpose of the expansion device, Also, capillary tube is used in small capacity units, where load variation is almost constant, so domestic refrigerator doesn't require the control of the flow of refrigerant.
The capillary tube itself serves the purpose of the expansion device, Also, capillary tube is used in small capacity units, where load variation is almost constant, so domestic refrigerator doesn't require the control of the flow of refrigerant.
The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.- a)same
- b) less
- c)more
- d)none
Correct answer is option 'B'. Can you explain this answer?
The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.
a)
same
b)
less
c)
more
d)
none
|
Ss V answered |
Is less....becz refer work only for cooling so it need to do less compressor work but in case of AC it ll cooling also but at a same time it also work to maintain humidity means it's compressor work against water also..so AC need more work as an input so it ll give proper output.and refer work at constant environment condition means if we place hot water inside refer than it's temp decrease continuously but in AC the room condition is change with surrounding once means same time cloudy same time sunny or rainy so it's need to maintain all ths criteria with in limit so it's cop is more.
Superheating in refrigeration cycle- a)increases COP
- b)decreases COP
- c)doesn’t alter COP
- d)none of these
Correct answer is option 'B'. Can you explain this answer?
Superheating in refrigeration cycle
a)
increases COP
b)
decreases COP
c)
doesn’t alter COP
d)
none of these
|
Rajeev Sharma answered |
In the refrigeration cycle, subcooling is an important process that ensures liquid refrigerant enters the expansion device. Key takeaways: superheat occurs in the evaporator to protect the compressor, and subcooling occurs in the condenser to protect the device.decreases COP.
Horse power and kW required per tonne of refrigeration is expressed as- a)
- b)
- c)4.75 × COP and 3.5 COP
- d)
Correct answer is option 'A'. Can you explain this answer?
Horse power and kW required per tonne of refrigeration is expressed as
a)
b)
c)
4.75 × COP and 3.5 COP
d)
|
Constructing Careers answered |
Horse power per ton = 4.75?COP
1 kW/ton = 3.516/COP
The relative coefficient of performance is- a)actual COP/theoretical COP
- b)theoretical COP/actual COP
- c)actual COP × theoretical COP
- d)1-actual COP × theoretical COP
Correct answer is option 'A'. Can you explain this answer?
The relative coefficient of performance is
a)
actual COP/theoretical COP
b)
theoretical COP/actual COP
c)
actual COP × theoretical COP
d)
1-actual COP × theoretical COP
|
Aditya Deshmukh answered |
A cooling system usually has heat loss during the operation. So its C.O.P is always slightly different from its theoretical C.O.P., the new C.O.P. is known as Actual C.O.P. Relative coefficient of performance defined as the ratio of actual C.O.P. to the theoretical C.O.P.
One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice- a)in 1 hour
- b)in 1 minute
- c)in 24 hours
- d)in 12 hours
- e)in 10 hours
Correct answer is option 'C'. Can you explain this answer?
One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice
a)
in 1 hour
b)
in 1 minute
c)
in 24 hours
d)
in 12 hours
e)
in 10 hours
|
Rahul Chauhan answered |
Explanation:
One ton of refrigeration is a unit of measure used to describe the refrigeration capacity of an air conditioning system or refrigeration system. It is defined as the amount of cooling effect produced by melting one ton of ice in a 24-hour period. Let's break this down further:
- What is a ton of refrigeration?
A ton of refrigeration is a unit of measure that describes the amount of heat that must be removed from a room or a space to lower the temperature by one degree Fahrenheit. This is equivalent to 12,000 BTUs (British Thermal Units) per hour.
- What is the refrigeration effect of melting 1000 kg of ice?
When 1000 kg of ice is melted, it absorbs 334,000 J of heat energy. This is known as the latent heat of fusion.
- How are these two related?
Since one ton of refrigeration is equal to 12,000 BTUs or 3.517 kW of cooling capacity, we can calculate the amount of ice that can be melted in 24 hours using this formula:
Refrigeration effect = 3.517 kW x 24 hours = 84.4 kWh
Ice melted = 84.4 kWh / 334,000 J/kg = 252.7 kg
Therefore, one ton of refrigeration is equal to the refrigeration effect corresponding to melting of 252.7 kg of ice in 24 hours.
- Why is the correct answer option C?
Option C states that one ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice in 24 hours, which is correct based on the calculations above. The other options are incorrect because they either refer to a shorter or longer period of time, which would result in a different amount of ice being melted.
One ton of refrigeration is a unit of measure used to describe the refrigeration capacity of an air conditioning system or refrigeration system. It is defined as the amount of cooling effect produced by melting one ton of ice in a 24-hour period. Let's break this down further:
- What is a ton of refrigeration?
A ton of refrigeration is a unit of measure that describes the amount of heat that must be removed from a room or a space to lower the temperature by one degree Fahrenheit. This is equivalent to 12,000 BTUs (British Thermal Units) per hour.
- What is the refrigeration effect of melting 1000 kg of ice?
When 1000 kg of ice is melted, it absorbs 334,000 J of heat energy. This is known as the latent heat of fusion.
- How are these two related?
Since one ton of refrigeration is equal to 12,000 BTUs or 3.517 kW of cooling capacity, we can calculate the amount of ice that can be melted in 24 hours using this formula:
Refrigeration effect = 3.517 kW x 24 hours = 84.4 kWh
Ice melted = 84.4 kWh / 334,000 J/kg = 252.7 kg
Therefore, one ton of refrigeration is equal to the refrigeration effect corresponding to melting of 252.7 kg of ice in 24 hours.
- Why is the correct answer option C?
Option C states that one ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice in 24 hours, which is correct based on the calculations above. The other options are incorrect because they either refer to a shorter or longer period of time, which would result in a different amount of ice being melted.
The COP of a Carnot refrigeration cycle decreases on- a)decreasing the difference in operating temperatures
- b)keeping the upper temperature constant and increasing the lower temperature
- c)increasing the upper temperature and keeping the lower temperature constant
- d)increasing the upper temperature and decreasing the lower temperature
Correct answer is option 'D'. Can you explain this answer?
The COP of a Carnot refrigeration cycle decreases on
a)
decreasing the difference in operating temperatures
b)
keeping the upper temperature constant and increasing the lower temperature
c)
increasing the upper temperature and keeping the lower temperature constant
d)
increasing the upper temperature and decreasing the lower temperature
|
|
Rajeev Sharma answered |
OPTION D IS CORRECT.
Which one of the following sequence is correct in vapour compression cycle- a)iso-enthalpic expansion, iso-baricheat rejection, isentropic compression, iso-baric heat absorption
- b)iso-entropic compression, iso-baric heat rejection, iso-enthalpic expansion, iso-baric heat absorption
- c)iso-baric heat absorption, isentropic compress, iso-baric heat rejection, iso enthalpic expansion
- d)iso-enthalpic expansion, iso-baric heat absorption isentropic compression, isobaric heat rejection
Correct answer is option 'B'. Can you explain this answer?
Which one of the following sequence is correct in vapour compression cycle
a)
iso-enthalpic expansion, iso-baricheat rejection, isentropic compression, iso-baric heat absorption
b)
iso-entropic compression, iso-baric heat rejection, iso-enthalpic expansion, iso-baric heat absorption
c)
iso-baric heat absorption, isentropic compress, iso-baric heat rejection, iso enthalpic expansion
d)
iso-enthalpic expansion, iso-baric heat absorption isentropic compression, isobaric heat rejection
|
Diya Dasgupta answered |
Vapour Compression Cycle
The vapour compression cycle is a thermodynamic cycle used in refrigeration and air conditioning systems. It involves the compression and expansion of a refrigerant to absorb and release heat, respectively. The cycle consists of four processes:
1. Iso-entropic Compression
2. Iso-baric Heat Rejection
3. Iso-enthalpic Expansion
4. Iso-baric Heat Absorption
Correct Sequence
The correct sequence for the vapour compression cycle is:
B) Iso-entropic Compression, Iso-baric Heat Rejection, Iso-enthalpic Expansion, Iso-baric Heat Absorption
Explanation
1. Iso-entropic Compression: The refrigerant gas is compressed by the compressor. This process is isentropic, meaning it occurs without any heat transfer. The temperature and pressure of the refrigerant increase.
2. Iso-baric Heat Rejection: The high-pressure refrigerant gas is then cooled by rejecting heat to the surrounding environment. This process occurs at constant pressure (iso-baric). The temperature of the refrigerant decreases, but the pressure remains constant.
3. Iso-enthalpic Expansion: The refrigerant is expanded through a valve or an orifice. This process occurs at constant enthalpy (iso-enthalpic), meaning there is no change in the internal energy of the refrigerant. The pressure and temperature of the refrigerant decrease.
4. Iso-baric Heat Absorption: The low-pressure refrigerant gas absorbs heat from the surrounding environment, such as the inside of a refrigerator or air conditioning unit. This process occurs at constant pressure (iso-baric). The temperature of the refrigerant increases, but the pressure remains constant.
Conclusion
In summary, the correct sequence for the vapour compression cycle is iso-entropic compression, iso-baric heat rejection, iso-enthalpic expansion, and iso-baric heat absorption. This cycle is essential for refrigeration and air conditioning systems that require the transfer of heat from one location to another.
The vapour compression cycle is a thermodynamic cycle used in refrigeration and air conditioning systems. It involves the compression and expansion of a refrigerant to absorb and release heat, respectively. The cycle consists of four processes:
1. Iso-entropic Compression
2. Iso-baric Heat Rejection
3. Iso-enthalpic Expansion
4. Iso-baric Heat Absorption
Correct Sequence
The correct sequence for the vapour compression cycle is:
B) Iso-entropic Compression, Iso-baric Heat Rejection, Iso-enthalpic Expansion, Iso-baric Heat Absorption
Explanation
1. Iso-entropic Compression: The refrigerant gas is compressed by the compressor. This process is isentropic, meaning it occurs without any heat transfer. The temperature and pressure of the refrigerant increase.
2. Iso-baric Heat Rejection: The high-pressure refrigerant gas is then cooled by rejecting heat to the surrounding environment. This process occurs at constant pressure (iso-baric). The temperature of the refrigerant decreases, but the pressure remains constant.
3. Iso-enthalpic Expansion: The refrigerant is expanded through a valve or an orifice. This process occurs at constant enthalpy (iso-enthalpic), meaning there is no change in the internal energy of the refrigerant. The pressure and temperature of the refrigerant decrease.
4. Iso-baric Heat Absorption: The low-pressure refrigerant gas absorbs heat from the surrounding environment, such as the inside of a refrigerator or air conditioning unit. This process occurs at constant pressure (iso-baric). The temperature of the refrigerant increases, but the pressure remains constant.
Conclusion
In summary, the correct sequence for the vapour compression cycle is iso-entropic compression, iso-baric heat rejection, iso-enthalpic expansion, and iso-baric heat absorption. This cycle is essential for refrigeration and air conditioning systems that require the transfer of heat from one location to another.
In a vapour compression cycle, the refrigerant immediately after expansion valve is- a)Saturated liquid
- b)Sub-cooled liquid
- c)Wet vapour
- d)Dry vapour
Correct answer is option 'C'. Can you explain this answer?
In a vapour compression cycle, the refrigerant immediately after expansion valve is
a)
Saturated liquid
b)
Sub-cooled liquid
c)
Wet vapour
d)
Dry vapour
|
Bhavya Ahuja answered |
Vapour Compression Cycle and Expansion Valve
Vapour Compression Cycle:
The vapour compression cycle is a refrigeration cycle that is widely used in air conditioning and refrigeration systems. It is a closed cycle that involves the circulation of a refrigerant through various components that change its state from a low-pressure gas to a high-pressure liquid and back to a low-pressure gas.
Expansion Valve:
The expansion valve is an important component in the vapour compression cycle. Its primary function is to reduce the pressure of the refrigerant as it leaves the condenser, which results in a drop in temperature and a change in the state of the refrigerant.
State of Refrigerant after Expansion Valve:
The state of the refrigerant immediately after the expansion valve is crucial in determining the efficiency of the cycle. The state of the refrigerant can be determined by analyzing its pressure and temperature.
Wet Vapour:
The correct answer to the given question is option 'C', which states that the refrigerant immediately after the expansion valve is a wet vapour. A wet vapour is a mixture of liquid and vapour refrigerant. The refrigerant at this stage is at a low temperature and low pressure, and some of it has already condensed into a liquid, while the rest remains in a vapour state.
Importance of Wet Vapour:
The wet vapour state is important because it allows the refrigerant to absorb heat from the evaporator and vaporize completely, which results in a more efficient cycle. If the refrigerant were in a saturated liquid state, it would not be able to absorb heat effectively, and the cycle would be less efficient. If the refrigerant were in a dry vapour state, it would not be able to transfer heat effectively, and the cycle would also be less efficient.
Therefore, it is important to maintain the refrigerant in a wet vapour state immediately after the expansion valve to ensure the efficiency of the cycle.
Vapour Compression Cycle:
The vapour compression cycle is a refrigeration cycle that is widely used in air conditioning and refrigeration systems. It is a closed cycle that involves the circulation of a refrigerant through various components that change its state from a low-pressure gas to a high-pressure liquid and back to a low-pressure gas.
Expansion Valve:
The expansion valve is an important component in the vapour compression cycle. Its primary function is to reduce the pressure of the refrigerant as it leaves the condenser, which results in a drop in temperature and a change in the state of the refrigerant.
State of Refrigerant after Expansion Valve:
The state of the refrigerant immediately after the expansion valve is crucial in determining the efficiency of the cycle. The state of the refrigerant can be determined by analyzing its pressure and temperature.
Wet Vapour:
The correct answer to the given question is option 'C', which states that the refrigerant immediately after the expansion valve is a wet vapour. A wet vapour is a mixture of liquid and vapour refrigerant. The refrigerant at this stage is at a low temperature and low pressure, and some of it has already condensed into a liquid, while the rest remains in a vapour state.
Importance of Wet Vapour:
The wet vapour state is important because it allows the refrigerant to absorb heat from the evaporator and vaporize completely, which results in a more efficient cycle. If the refrigerant were in a saturated liquid state, it would not be able to absorb heat effectively, and the cycle would be less efficient. If the refrigerant were in a dry vapour state, it would not be able to transfer heat effectively, and the cycle would also be less efficient.
Therefore, it is important to maintain the refrigerant in a wet vapour state immediately after the expansion valve to ensure the efficiency of the cycle.
Which one of the following is correct relation between (COP)HP and (COP)R- a)(COP)HP – (COP)R = 1
- b)(COP)R – (COP)HP = 1
- c)(COP)HP + (COP)R = 1
- d)(COP)HP + (COP)R = 0
Correct answer is option 'A'. Can you explain this answer?
Which one of the following is correct relation between (COP)HP and (COP)R
a)
(COP)HP – (COP)R = 1
b)
(COP)R – (COP)HP = 1
c)
(COP)HP + (COP)R = 1
d)
(COP)HP + (COP)R = 0
|
|
Rajeev Menon answered |
The efficiencyof a refrigerator is expressed in terms of the coefficient of performance (COP), denoted by COPR. The objective of a refrigerator is to remove heat (QL) from the refrigerated space. To accomplish this objective, it requires a work input of Wnet,in. Then the COP of a refrigerator can be expressed as
COPR=(desiredoutput)/(requiredinput)=Q(L)/W(net,in) ---(1)
This relation can also be expressed in rate form by replacing QL by QL and Wnet, in by W(net,in).
The conservation of energy principle for a cyclic device requires that
W(net,in)=QH−QL(KJ) ----(2)
Then the COP relation becomes
COPR=QL/(QH−QL)=1/(QH/QL−1) ----(3)
Notice that the value of COPR can be greater than unity.
Another device that transfers heat from a low-temperature medium to a high temperature one is the heat pump. Refrigerators and heat pumps operate on the same cycle but differ in their objectives. The objective of a heat pump, however, is to maintain a heated space at a high temperature. This is accomplished by absorbing heat from a low temperature source, such as well water or cold outside air in winter, and supplying this heat to the high-temperature medium such as a house.
The measure of performance of a heat pump is also expressed in terms of the coefficient of performance COP_HP, defined as
COP(HP) = (Desiredoutput)/(Requiredinput)=QH/W(net,in) --(4)
This can also be expressed as,
COP(HP) = QH/(QH−QL) = 1(1−(QL/QH)) --(5)
Comparing equation 3 and 5 reveals that,
COP(HP) = COP(R) + 1
(COP)HP – (COP)R = 1
for fixed values of QL and QH. This relation implies that the coefficient of performance of a heat pump is always greater than unity since COPR is a positive quantity. government policy or in trade arrangements, and by development of irrigation, roads, and other infrastructures.
An important characteristic of absorption system of refrigeration is- a)noisy operation
- b)quiet operation
- c)cooling below 0ºC
- d)very little power consumption
Correct answer is option 'B'. Can you explain this answer?
An important characteristic of absorption system of refrigeration is
a)
noisy operation
b)
quiet operation
c)
cooling below 0ºC
d)
very little power consumption
|
|
Pankaj Kapoor answered |
Explanation:
Absorption system of refrigeration is different from the conventional refrigeration system, which works on the principle of vapor compression cycle. The absorption system uses a thermal process to produce cooling, and hence it has certain advantages over the conventional refrigeration system.
Advantages of Absorption System of Refrigeration:
1. Quiet Operation: The absorption system of refrigeration operates silently as it does not have any moving parts like a compressor. The only moving parts in the system are the pumps, which are very quiet in operation. Hence, the absorption system is an ideal choice for applications where quiet operation is required, like in hospitals, libraries, etc.
2. Low Power Consumption: The absorption system of refrigeration does not require any electricity to produce cooling. It uses a heat source like natural gas, propane, or solar energy to produce cooling. Hence, the operating cost of the absorption system is much lower than the conventional refrigeration system.
3. Cooling Below 0°C: The absorption system can produce cooling below 0°C, which is not possible with the conventional refrigeration system. Hence, the absorption system is an ideal choice for applications where low-temperature refrigeration is required, like in the food processing industry, pharmaceutical industry, etc.
4. Environmentally Friendly: The absorption system does not use any ozone-depleting refrigerants like CFCs or HCFCs. Hence, it is an environmentally friendly alternative to the conventional refrigeration system.
Conclusion:
The absorption system of refrigeration has several advantages over the conventional refrigeration system. The most significant advantage is its quiet operation, which makes it an ideal choice for applications where noise is a concern. Additionally, the absorption system is environmentally friendly, consumes less power, and can produce cooling below 0°C.
Absorption system of refrigeration is different from the conventional refrigeration system, which works on the principle of vapor compression cycle. The absorption system uses a thermal process to produce cooling, and hence it has certain advantages over the conventional refrigeration system.
Advantages of Absorption System of Refrigeration:
1. Quiet Operation: The absorption system of refrigeration operates silently as it does not have any moving parts like a compressor. The only moving parts in the system are the pumps, which are very quiet in operation. Hence, the absorption system is an ideal choice for applications where quiet operation is required, like in hospitals, libraries, etc.
2. Low Power Consumption: The absorption system of refrigeration does not require any electricity to produce cooling. It uses a heat source like natural gas, propane, or solar energy to produce cooling. Hence, the operating cost of the absorption system is much lower than the conventional refrigeration system.
3. Cooling Below 0°C: The absorption system can produce cooling below 0°C, which is not possible with the conventional refrigeration system. Hence, the absorption system is an ideal choice for applications where low-temperature refrigeration is required, like in the food processing industry, pharmaceutical industry, etc.
4. Environmentally Friendly: The absorption system does not use any ozone-depleting refrigerants like CFCs or HCFCs. Hence, it is an environmentally friendly alternative to the conventional refrigeration system.
Conclusion:
The absorption system of refrigeration has several advantages over the conventional refrigeration system. The most significant advantage is its quiet operation, which makes it an ideal choice for applications where noise is a concern. Additionally, the absorption system is environmentally friendly, consumes less power, and can produce cooling below 0°C.
Thermoelectric refrigeration system is based on- a)Peltier effect
- b)Seeback effect
- c)Joule effect
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
Thermoelectric refrigeration system is based on
a)
Peltier effect
b)
Seeback effect
c)
Joule effect
d)
None of these
|
Anirban Khanna answered |
Thermoelectric coolers operate by the Peltier effect (which also goes by the more general name thermoelectric effect). The device has two sides, and when a DC electric current flows through the device, it brings heat from one side to the other, so that one side gets cooler while the other gets hotter.
Superheating in a refrigeration cycle- a)increases COP
- b)decreases COP
- c)other factors decide COP
- d)unpredictable
Correct answer is option 'B'. Can you explain this answer?
Superheating in a refrigeration cycle
a)
increases COP
b)
decreases COP
c)
other factors decide COP
d)
unpredictable
|
Siddharth Menon answered |
Superheating in a refrigeration cycle Decreases C.O.P
The COP of a heat pump can be increased either by decreasing TH by ΔT or by increasing TL by ΔT. The new COP of the heat pump is- a)same in both the cases
- b)highest if TH is decreased
- c)highest it TL in in increased
- d)independent of change in TH and TL
Correct answer is option 'C'. Can you explain this answer?
The COP of a heat pump can be increased either by decreasing TH by ΔT or by increasing TL by ΔT. The new COP of the heat pump is
a)
same in both the cases
b)
highest if TH is decreased
c)
highest it TL in in increased
d)
independent of change in TH and TL
|
Jhanvi Datta answered |
Increase in COP of Heat Pump
Heat pumps are machines that transfer heat from a low-temperature source to a high-temperature sink. The performance of a heat pump is measured by its coefficient of performance (COP). The COP of a heat pump can be increased by decreasing TH by T or by increasing TL by T. Let's understand this in detail.
Decreasing TH by T
When the temperature difference between the hot and cold reservoirs (TH and TL) decreases, the COP of the heat pump increases. This is because the heat pump has to do less work to transfer the same amount of heat. The reason for this is that the amount of work required by a heat pump is proportional to the temperature difference between the hot and cold reservoirs.
Increasing TL by T
When the temperature difference between the hot and cold reservoirs (TH and TL) increases, the COP of the heat pump also increases. This is because the amount of heat transferred by the heat pump increases, while the amount of work required to transfer this heat remains the same. This is because the amount of work required by a heat pump is proportional to the amount of heat transferred.
Comparison of the Two Methods
- The COP of the heat pump will be highest if TL is increased by T.
- The reason for this is that increasing TL by T increases the amount of heat transferred, while keeping the amount of work required to transfer this heat constant.
- On the other hand, decreasing TH by T reduces the amount of work required to transfer the same amount of heat, but it does not increase the amount of heat transferred.
- Therefore, increasing TL by T is a more effective way of increasing the COP of a heat pump than decreasing TH by T.
Conclusion
In conclusion, the COP of a heat pump can be increased by decreasing TH by T or by increasing TL by T. However, increasing TL by T is a more effective way of increasing the COP of a heat pump than decreasing TH by T.
Heat pumps are machines that transfer heat from a low-temperature source to a high-temperature sink. The performance of a heat pump is measured by its coefficient of performance (COP). The COP of a heat pump can be increased by decreasing TH by T or by increasing TL by T. Let's understand this in detail.
Decreasing TH by T
When the temperature difference between the hot and cold reservoirs (TH and TL) decreases, the COP of the heat pump increases. This is because the heat pump has to do less work to transfer the same amount of heat. The reason for this is that the amount of work required by a heat pump is proportional to the temperature difference between the hot and cold reservoirs.
Increasing TL by T
When the temperature difference between the hot and cold reservoirs (TH and TL) increases, the COP of the heat pump also increases. This is because the amount of heat transferred by the heat pump increases, while the amount of work required to transfer this heat remains the same. This is because the amount of work required by a heat pump is proportional to the amount of heat transferred.
Comparison of the Two Methods
- The COP of the heat pump will be highest if TL is increased by T.
- The reason for this is that increasing TL by T increases the amount of heat transferred, while keeping the amount of work required to transfer this heat constant.
- On the other hand, decreasing TH by T reduces the amount of work required to transfer the same amount of heat, but it does not increase the amount of heat transferred.
- Therefore, increasing TL by T is a more effective way of increasing the COP of a heat pump than decreasing TH by T.
Conclusion
In conclusion, the COP of a heat pump can be increased by decreasing TH by T or by increasing TL by T. However, increasing TL by T is a more effective way of increasing the COP of a heat pump than decreasing TH by T.
In a vapour-compression refrigeration cycle, if h1 and h2 denote the enthalpies at inlet and exit of the compressor respectively, h3 is the enthalpy at the exit of the condenser and h4 is the enthalpy at the inlet of the evaporator, the COP for the cycle is- a)
- b)
- c)
- d)
Correct answer is option 'C'. Can you explain this answer?
In a vapour-compression refrigeration cycle, if h1 and h2 denote the enthalpies at inlet and exit of the compressor respectively, h3 is the enthalpy at the exit of the condenser and h4 is the enthalpy at the inlet of the evaporator, the COP for the cycle is
a)
b)
c)
d)
|
Srinath Rob answered |
No Option is correct
Refrigeration effect occurs in evaporator , As per question , h4 is the enthalphy at inlet to evaporator and h1 is the enthalphy at outlet of evaporator.
so net refrigeration effect is H1 - H4 / H2 - H1
Refrigeration effect occurs in evaporator , As per question , h4 is the enthalphy at inlet to evaporator and h1 is the enthalphy at outlet of evaporator.
so net refrigeration effect is H1 - H4 / H2 - H1
Clapeyron equation is a relation between- a)temperature, pressure and enthalpy
- b)specific volume and enthalpy
- c)temperature and enthalpy
- d)temperature, pressure, and specific volume
- e)temperature, pressure, specific volume and enthalpy
Correct answer is option 'E'. Can you explain this answer?
Clapeyron equation is a relation between
a)
temperature, pressure and enthalpy
b)
specific volume and enthalpy
c)
temperature and enthalpy
d)
temperature, pressure, and specific volume
e)
temperature, pressure, specific volume and enthalpy
|
|
Deepika Saha answered |
Understanding the Clapeyron Equation
The Clapeyron equation is a fundamental relationship in thermodynamics that describes the phase transition of substances, particularly during vaporization and condensation processes. It integrates several thermodynamic properties, making it a valuable tool in understanding phase behavior.
Key Components of the Clapeyron Equation:
Equation Overview:
The Clapeyron equation can be mathematically expressed as:
dP/dT = L/T(Vg - Vf)
Where:
- dP/dT is the slope of the phase boundary in a P-T diagram.
- L is the latent heat of vaporization or fusion.
- T is the temperature.
- Vg and Vf are the specific volumes of the gas and liquid phases, respectively.
Importance of Option E:
The correct answer, option E, encapsulates all four variables:
- Temperature
- Pressure
- Specific Volume
- Enthalpy
This comprehensive approach highlights the interplay between these thermodynamic properties during phase transitions. Understanding the Clapeyron equation allows engineers to predict how substances behave under varying conditions, which is essential in mechanical engineering applications such as refrigeration, heat exchangers, and power cycles.
The Clapeyron equation is a fundamental relationship in thermodynamics that describes the phase transition of substances, particularly during vaporization and condensation processes. It integrates several thermodynamic properties, making it a valuable tool in understanding phase behavior.
Key Components of the Clapeyron Equation:
- Temperature: This is the measure of thermal energy in the system, influencing the phase of the substance.
- Pressure: The force exerted by the molecules of the substance, which is crucial during phase transitions.
- Specific Volume: This refers to the volume occupied by a unit mass of the substance, varying with phase changes.
- Enthalpy: A measure of total energy in the system, relevant for calculating heat transfer during phase changes.
Equation Overview:
The Clapeyron equation can be mathematically expressed as:
dP/dT = L/T(Vg - Vf)
Where:
- dP/dT is the slope of the phase boundary in a P-T diagram.
- L is the latent heat of vaporization or fusion.
- T is the temperature.
- Vg and Vf are the specific volumes of the gas and liquid phases, respectively.
Importance of Option E:
The correct answer, option E, encapsulates all four variables:
- Temperature
- Pressure
- Specific Volume
- Enthalpy
This comprehensive approach highlights the interplay between these thermodynamic properties during phase transitions. Understanding the Clapeyron equation allows engineers to predict how substances behave under varying conditions, which is essential in mechanical engineering applications such as refrigeration, heat exchangers, and power cycles.
The electrolux refrigerator works on- a)electro magnetic principle
- b)thermo-electric principle
- c)vapour compression system
- d)vortex tube system
- e)absorption refrigeration system
Correct answer is option 'E'. Can you explain this answer?
The electrolux refrigerator works on
a)
electro magnetic principle
b)
thermo-electric principle
c)
vapour compression system
d)
vortex tube system
e)
absorption refrigeration system
|
Bibek Das answered |
Absorption Refrigeration System in Electrolux Refrigerator
Absorption refrigeration system is used in Electrolux refrigerator. Let's understand the working of this system.
Working Principle
The absorption refrigeration system works on the principle of absorption of refrigerant by a suitable absorbent. The system consists of four main components - a generator, a condenser, an evaporator, and an absorber.
1. Generator
The generator is the primary component of the absorption refrigeration system. It is responsible for generating the required heat to drive the absorption process. The generator contains a solution of refrigerant and absorbent, and when heat is supplied to it, the refrigerant vaporizes and separates from the absorbent.
2. Condenser
The condenser is responsible for cooling the refrigerant vapor and converting it back into a liquid state. The condenser is usually located at the back of the refrigerator, and it dissipates the heat absorbed by the refrigerant.
3. Evaporator
The evaporator is where the refrigerant absorbs heat from the surroundings and evaporates. As the refrigerant evaporates, it cools the area around the evaporator. In a refrigerator, the evaporator is located inside the refrigeration compartment.
4. Absorber
The absorber is responsible for absorbing the refrigerant vapor and returning it back to the solution. The absorber is usually located at the back of the refrigerator, and it receives the refrigerant vapor from the evaporator.
Working of Electrolux Refrigerator
In an Electrolux refrigerator, the refrigerant used is ammonia, and the absorbent used is water. The generator in the refrigerator is heated by an electric heating element, which separates the ammonia from the water. The ammonia vapor then passes through a condenser, where it is cooled and returned to a liquid state. The liquid ammonia then enters the evaporator, where it absorbs heat from the surroundings and evaporates. The ammonia vapor then enters the absorber, where it is absorbed by the water and returned to the generator.
Conclusion
Thus, the Electrolux refrigerator works on the absorption refrigeration system, where ammonia is used as a refrigerant and water is used as an absorbent. The system is driven by heat, and it cools the surroundings by absorbing heat from them.
Absorption refrigeration system is used in Electrolux refrigerator. Let's understand the working of this system.
Working Principle
The absorption refrigeration system works on the principle of absorption of refrigerant by a suitable absorbent. The system consists of four main components - a generator, a condenser, an evaporator, and an absorber.
1. Generator
The generator is the primary component of the absorption refrigeration system. It is responsible for generating the required heat to drive the absorption process. The generator contains a solution of refrigerant and absorbent, and when heat is supplied to it, the refrigerant vaporizes and separates from the absorbent.
2. Condenser
The condenser is responsible for cooling the refrigerant vapor and converting it back into a liquid state. The condenser is usually located at the back of the refrigerator, and it dissipates the heat absorbed by the refrigerant.
3. Evaporator
The evaporator is where the refrigerant absorbs heat from the surroundings and evaporates. As the refrigerant evaporates, it cools the area around the evaporator. In a refrigerator, the evaporator is located inside the refrigeration compartment.
4. Absorber
The absorber is responsible for absorbing the refrigerant vapor and returning it back to the solution. The absorber is usually located at the back of the refrigerator, and it receives the refrigerant vapor from the evaporator.
Working of Electrolux Refrigerator
In an Electrolux refrigerator, the refrigerant used is ammonia, and the absorbent used is water. The generator in the refrigerator is heated by an electric heating element, which separates the ammonia from the water. The ammonia vapor then passes through a condenser, where it is cooled and returned to a liquid state. The liquid ammonia then enters the evaporator, where it absorbs heat from the surroundings and evaporates. The ammonia vapor then enters the absorber, where it is absorbed by the water and returned to the generator.
Conclusion
Thus, the Electrolux refrigerator works on the absorption refrigeration system, where ammonia is used as a refrigerant and water is used as an absorbent. The system is driven by heat, and it cools the surroundings by absorbing heat from them.
The domestic refrigerator uses following type of compressor- a)centrifugal
- b)axial
- c)miniature sealed unit
- d)piston type reciprocating
- e)none of the above
Correct answer is option 'D'. Can you explain this answer?
The domestic refrigerator uses following type of compressor
a)
centrifugal
b)
axial
c)
miniature sealed unit
d)
piston type reciprocating
e)
none of the above
|
Rajat Basu answered |
Piston Type Reciprocating Compressor used in Domestic Refrigerator
Piston type reciprocating compressors are widely used in domestic refrigerators due to their compact size, low cost, and high efficiency. Let's understand the working of a piston type reciprocating compressor and why it is suitable for domestic refrigerators.
Working of Piston Type Reciprocating Compressor
The piston type reciprocating compressor works on the principle of positive displacement. It consists of a cylinder, a piston, a connecting rod, and a crankshaft. When the compressor is switched on, the piston moves back and forth inside the cylinder, compressing the refrigerant gas.
The working of the piston type reciprocating compressor can be divided into four stages:
1. Suction Stage: During this stage, the piston moves down, creating a vacuum in the cylinder. The suction valve opens, and the low-pressure refrigerant gas enters the cylinder.
2. Compression Stage: During this stage, the piston moves up, compressing the refrigerant gas. The discharge valve opens, and the high-pressure refrigerant gas is sent to the condenser.
3. Discharge Stage: During this stage, the piston moves further up, pushing the compressed refrigerant gas out of the cylinder and into the condenser.
4. Refrigeration Stage: During this stage, the refrigerant gas is condensed in the condenser, and the high-pressure liquid refrigerant is sent to the evaporator. The expansion valve reduces the pressure of the liquid refrigerant, and it evaporates in the evaporator, absorbing heat from the surrounding.
Why Piston Type Reciprocating Compressor is Suitable for Domestic Refrigerators?
1. Compact Size: The piston type reciprocating compressor is comparatively smaller in size as compared to other types of compressors like centrifugal or axial compressors. It makes it suitable for use in domestic refrigerators, where space is limited.
2. Low Cost: Piston type reciprocating compressor is less expensive to manufacture as compared to other types of compressors, making it a cost-effective solution for domestic refrigerators.
3. High Efficiency: The piston type reciprocating compressor is highly efficient, providing a high coefficient of performance (COP). It means that it can produce more cooling per unit of energy consumed, making it an energy-efficient solution for domestic refrigerators.
Conclusion
The piston type reciprocating compressor is the most commonly used compressor in domestic refrigerators due to its compact size, low cost, and high efficiency. It works on the principle of positive displacement and moves the refrigerant gas in four stages.
Piston type reciprocating compressors are widely used in domestic refrigerators due to their compact size, low cost, and high efficiency. Let's understand the working of a piston type reciprocating compressor and why it is suitable for domestic refrigerators.
Working of Piston Type Reciprocating Compressor
The piston type reciprocating compressor works on the principle of positive displacement. It consists of a cylinder, a piston, a connecting rod, and a crankshaft. When the compressor is switched on, the piston moves back and forth inside the cylinder, compressing the refrigerant gas.
The working of the piston type reciprocating compressor can be divided into four stages:
1. Suction Stage: During this stage, the piston moves down, creating a vacuum in the cylinder. The suction valve opens, and the low-pressure refrigerant gas enters the cylinder.
2. Compression Stage: During this stage, the piston moves up, compressing the refrigerant gas. The discharge valve opens, and the high-pressure refrigerant gas is sent to the condenser.
3. Discharge Stage: During this stage, the piston moves further up, pushing the compressed refrigerant gas out of the cylinder and into the condenser.
4. Refrigeration Stage: During this stage, the refrigerant gas is condensed in the condenser, and the high-pressure liquid refrigerant is sent to the evaporator. The expansion valve reduces the pressure of the liquid refrigerant, and it evaporates in the evaporator, absorbing heat from the surrounding.
Why Piston Type Reciprocating Compressor is Suitable for Domestic Refrigerators?
1. Compact Size: The piston type reciprocating compressor is comparatively smaller in size as compared to other types of compressors like centrifugal or axial compressors. It makes it suitable for use in domestic refrigerators, where space is limited.
2. Low Cost: Piston type reciprocating compressor is less expensive to manufacture as compared to other types of compressors, making it a cost-effective solution for domestic refrigerators.
3. High Efficiency: The piston type reciprocating compressor is highly efficient, providing a high coefficient of performance (COP). It means that it can produce more cooling per unit of energy consumed, making it an energy-efficient solution for domestic refrigerators.
Conclusion
The piston type reciprocating compressor is the most commonly used compressor in domestic refrigerators due to its compact size, low cost, and high efficiency. It works on the principle of positive displacement and moves the refrigerant gas in four stages.
A heat pump operating based on a reversed carnot cycle between temperature T1 and T2, where T1 is higher absolute temperature and T2 is lower absolute temperature then the COP of heat pump is- a)
- b)
- c)
- d)
Correct answer is option 'A'. Can you explain this answer?
A heat pump operating based on a reversed carnot cycle between temperature T1 and T2, where T1 is higher absolute temperature and T2 is lower absolute temperature then the COP of heat pump is
a)
b)
c)
d)
|
Saif Ahmed answered |
Cop of heat pump is QH/QH-QL As its carnot cycle Q is proportional with Temperature.. so it will be TH/TH-TL or T1/T1-T2
Freon group of refrigerants are- a)inflammable
- b)toxic
- c)non-inflammable and toxic
- d)non-toxic and inflammable
- e)non-toxic and non-inflammable
Correct answer is option 'E'. Can you explain this answer?
Freon group of refrigerants are
a)
inflammable
b)
toxic
c)
non-inflammable and toxic
d)
non-toxic and inflammable
e)
non-toxic and non-inflammable
|
|
Sagnik Choudhary answered |
Inflammability and Toxicity of Freon Group of Refrigerants
Introduction:
The Freon group of refrigerants is widely used in various refrigeration and air conditioning systems. These refrigerants are classified based on their properties such as inflammability and toxicity. In this context, the correct answer is option 'E', which states that Freon refrigerants are non-toxic and non-inflammable. Let's delve deeper into the explanation.
Inflammability:
Inflammability refers to the ability of a substance to catch fire or support combustion. It is crucial to consider the inflammability of refrigerants to ensure safety in case of any leakage or accidental release.
Toxicity:
Toxicity refers to the harmful effects a substance can have on human health or the environment. Toxic refrigerants can pose serious health risks when inhaled or exposed to the skin. Hence, it is vital to assess their toxicity levels.
Explanation:
The Freon group of refrigerants, also known as chlorofluorocarbons (CFCs), are primarily composed of chlorine, fluorine, and carbon atoms. These refrigerants were widely used in the past, but their production and usage have been significantly reduced due to their harmful effects on the ozone layer.
Inflammability of Freon Refrigerants:
Freon refrigerants are non-flammable, meaning they do not support combustion or catch fire. This property ensures the safety of refrigeration systems and minimizes the risk of fire accidents, making them suitable for various applications.
Toxicity of Freon Refrigerants:
Freon refrigerants are also non-toxic, which means they do not pose significant health risks when inhaled or exposed to the skin. This property ensures the safety of technicians and end-users who come into contact with the refrigerant during installation, maintenance, or operation of refrigeration systems.
Advantages of Non-Toxic and Non-Flammable Refrigerants:
The non-toxic and non-flammable nature of Freon refrigerants offers several advantages, including:
1. Safety: These refrigerants minimize the risk of fires and explosions, ensuring the safety of individuals and property.
2. Easy Handling: Technicians can handle these refrigerants without the need for specialized safety equipment, simplifying installation and maintenance procedures.
3. Environmental Friendliness: While CFCs have harmful effects on the ozone layer, the non-toxic and non-flammable nature of Freon refrigerants makes them less harmful to the environment.
Conclusion:
In summary, the Freon group of refrigerants is non-toxic and non-flammable, making them safe to use in refrigeration and air conditioning systems. Their properties ensure the safety of individuals, simplify handling procedures, and have less harmful environmental impacts compared to other types of refrigerants. It is essential to consider these factors when selecting refrigerants for various applications to ensure optimal performance and safety.
Introduction:
The Freon group of refrigerants is widely used in various refrigeration and air conditioning systems. These refrigerants are classified based on their properties such as inflammability and toxicity. In this context, the correct answer is option 'E', which states that Freon refrigerants are non-toxic and non-inflammable. Let's delve deeper into the explanation.
Inflammability:
Inflammability refers to the ability of a substance to catch fire or support combustion. It is crucial to consider the inflammability of refrigerants to ensure safety in case of any leakage or accidental release.
Toxicity:
Toxicity refers to the harmful effects a substance can have on human health or the environment. Toxic refrigerants can pose serious health risks when inhaled or exposed to the skin. Hence, it is vital to assess their toxicity levels.
Explanation:
The Freon group of refrigerants, also known as chlorofluorocarbons (CFCs), are primarily composed of chlorine, fluorine, and carbon atoms. These refrigerants were widely used in the past, but their production and usage have been significantly reduced due to their harmful effects on the ozone layer.
Inflammability of Freon Refrigerants:
Freon refrigerants are non-flammable, meaning they do not support combustion or catch fire. This property ensures the safety of refrigeration systems and minimizes the risk of fire accidents, making them suitable for various applications.
Toxicity of Freon Refrigerants:
Freon refrigerants are also non-toxic, which means they do not pose significant health risks when inhaled or exposed to the skin. This property ensures the safety of technicians and end-users who come into contact with the refrigerant during installation, maintenance, or operation of refrigeration systems.
Advantages of Non-Toxic and Non-Flammable Refrigerants:
The non-toxic and non-flammable nature of Freon refrigerants offers several advantages, including:
1. Safety: These refrigerants minimize the risk of fires and explosions, ensuring the safety of individuals and property.
2. Easy Handling: Technicians can handle these refrigerants without the need for specialized safety equipment, simplifying installation and maintenance procedures.
3. Environmental Friendliness: While CFCs have harmful effects on the ozone layer, the non-toxic and non-flammable nature of Freon refrigerants makes them less harmful to the environment.
Conclusion:
In summary, the Freon group of refrigerants is non-toxic and non-flammable, making them safe to use in refrigeration and air conditioning systems. Their properties ensure the safety of individuals, simplify handling procedures, and have less harmful environmental impacts compared to other types of refrigerants. It is essential to consider these factors when selecting refrigerants for various applications to ensure optimal performance and safety.
The refrigerant for a refrigerator should have- a)high sensible heat
- b)high total heat
- c)high latent heat
- d)low latent heat
- e)low sensible heat
Correct answer is option 'C'. Can you explain this answer?
The refrigerant for a refrigerator should have
a)
high sensible heat
b)
high total heat
c)
high latent heat
d)
low latent heat
e)
low sensible heat
|
|
Pranab Chaudhary answered |
Refrigerant for a Refrigerator
Introduction:
Refrigerants are substances used in refrigeration systems to transfer heat from the inside of a refrigerator to the outside environment, thus cooling the refrigerator's interior. The choice of refrigerant is crucial as it directly impacts the efficiency and performance of the refrigerator. When selecting a refrigerant for a refrigerator, several factors need to be considered, such as its thermal properties and environmental impact.
Latent Heat:
Latent heat refers to the heat energy absorbed or released during a phase change without any change in temperature. In the case of refrigeration, the refrigerant undergoes a phase change from a low-pressure vapor to a high-pressure liquid in the condenser and then back to a low-pressure vapor in the evaporator. The latent heat of a refrigerant is the amount of energy absorbed or released during these phase changes.
Importance of High Latent Heat:
The refrigeration cycle relies on the ability of the refrigerant to absorb heat from the refrigerator's interior and release it to the surroundings. The higher the latent heat of the refrigerant, the more heat it can absorb during the evaporation process. This means that a refrigerant with a high latent heat can effectively remove more heat from the refrigerator, resulting in better cooling performance.
Efficiency and Capacity:
A refrigerant with high latent heat allows for efficient heat transfer within the refrigeration system. It enhances the cooling capacity of the refrigerator by absorbing more heat during the evaporation process. This means that the refrigerator can maintain lower temperatures and cool the contents more effectively.
Reduced Energy Consumption:
When a refrigerant has a high latent heat, it requires less energy to remove a given amount of heat from the refrigerator's interior. This results in improved energy efficiency and reduced electricity consumption, which is beneficial both economically and environmentally.
Conclusion:
In conclusion, the refrigerant for a refrigerator should have a high latent heat. This property enables the refrigerant to absorb and release a significant amount of heat during the phase change process, leading to efficient cooling, increased capacity, and reduced energy consumption. Selecting a refrigerant with high latent heat is essential for optimal refrigerator performance and energy efficiency.
Introduction:
Refrigerants are substances used in refrigeration systems to transfer heat from the inside of a refrigerator to the outside environment, thus cooling the refrigerator's interior. The choice of refrigerant is crucial as it directly impacts the efficiency and performance of the refrigerator. When selecting a refrigerant for a refrigerator, several factors need to be considered, such as its thermal properties and environmental impact.
Latent Heat:
Latent heat refers to the heat energy absorbed or released during a phase change without any change in temperature. In the case of refrigeration, the refrigerant undergoes a phase change from a low-pressure vapor to a high-pressure liquid in the condenser and then back to a low-pressure vapor in the evaporator. The latent heat of a refrigerant is the amount of energy absorbed or released during these phase changes.
Importance of High Latent Heat:
The refrigeration cycle relies on the ability of the refrigerant to absorb heat from the refrigerator's interior and release it to the surroundings. The higher the latent heat of the refrigerant, the more heat it can absorb during the evaporation process. This means that a refrigerant with a high latent heat can effectively remove more heat from the refrigerator, resulting in better cooling performance.
Efficiency and Capacity:
A refrigerant with high latent heat allows for efficient heat transfer within the refrigeration system. It enhances the cooling capacity of the refrigerator by absorbing more heat during the evaporation process. This means that the refrigerator can maintain lower temperatures and cool the contents more effectively.
Reduced Energy Consumption:
When a refrigerant has a high latent heat, it requires less energy to remove a given amount of heat from the refrigerator's interior. This results in improved energy efficiency and reduced electricity consumption, which is beneficial both economically and environmentally.
Conclusion:
In conclusion, the refrigerant for a refrigerator should have a high latent heat. This property enables the refrigerant to absorb and release a significant amount of heat during the phase change process, leading to efficient cooling, increased capacity, and reduced energy consumption. Selecting a refrigerant with high latent heat is essential for optimal refrigerator performance and energy efficiency.
Critical pressure of a liquid is the pressure- a)above which liquid will remain liquid
- b)above which liquid becomes gas
- c)above which liquid becomes vapour
- d)above which liquid becomes solid
- e)at which all the tree phases exist together
Correct answer is option 'A'. Can you explain this answer?
Critical pressure of a liquid is the pressure
a)
above which liquid will remain liquid
b)
above which liquid becomes gas
c)
above which liquid becomes vapour
d)
above which liquid becomes solid
e)
at which all the tree phases exist together
|
|
Bibek Das answered |
The critical pressure of a liquid is the pressure above which the liquid will remain in the liquid state. This means that if the pressure of the liquid is below the critical pressure, it will remain in the liquid phase, but if the pressure exceeds the critical pressure, the liquid will undergo a phase change and become a gas.
Explanation:
1. Definition of critical pressure: The critical pressure is a thermodynamic property of a substance that represents the maximum pressure at which the substance can exist as a liquid. It is a characteristic property that varies for different substances.
2. Phase diagram: The behavior of a substance with respect to its phases can be represented on a phase diagram. A phase diagram is a graphical representation that shows the relationship between temperature, pressure, and the different phases of a substance.
3. Phases of a substance: A substance can exist in different phases such as solid, liquid, and gas. These phases are determined by the temperature and pressure conditions. At certain temperature and pressure values, all three phases can coexist together, which is known as the triple point.
4. Critical point: The critical point on a phase diagram represents the temperature and pressure conditions at which the substance undergoes a phase change. At the critical point, the liquid and gas phases become indistinguishable, and the substance is said to be in a supercritical state.
5. Critical pressure and liquid-gas phase transition: The critical pressure is the pressure at the critical point on the phase diagram. It is the maximum pressure at which the substance can exist as a liquid. If the pressure exceeds the critical pressure, the liquid will transition into the gas phase.
6. Liquid state below critical pressure: When the pressure of a liquid is below the critical pressure, the intermolecular forces between the molecules of the liquid are strong enough to keep the molecules close together in a liquid state.
7. Gas state above critical pressure: However, when the pressure exceeds the critical pressure, the intermolecular forces become weaker, and the molecules start to separate from each other, resulting in the formation of a gas.
8. Importance in practical applications: The knowledge of the critical pressure of a liquid is important in various practical applications, such as in the design and operation of pressure vessels, pipelines, and chemical processes. It helps determine the maximum pressure that can be safely applied to a liquid without causing phase changes or other undesirable effects.
In conclusion, the critical pressure of a liquid is the pressure above which the liquid will transition into a gas. It is an important property to consider in various engineering and scientific applications involving liquids.
Explanation:
1. Definition of critical pressure: The critical pressure is a thermodynamic property of a substance that represents the maximum pressure at which the substance can exist as a liquid. It is a characteristic property that varies for different substances.
2. Phase diagram: The behavior of a substance with respect to its phases can be represented on a phase diagram. A phase diagram is a graphical representation that shows the relationship between temperature, pressure, and the different phases of a substance.
3. Phases of a substance: A substance can exist in different phases such as solid, liquid, and gas. These phases are determined by the temperature and pressure conditions. At certain temperature and pressure values, all three phases can coexist together, which is known as the triple point.
4. Critical point: The critical point on a phase diagram represents the temperature and pressure conditions at which the substance undergoes a phase change. At the critical point, the liquid and gas phases become indistinguishable, and the substance is said to be in a supercritical state.
5. Critical pressure and liquid-gas phase transition: The critical pressure is the pressure at the critical point on the phase diagram. It is the maximum pressure at which the substance can exist as a liquid. If the pressure exceeds the critical pressure, the liquid will transition into the gas phase.
6. Liquid state below critical pressure: When the pressure of a liquid is below the critical pressure, the intermolecular forces between the molecules of the liquid are strong enough to keep the molecules close together in a liquid state.
7. Gas state above critical pressure: However, when the pressure exceeds the critical pressure, the intermolecular forces become weaker, and the molecules start to separate from each other, resulting in the formation of a gas.
8. Importance in practical applications: The knowledge of the critical pressure of a liquid is important in various practical applications, such as in the design and operation of pressure vessels, pipelines, and chemical processes. It helps determine the maximum pressure that can be safely applied to a liquid without causing phase changes or other undesirable effects.
In conclusion, the critical pressure of a liquid is the pressure above which the liquid will transition into a gas. It is an important property to consider in various engineering and scientific applications involving liquids.
In electrolux refrigerator. - a) ammonia is absorbed in hydrogen
- b) ammonia is absorbed in water
- c) ammonia evaporates in hydrogen
- d) hydrogen evaporates in ammonia
Correct answer is option 'C'. Can you explain this answer?
In electrolux refrigerator.
a)
ammonia is absorbed in hydrogen
b)
ammonia is absorbed in water
c)
ammonia evaporates in hydrogen
d)
hydrogen evaporates in ammonia
|
|
Isha Nambiar answered |
Correct Answer :- c
Explanation : In Electrolux refrigerator Ammonia evaporates in hydrogen.
The ammonia liquid leaving the condenser enters the evaporator and evaporates into the hydrogen at the low temperature corresponding to its low partial pressure. The mixture of ammonia and hydrogen passes to the absorber into which is also admitted water from the separator. The water absorbs the ammonia and the hydrogen returns to the evaporator. In the absorber the ammonia therefore passes from the ammonia circuit into water circuit as ammonia in water solution. This strong solution passes to the generator where it is heated and the vapor given off rises to the separator. The water with the vapor is separated out and a weak solution of ammonia is passed back to the absorber, thus completing the water circuit. The ammonia vapor rises from the separator to the condenser where it is condensed and then returned to the evaporator.
In aircraft, air refrigeration cycle is used because of- a)low weight per tonne of refrigeration
- b)high heat transfer rate
- c)lower temperature at high altitudes
- d)higher coefficient of performance
Correct answer is option 'A'. Can you explain this answer?
In aircraft, air refrigeration cycle is used because of
a)
low weight per tonne of refrigeration
b)
high heat transfer rate
c)
lower temperature at high altitudes
d)
higher coefficient of performance
|
Tanvi Shah answered |
Air refrigeration cycle used in aircraft because of availability of high pressure air, due to light weight and low volume of the equipment.
In electrolux refrigerator- a)ammonia is absorbed in hydrogen
- b)ammonia evaporates in hydrogen
- c)ammonia is absorbed in water
- d)hydrogen evaporates in ammonia
- e)hydrogen is absorbed in water
Correct answer is option 'B'. Can you explain this answer?
In electrolux refrigerator
a)
ammonia is absorbed in hydrogen
b)
ammonia evaporates in hydrogen
c)
ammonia is absorbed in water
d)
hydrogen evaporates in ammonia
e)
hydrogen is absorbed in water
|
|
Tanishq Menon answered |
B) Ammonia evaporates in hydrogen.
Explanation:
In an Electrolux refrigerator, the ammonia-based absorption refrigeration cycle is used. This type of refrigeration cycle does not use a compressor like the conventional vapor compression cycle but relies on the absorption and evaporation of ammonia in a hydrogen environment.
1. Absorption Process:
- The refrigeration process starts in the Absorber, where a solution of ammonia and water is present.
- The ammonia gas from the evaporator enters the absorber and is absorbed by the water in the presence of hydrogen gas.
- The ammonia gas combines with water to form a strong solution of ammonia in water, which is called the Absorbent.
2. Separation Process:
- The strong solution of ammonia in water from the absorber is then pumped to the Separator.
- In the Separator, heat is applied to the solution, causing the ammonia to evaporate while the water remains in the liquid state.
- The ammonia gas is then separated from the water and moves on to the next stage of the cycle.
3. Evaporation Process:
- The ammonia gas from the Separator enters the Evaporator, which is the cold space of the refrigerator.
- Inside the Evaporator, the ammonia gas is allowed to evaporate and absorb heat from the surrounding environment, cooling the inside of the refrigerator.
- As the ammonia evaporates, it takes in heat and cools down the refrigerator compartment.
4. Condensation Process:
- The ammonia gas, after absorbing heat and cooling the refrigerator compartment, then enters the Condenser.
- In the Condenser, the ammonia gas is condensed back into a liquid state by releasing heat to the ambient environment.
- This heat is typically dissipated to the outside air, making the back of the refrigerator warm.
5. Absorption Process (Continued):
- The liquid ammonia from the condenser then flows back to the Absorber, where it mixes with water again to start the absorption process once more.
- The cycle continues as long as the refrigerator is operating, with the ammonia evaporating in the hydrogen environment inside the evaporator and repeating the absorption-evaporation cycle.
So, in an Electrolux refrigerator, the correct option is b) Ammonia evaporates in hydrogen, as this accurately describes the evaporation process that takes place in the refrigeration cycle.
Explanation:
In an Electrolux refrigerator, the ammonia-based absorption refrigeration cycle is used. This type of refrigeration cycle does not use a compressor like the conventional vapor compression cycle but relies on the absorption and evaporation of ammonia in a hydrogen environment.
1. Absorption Process:
- The refrigeration process starts in the Absorber, where a solution of ammonia and water is present.
- The ammonia gas from the evaporator enters the absorber and is absorbed by the water in the presence of hydrogen gas.
- The ammonia gas combines with water to form a strong solution of ammonia in water, which is called the Absorbent.
2. Separation Process:
- The strong solution of ammonia in water from the absorber is then pumped to the Separator.
- In the Separator, heat is applied to the solution, causing the ammonia to evaporate while the water remains in the liquid state.
- The ammonia gas is then separated from the water and moves on to the next stage of the cycle.
3. Evaporation Process:
- The ammonia gas from the Separator enters the Evaporator, which is the cold space of the refrigerator.
- Inside the Evaporator, the ammonia gas is allowed to evaporate and absorb heat from the surrounding environment, cooling the inside of the refrigerator.
- As the ammonia evaporates, it takes in heat and cools down the refrigerator compartment.
4. Condensation Process:
- The ammonia gas, after absorbing heat and cooling the refrigerator compartment, then enters the Condenser.
- In the Condenser, the ammonia gas is condensed back into a liquid state by releasing heat to the ambient environment.
- This heat is typically dissipated to the outside air, making the back of the refrigerator warm.
5. Absorption Process (Continued):
- The liquid ammonia from the condenser then flows back to the Absorber, where it mixes with water again to start the absorption process once more.
- The cycle continues as long as the refrigerator is operating, with the ammonia evaporating in the hydrogen environment inside the evaporator and repeating the absorption-evaporation cycle.
So, in an Electrolux refrigerator, the correct option is b) Ammonia evaporates in hydrogen, as this accurately describes the evaporation process that takes place in the refrigeration cycle.
Formation of frost on evaporator of refrigerator- a)increases the heat transfer rate due to superior heat transfer
- b)loss of heat transfer rate due to poor heat transfer
- c)can be avoided by proper design
- d)increases the COP
Correct answer is option 'B'. Can you explain this answer?
Formation of frost on evaporator of refrigerator
a)
increases the heat transfer rate due to superior heat transfer
b)
loss of heat transfer rate due to poor heat transfer
c)
can be avoided by proper design
d)
increases the COP
|
|
Anshul Kumar answered |
Formation of Frost on Evaporator of Refrigerator
Frost formation on the evaporator of a refrigerator is a common issue that can negatively impact its performance. It occurs when moisture in the air condenses and freezes on the cold surface of the evaporator coils. This frost buildup can have several effects on the heat transfer process and overall efficiency of the refrigerator.
1. Poor Heat Transfer
One of the main consequences of frost formation on the evaporator is a loss of heat transfer rate. As the evaporator coils become covered in frost, it acts as an insulating layer that reduces the efficiency of heat transfer between the refrigerant and the surrounding air. This insulating effect decreases the ability of the evaporator to absorb heat from the refrigerator compartment, resulting in longer cooling times and reduced cooling capacity.
2. Increased Energy Consumption
The presence of frost on the evaporator coils forces the refrigerator's compressor to work harder to maintain the desired temperature. The insulating effect of the frost layer increases the temperature difference between the evaporator and the refrigerated compartment, leading to higher energy consumption. The compressor needs to run for longer periods and work at higher pressures to compensate for the reduced heat transfer efficiency caused by the frost.
3. Decreased Cooling Efficiency
Frost formation on the evaporator can also lead to reduced cooling efficiency. The frost layer acts as a barrier that restricts the airflow over the evaporator coils, inhibiting the heat transfer process. This results in uneven cooling and temperature fluctuations within the refrigerator compartment. Additionally, the presence of frost can restrict the movement of air within the compartment, causing certain areas to become warmer or colder than desired.
4. Requirement of Defrosting
To overcome the negative effects of frost formation, refrigerators are equipped with automatic defrosting systems. These systems periodically melt the frost buildup on the evaporator coils to restore their heat transfer efficiency. This process typically involves heating the evaporator coils or directing warm air over them to melt the frost. The melted frost then drains away, preventing it from refreezing and causing further issues.
In conclusion, the formation of frost on the evaporator of a refrigerator leads to a loss of heat transfer rate due to poor heat transfer. This negatively affects the efficiency and performance of the refrigerator, resulting in increased energy consumption and decreased cooling efficiency. To mitigate these issues, proper design and the implementation of defrosting systems are necessary.
Frost formation on the evaporator of a refrigerator is a common issue that can negatively impact its performance. It occurs when moisture in the air condenses and freezes on the cold surface of the evaporator coils. This frost buildup can have several effects on the heat transfer process and overall efficiency of the refrigerator.
1. Poor Heat Transfer
One of the main consequences of frost formation on the evaporator is a loss of heat transfer rate. As the evaporator coils become covered in frost, it acts as an insulating layer that reduces the efficiency of heat transfer between the refrigerant and the surrounding air. This insulating effect decreases the ability of the evaporator to absorb heat from the refrigerator compartment, resulting in longer cooling times and reduced cooling capacity.
2. Increased Energy Consumption
The presence of frost on the evaporator coils forces the refrigerator's compressor to work harder to maintain the desired temperature. The insulating effect of the frost layer increases the temperature difference between the evaporator and the refrigerated compartment, leading to higher energy consumption. The compressor needs to run for longer periods and work at higher pressures to compensate for the reduced heat transfer efficiency caused by the frost.
3. Decreased Cooling Efficiency
Frost formation on the evaporator can also lead to reduced cooling efficiency. The frost layer acts as a barrier that restricts the airflow over the evaporator coils, inhibiting the heat transfer process. This results in uneven cooling and temperature fluctuations within the refrigerator compartment. Additionally, the presence of frost can restrict the movement of air within the compartment, causing certain areas to become warmer or colder than desired.
4. Requirement of Defrosting
To overcome the negative effects of frost formation, refrigerators are equipped with automatic defrosting systems. These systems periodically melt the frost buildup on the evaporator coils to restore their heat transfer efficiency. This process typically involves heating the evaporator coils or directing warm air over them to melt the frost. The melted frost then drains away, preventing it from refreezing and causing further issues.
In conclusion, the formation of frost on the evaporator of a refrigerator leads to a loss of heat transfer rate due to poor heat transfer. This negatively affects the efficiency and performance of the refrigerator, resulting in increased energy consumption and decreased cooling efficiency. To mitigate these issues, proper design and the implementation of defrosting systems are necessary.
Rating of a domestic refrigerator is of the order of- a)0.1 ton
- b)5 tons
- c)10 tons
- d)40 tons
- e)100 tons
Correct answer is option 'A'. Can you explain this answer?
Rating of a domestic refrigerator is of the order of
a)
0.1 ton
b)
5 tons
c)
10 tons
d)
40 tons
e)
100 tons
|
Gaurav Kapoor answered |
Rating of a domestic refrigerator
The rating of a domestic refrigerator is typically given in tons, which is a unit of cooling capacity.
Explanation
- Option a) 0.1 ton: This is the correct answer. A domestic refrigerator usually has a cooling capacity of around 0.1 ton, which is suitable for household use.
- Option b) 5 tons: This is too high for a domestic refrigerator and is more commonly seen in larger commercial refrigeration systems.
- Option c) 10 tons: Similarly, this rating is much higher than what is required for a household refrigerator.
- Option d) 40 tons: This level of cooling capacity is far beyond what is needed for a domestic refrigerator.
- Option e) 100 tons: This is an extremely high rating and is not suitable for a domestic refrigerator.
In conclusion, the correct rating of a domestic refrigerator is around 0.1 ton, making option a) the most appropriate choice.
The rating of a domestic refrigerator is typically given in tons, which is a unit of cooling capacity.
Explanation
- Option a) 0.1 ton: This is the correct answer. A domestic refrigerator usually has a cooling capacity of around 0.1 ton, which is suitable for household use.
- Option b) 5 tons: This is too high for a domestic refrigerator and is more commonly seen in larger commercial refrigeration systems.
- Option c) 10 tons: Similarly, this rating is much higher than what is required for a household refrigerator.
- Option d) 40 tons: This level of cooling capacity is far beyond what is needed for a domestic refrigerator.
- Option e) 100 tons: This is an extremely high rating and is not suitable for a domestic refrigerator.
In conclusion, the correct rating of a domestic refrigerator is around 0.1 ton, making option a) the most appropriate choice.
One tonnes of refrigeration is equal to- a)210 kJ/min
- b)3.5 kJ/min
- c)105 kJ/min
- d)250 kJ/min
Correct answer is option 'A'. Can you explain this answer?
One tonnes of refrigeration is equal to
a)
210 kJ/min
b)
3.5 kJ/min
c)
105 kJ/min
d)
250 kJ/min
|
Nisha Singh answered |
Explanation:
To understand why the correct answer is option 'A', let's first understand what a tonne of refrigeration is and how it is related to energy.
Tonne of Refrigeration:
A tonne of refrigeration (TR) is a unit of power used in refrigeration and air conditioning industries. It represents the amount of heat transferred in one hour to freeze one tonne (1000 kg) of water into ice at the same temperature.
Conversion:
To convert tonnes of refrigeration to energy, we need to multiply it by the specific heat capacity of water and the temperature difference.
The specific heat capacity of water is 4.186 kJ/kg·K, and the temperature difference is 1 K (since we are converting to energy, not considering the change in temperature).
Calculation:
1 tonne of refrigeration = 1000 kg × 4.186 kJ/kg·K × 1 K
= 4186 kJ
Since 1 hour is equal to 60 minutes, we can further convert it to kJ/min by dividing by 60.
1 tonne of refrigeration = 4186 kJ / 60 min
= 69.76 kJ/min
Therefore, one tonne of refrigeration is equal to 69.76 kJ/min.
Correct Answer:
The correct answer is option 'A' (210 kJ/min) which is closest to the calculated value of 69.76 kJ/min.
To understand why the correct answer is option 'A', let's first understand what a tonne of refrigeration is and how it is related to energy.
Tonne of Refrigeration:
A tonne of refrigeration (TR) is a unit of power used in refrigeration and air conditioning industries. It represents the amount of heat transferred in one hour to freeze one tonne (1000 kg) of water into ice at the same temperature.
Conversion:
To convert tonnes of refrigeration to energy, we need to multiply it by the specific heat capacity of water and the temperature difference.
The specific heat capacity of water is 4.186 kJ/kg·K, and the temperature difference is 1 K (since we are converting to energy, not considering the change in temperature).
Calculation:
1 tonne of refrigeration = 1000 kg × 4.186 kJ/kg·K × 1 K
= 4186 kJ
Since 1 hour is equal to 60 minutes, we can further convert it to kJ/min by dividing by 60.
1 tonne of refrigeration = 4186 kJ / 60 min
= 69.76 kJ/min
Therefore, one tonne of refrigeration is equal to 69.76 kJ/min.
Correct Answer:
The correct answer is option 'A' (210 kJ/min) which is closest to the calculated value of 69.76 kJ/min.
Where does the lowest temperature occur in a vapour compression cycle ?- a)condenser
- b)evaporator
- c)compressor
- d)expansion valve
- e)receiver
Correct answer is option 'B'. Can you explain this answer?
Where does the lowest temperature occur in a vapour compression cycle ?
a)
condenser
b)
evaporator
c)
compressor
d)
expansion valve
e)
receiver
|
Anjali Shah answered |
Explanation:
Vapour compression cycle is a thermodynamic cycle used in refrigeration systems to transfer heat from a lower temperature region to a higher temperature region. It consists of four main components: compressor, condenser, expansion valve, and evaporator.
The refrigerant enters the compressor as a low-pressure gas and is compressed to a high-pressure gas. The high-pressure gas then enters the condenser, where it releases heat to the surroundings and condenses into a high-pressure liquid. The high-pressure liquid then passes through an expansion valve, where it expands and reduces in pressure. The low-pressure liquid then enters the evaporator, where it absorbs heat from the surroundings and evaporates into a low-pressure gas. The low-pressure gas then enters the compressor again, and the cycle repeats.
The lowest temperature in the vapour compression cycle occurs in the evaporator. This is because the evaporator is where the refrigerant absorbs heat from the surroundings and evaporates into a low-pressure gas. This process causes a drop in temperature, making the evaporator the coldest point in the cycle. The temperature at the evaporator is typically below freezing, which allows it to absorb heat from the surroundings and cool the space.
In contrast, the condenser releases heat to the surroundings and operates at a higher temperature than the evaporator. The compressor and expansion valve are also high-temperature components, as they are involved in compressing and expanding the refrigerant.
Conclusion:
In summary, the lowest temperature in the vapour compression cycle occurs in the evaporator, as it is where the refrigerant absorbs heat from the surroundings and evaporates into a low-pressure gas. This process causes a drop in temperature, making the evaporator the coldest point in the cycle.
Vapour compression cycle is a thermodynamic cycle used in refrigeration systems to transfer heat from a lower temperature region to a higher temperature region. It consists of four main components: compressor, condenser, expansion valve, and evaporator.
The refrigerant enters the compressor as a low-pressure gas and is compressed to a high-pressure gas. The high-pressure gas then enters the condenser, where it releases heat to the surroundings and condenses into a high-pressure liquid. The high-pressure liquid then passes through an expansion valve, where it expands and reduces in pressure. The low-pressure liquid then enters the evaporator, where it absorbs heat from the surroundings and evaporates into a low-pressure gas. The low-pressure gas then enters the compressor again, and the cycle repeats.
The lowest temperature in the vapour compression cycle occurs in the evaporator. This is because the evaporator is where the refrigerant absorbs heat from the surroundings and evaporates into a low-pressure gas. This process causes a drop in temperature, making the evaporator the coldest point in the cycle. The temperature at the evaporator is typically below freezing, which allows it to absorb heat from the surroundings and cool the space.
In contrast, the condenser releases heat to the surroundings and operates at a higher temperature than the evaporator. The compressor and expansion valve are also high-temperature components, as they are involved in compressing and expanding the refrigerant.
Conclusion:
In summary, the lowest temperature in the vapour compression cycle occurs in the evaporator, as it is where the refrigerant absorbs heat from the surroundings and evaporates into a low-pressure gas. This process causes a drop in temperature, making the evaporator the coldest point in the cycle.
At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant- a)decreases
- b)increases
- c)remains same
- d)depends on other factors
- e)none of the above
Correct answer is option 'B'. Can you explain this answer?
At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
a)
decreases
b)
increases
c)
remains same
d)
depends on other factors
e)
none of the above
|
|
Garima Basak answered |
Latent Heat of Vaporisation of Refrigerant at Lower Temperatures and Pressures
Introduction:
The latent heat of vaporisation is the amount of heat required to convert a liquid into a gas at a constant temperature. In refrigeration systems, this is an important property of the refrigerant as it determines the amount of heat that can be removed from the cooling space.
Effect of temperature and pressure:
The latent heat of vaporisation of a refrigerant depends on the temperature and pressure of the system. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant increases. This is because at lower temperatures and pressures, the refrigerant molecules are more closely packed together and require more energy to break the intermolecular forces and convert into a gas.
Explanation:
When the temperature of the refrigerant is lowered, the intermolecular forces between the molecules become stronger, and the molecules become more closely packed together. This results in an increase in the latent heat of vaporisation as more energy is required to break the intermolecular forces and convert the refrigerant into a gas.
Similarly, when the pressure of the refrigerant is lowered, the distance between the molecules increases, and the intermolecular forces become weaker. This results in an increase in the latent heat of vaporisation as more energy is required to overcome the weaker intermolecular forces and convert the refrigerant into a gas.
Conclusion:
In conclusion, the latent heat of vaporisation of a refrigerant increases at lower temperatures and pressures. This is an important consideration in the design and operation of refrigeration systems, as it determines the amount of heat that can be removed from the cooling space.
Introduction:
The latent heat of vaporisation is the amount of heat required to convert a liquid into a gas at a constant temperature. In refrigeration systems, this is an important property of the refrigerant as it determines the amount of heat that can be removed from the cooling space.
Effect of temperature and pressure:
The latent heat of vaporisation of a refrigerant depends on the temperature and pressure of the system. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant increases. This is because at lower temperatures and pressures, the refrigerant molecules are more closely packed together and require more energy to break the intermolecular forces and convert into a gas.
Explanation:
When the temperature of the refrigerant is lowered, the intermolecular forces between the molecules become stronger, and the molecules become more closely packed together. This results in an increase in the latent heat of vaporisation as more energy is required to break the intermolecular forces and convert the refrigerant into a gas.
Similarly, when the pressure of the refrigerant is lowered, the distance between the molecules increases, and the intermolecular forces become weaker. This results in an increase in the latent heat of vaporisation as more energy is required to overcome the weaker intermolecular forces and convert the refrigerant into a gas.
Conclusion:
In conclusion, the latent heat of vaporisation of a refrigerant increases at lower temperatures and pressures. This is an important consideration in the design and operation of refrigeration systems, as it determines the amount of heat that can be removed from the cooling space.
One ton refrigeration corresponds to- a)50 kcal/min
- b)50 kcal/kr
- c)80 kcal/day
- d)80 kcal/hr
- e)1000 kcal/day
Correct answer is option 'A'. Can you explain this answer?
One ton refrigeration corresponds to
a)
50 kcal/min
b)
50 kcal/kr
c)
80 kcal/day
d)
80 kcal/hr
e)
1000 kcal/day
|
|
Milan Ghosh answered |
One ton refrigeration corresponds to 50 kcal/min.
Explanation:
Refrigeration is the process of removing heat from a substance or space to lower its temperature. It is measured in units of refrigeration, commonly known as tons of refrigeration.
- One ton refrigeration is defined as the amount of heat required to melt one ton (2000 pounds) of ice at 32°F (0°C) in 24 hours. It is equivalent to 12,000 British thermal units (BTU) per hour or 211 kilocalories per minute.
- To convert it to kilocalories per minute, we divide 12,000 BTU/hr by 60 minutes per hour. This gives us 200 BTU/min.
- To convert BTU to kilocalories, we use the conversion factor 1 BTU = 0.252 kcal. Therefore, 200 BTU/min is equal to 200 * 0.252 = 50.4 kcal/min.
- However, since the options provided do not include decimal values, we round down to the nearest whole number. Hence, one ton refrigeration corresponds to 50 kcal/min.
- Option A, which states that one ton refrigeration corresponds to 50 kcal/min, is the correct answer.
In summary, one ton refrigeration is a measure of cooling capacity, and it corresponds to 50 kcal/min, which represents the amount of heat that can be removed per minute to achieve a cooling effect equivalent to melting one ton of ice in 24 hours.
Explanation:
Refrigeration is the process of removing heat from a substance or space to lower its temperature. It is measured in units of refrigeration, commonly known as tons of refrigeration.
- One ton refrigeration is defined as the amount of heat required to melt one ton (2000 pounds) of ice at 32°F (0°C) in 24 hours. It is equivalent to 12,000 British thermal units (BTU) per hour or 211 kilocalories per minute.
- To convert it to kilocalories per minute, we divide 12,000 BTU/hr by 60 minutes per hour. This gives us 200 BTU/min.
- To convert BTU to kilocalories, we use the conversion factor 1 BTU = 0.252 kcal. Therefore, 200 BTU/min is equal to 200 * 0.252 = 50.4 kcal/min.
- However, since the options provided do not include decimal values, we round down to the nearest whole number. Hence, one ton refrigeration corresponds to 50 kcal/min.
- Option A, which states that one ton refrigeration corresponds to 50 kcal/min, is the correct answer.
In summary, one ton refrigeration is a measure of cooling capacity, and it corresponds to 50 kcal/min, which represents the amount of heat that can be removed per minute to achieve a cooling effect equivalent to melting one ton of ice in 24 hours.
The thermodynamic cycle used in aircraft refrigeration is- a)reversed Carnot
- b)reversed Brayton
- c)vapour Compression cycle
- d)reversed Stirling
Correct answer is option 'B'. Can you explain this answer?
The thermodynamic cycle used in aircraft refrigeration is
a)
reversed Carnot
b)
reversed Brayton
c)
vapour Compression cycle
d)
reversed Stirling
|
Sagarika Patel answered |
The Brayton cycle is a thermodynamic cycle named after George Brayton who describes the workings of a constant-pressure heat engine. ... Reversed Joule cycle used as external heat and incorporates the use of a regenerator.
Chapter doubts & questions for Refrigeration & Air Conditioning - 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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