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All questions of Boiling & Condensation for Mechanical Engineering Exam
Which parameter is responsible for commencement of the turbulent flow?- a)Fourier number
- b)Reynolds number
- c)Stanton number
- d)Nusselt number
Correct answer is option 'B'. Can you explain this answer?
Which parameter is responsible for commencement of the turbulent flow?
a)
Fourier number
b)
Reynolds number
c)
Stanton number
d)
Nusselt number
|
Ishani Kaur answered |
The character of condensate film can range from laminar to highly turbulent.
An electric wire of 1.25 mm diameter and 250 mm long is laid horizontally and submerged in water at 7 bar. The wire has an applied voltage of 2.2 V and carries a current of 130 amperes. If the surface of the wire is maintained at 200 degree Celsius, make calculations for the heat flux- a)0.0915 * 10 6 W/m2
- b)0.1915 * 10 6 W/m2
- c)0.2915 * 10 6 W/m2
- d)0.3915 * 10 6 W/m2
Correct answer is option 'C'. Can you explain this answer?
An electric wire of 1.25 mm diameter and 250 mm long is laid horizontally and submerged in water at 7 bar. The wire has an applied voltage of 2.2 V and carries a current of 130 amperes. If the surface of the wire is maintained at 200 degree Celsius, make calculations for the heat flux
a)
0.0915 * 10 6 W/m2
b)
0.1915 * 10 6 W/m2
c)
0.2915 * 10 6 W/m2
d)
0.3915 * 10 6 W/m2
|
Shraddha Nair answered |
Q= V I = 286 W and A = 9.81 * 10 -4 m2. Therefore heat flux = Q/A.
The convective coefficients for condensation usually lie in the range- a)30-300 W/m2 K
- b)60-3000 W/m2 K
- c)300-10000 W/m2 K
- d)2500-10000 W/m2 K
Correct answer is option 'D'. Can you explain this answer?
The convective coefficients for condensation usually lie in the range
a)
30-300 W/m2 K
b)
60-3000 W/m2 K
c)
300-10000 W/m2 K
d)
2500-10000 W/m2 K
|
Nitya Banerjee answered |
The convective coefficient for condensation should be high because condensation refers to a change from the vapor to a liquid phase.
In condensation over a vertical surface, the value of convection coefficient varies as- a)k 0.25
- b)k 0.33
- c)k 0.75
- d)k -0.5
Correct answer is option 'A'. Can you explain this answer?
In condensation over a vertical surface, the value of convection coefficient varies as
a)
k 0.25
b)
k 0.33
c)
k 0.75
d)
k -0.5
|
Aashna Datta answered |
h = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25.
Which type of boiling occurs in steam boilers employing natural convection?- a)Forced convection
- b)Pool
- c)Local
- d)Saturated
Correct answer is option 'B'. Can you explain this answer?
Which type of boiling occurs in steam boilers employing natural convection?
a)
Forced convection
b)
Pool
c)
Local
d)
Saturated
|
|
Rajveer Rane answered |
The liquid above the hot surface is essentially stagnant and the only motion near the surface is because of free convection.
In which type of boiling the temperature of the liquid exceeds the saturation temperature?- a)Forced
- b)Natural
- c)Pool
- d)Saturated
Correct answer is option 'D'. Can you explain this answer?
In which type of boiling the temperature of the liquid exceeds the saturation temperature?
a)
Forced
b)
Natural
c)
Pool
d)
Saturated
|
Advait Chatterjee answered |
Explanation:
Boiling is a phase transition from the liquid phase to the vapor phase that occurs when the vapor pressure of the liquid equals or exceeds its atmospheric pressure. Boiling can occur in various types, including forced boiling, natural boiling, pool boiling, and saturated boiling.
Saturated boiling is a type of boiling where the temperature of the liquid exceeds its saturation temperature. The saturation temperature is the temperature at which a liquid boils at a given pressure. In saturated boiling, the liquid is already at its boiling point, but due to external heating or pressure conditions, the temperature of the liquid exceeds the saturation temperature. This can happen in certain conditions, such as:
- High pressure: When the pressure on the liquid is increased significantly, the saturation temperature also increases. If the liquid is heated beyond this increased saturation temperature, it will enter the saturated boiling region.
- Superheating: Superheating occurs when the liquid is heated above its boiling point without boiling. In this case, the liquid temperature exceeds the saturation temperature, and when a nucleation site or disturbance is introduced, rapid boiling can occur. This can happen, for example, when heating a liquid in a very clean container without any impurities or nucleation sites.
In both these cases, the temperature of the liquid exceeds the saturation temperature, thus leading to saturated boiling. Saturated boiling can have different effects and consequences depending on the system and conditions, such as heat transfer rates, pressure changes, and stability of the boiling process.
Conclusion:
In the given options, saturated boiling is the type of boiling where the temperature of the liquid exceeds the saturation temperature. Forced boiling, natural boiling, and pool boiling do not necessarily involve the liquid exceeding the saturation temperature.
Boiling is a phase transition from the liquid phase to the vapor phase that occurs when the vapor pressure of the liquid equals or exceeds its atmospheric pressure. Boiling can occur in various types, including forced boiling, natural boiling, pool boiling, and saturated boiling.
Saturated boiling is a type of boiling where the temperature of the liquid exceeds its saturation temperature. The saturation temperature is the temperature at which a liquid boils at a given pressure. In saturated boiling, the liquid is already at its boiling point, but due to external heating or pressure conditions, the temperature of the liquid exceeds the saturation temperature. This can happen in certain conditions, such as:
- High pressure: When the pressure on the liquid is increased significantly, the saturation temperature also increases. If the liquid is heated beyond this increased saturation temperature, it will enter the saturated boiling region.
- Superheating: Superheating occurs when the liquid is heated above its boiling point without boiling. In this case, the liquid temperature exceeds the saturation temperature, and when a nucleation site or disturbance is introduced, rapid boiling can occur. This can happen, for example, when heating a liquid in a very clean container without any impurities or nucleation sites.
In both these cases, the temperature of the liquid exceeds the saturation temperature, thus leading to saturated boiling. Saturated boiling can have different effects and consequences depending on the system and conditions, such as heat transfer rates, pressure changes, and stability of the boiling process.
Conclusion:
In the given options, saturated boiling is the type of boiling where the temperature of the liquid exceeds the saturation temperature. Forced boiling, natural boiling, and pool boiling do not necessarily involve the liquid exceeding the saturation temperature.
All the following statements are correct, except- a)Nucleate boiling gets promoted on a smooth surface
- b)In subcooled heating, the temperature of the heating surface is more than the boiling point of the liquid
- c)Film boiling region is usually avoided in commercial equipment
- d)There occurs transition from nucleate to film boiling burn-out point on the boiling curve
Correct answer is option 'A'. Can you explain this answer?
All the following statements are correct, except
a)
Nucleate boiling gets promoted on a smooth surface
b)
In subcooled heating, the temperature of the heating surface is more than the boiling point of the liquid
c)
Film boiling region is usually avoided in commercial equipment
d)
There occurs transition from nucleate to film boiling burn-out point on the boiling curve
|
Bhargavi Mukherjee answered |
A rough surface gives a better heat transmission than when the surface is either smooth or has been coated to weak its tendency to get wetted.
Condensation refers to a change from the- a)Solid to a liquid phase
- b)Vapor to a liquid phase
- c)Liquid to a solid phase
- d)Liquid to a vapor phase
Correct answer is option 'B'. Can you explain this answer?
Condensation refers to a change from the
a)
Solid to a liquid phase
b)
Vapor to a liquid phase
c)
Liquid to a solid phase
d)
Liquid to a vapor phase
|
Saanvi Chauhan answered |
Condensation is a convective heat transfer process that is associated with change in the phase of a fluid.
Condensation process is very common in
(i) Boilers
(ii) Condensers
(iii) Evaporators
Identify the correct statements- a)1 and 2
- b)2 and 3
- c)1, 2 and 3
- d)1 and 3
Correct answer is option 'C'. Can you explain this answer?
Condensation process is very common in
(i) Boilers
(ii) Condensers
(iii) Evaporators
Identify the correct statements
(i) Boilers
(ii) Condensers
(iii) Evaporators
Identify the correct statements
a)
1 and 2
b)
2 and 3
c)
1, 2 and 3
d)
1 and 3
|
Geetika Roy answered |
This process is very common in power plants and refrigeration systems.
When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection and the film coefficient follows the relation- a)Nu = f 1 (G r) f 2 (P r)
- b)Nu = 2 f 1 (G r) f 2 (P r)
- c)Nu = 3 f 1 (G r) f 2 (P r)
- d)Nu = 4 f 1 (G r) f 2 (P r)
Correct answer is option 'A'. Can you explain this answer?
When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection and the film coefficient follows the relation
a)
Nu = f 1 (G r) f 2 (P r)
b)
Nu = 2 f 1 (G r) f 2 (P r)
c)
Nu = 3 f 1 (G r) f 2 (P r)
d)
Nu = 4 f 1 (G r) f 2 (P r)
|
|
Rajat Saini answered |
Explanation:
Evaporation at the liquid-vapor interface:
- When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection.
- This means that heat is transferred through the movement of the fluid itself.
Film coefficient relation:
- The film coefficient in this case can be related using the Nusselt number (Nu) which follows the relation: Nu = f1(G r) f2(P r).
- Here, Nu is the Nusselt number, G r is the Grashof number, and P r is the Prandtl number.
- The function f1 and f2 are dimensionless functions that depend on the flow regime and fluid properties.
Answer:
- The correct relation for the film coefficient in this scenario is given by: Nu = f1(G r) f2(P r).
- This relation takes into account the Grashof and Prandtl numbers which are important parameters in free convection heat transfer.
- Therefore, option 'A' is the correct answer for this question.
Evaporation at the liquid-vapor interface:
- When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection.
- This means that heat is transferred through the movement of the fluid itself.
Film coefficient relation:
- The film coefficient in this case can be related using the Nusselt number (Nu) which follows the relation: Nu = f1(G r) f2(P r).
- Here, Nu is the Nusselt number, G r is the Grashof number, and P r is the Prandtl number.
- The function f1 and f2 are dimensionless functions that depend on the flow regime and fluid properties.
Answer:
- The correct relation for the film coefficient in this scenario is given by: Nu = f1(G r) f2(P r).
- This relation takes into account the Grashof and Prandtl numbers which are important parameters in free convection heat transfer.
- Therefore, option 'A' is the correct answer for this question.
A 0.10 cm diameter and 15 cm long wire has been laid horizontally and submerged in water at atmospheric pressure. The wire has a steady state voltage drop of 14.5 V and a current of 42.5 A. Determine the heat flux of the wire.
The following equation applies for water boiling on a horizontal submerged surface
H = 1.54 (Q/A) 0.75 = 5.58 (d t) 3 W/m2 K where Q/A is the heat flux rate in W/m2 and d t is the temperature difference between surface and saturation- a)1.308 * 10 8 W/m2
- b)1.308 * 10 7 W/m2
- c)1.308 * 10 6 W/m2
- d)1.308 * 10 5 W/m2
Correct answer is option 'C'. Can you explain this answer?
A 0.10 cm diameter and 15 cm long wire has been laid horizontally and submerged in water at atmospheric pressure. The wire has a steady state voltage drop of 14.5 V and a current of 42.5 A. Determine the heat flux of the wire.
The following equation applies for water boiling on a horizontal submerged surface
H = 1.54 (Q/A) 0.75 = 5.58 (d t) 3 W/m2 K where Q/A is the heat flux rate in W/m2 and d t is the temperature difference between surface and saturation
The following equation applies for water boiling on a horizontal submerged surface
H = 1.54 (Q/A) 0.75 = 5.58 (d t) 3 W/m2 K where Q/A is the heat flux rate in W/m2 and d t is the temperature difference between surface and saturation
a)
1.308 * 10 8 W/m2
b)
1.308 * 10 7 W/m2
c)
1.308 * 10 6 W/m2
d)
1.308 * 10 5 W/m2
|
|
Prasad Menon answered |
Q = E I = 616.25 W and A = 4.71 * 10 -4 m2.
The excess temperature range 50 degree Celsius < d t < 200 degree Celsius is indicative of the region of- a)Interface evaporation
- b)Nuclear boiling
- c)Partial film boiling
- d)Stable film boiling
Correct answer is option 'C'. Can you explain this answer?
The excess temperature range 50 degree Celsius < d t < 200 degree Celsius is indicative of the region of
a)
Interface evaporation
b)
Nuclear boiling
c)
Partial film boiling
d)
Stable film boiling
|
|
Nikhil Choudhury answered |
The physical phenomenon of pool boiling is generally divided into four different regions based on the excess temperature.
Mark the wrong statement with respect to laminar flow condensation on a vertical plate- a)The rate of condensation heat transfer is maximum at the upper edge of the plate and progressively decreases as the lower edge is approached
- b)The average heat transfer coefficient is two third of the local heat transfer coefficient at the lower edge of the plate
- c)At a definite point on the heat transfer, the film coefficient is directly proportional to thermal conductivity and inversely proportional to thickness of film at the point
- d)The film thickness increases as the fourth root of the distance down the upper edge
Correct answer is option 'B'. Can you explain this answer?
Mark the wrong statement with respect to laminar flow condensation on a vertical plate
a)
The rate of condensation heat transfer is maximum at the upper edge of the plate and progressively decreases as the lower edge is approached
b)
The average heat transfer coefficient is two third of the local heat transfer coefficient at the lower edge of the plate
c)
At a definite point on the heat transfer, the film coefficient is directly proportional to thermal conductivity and inversely proportional to thickness of film at the point
d)
The film thickness increases as the fourth root of the distance down the upper edge
|
|
Nitin Malik answered |
The average heat transfer coefficient is 4/3 of the local heat transfer coefficient at the lower edge of the plate.
Maximum heat transfer rate in a modern boiler is about- a)2 * 10 5 W/m2
- b)3 * 10 5 W/m2
- c)4 * 10 5 W/m2
- d)5 * 10 5 W/m2
Correct answer is option 'A'. Can you explain this answer?
Maximum heat transfer rate in a modern boiler is about
a)
2 * 10 5 W/m2
b)
3 * 10 5 W/m2
c)
4 * 10 5 W/m2
d)
5 * 10 5 W/m2
|
|
Pranab Joshi answered |
Greater importance has recently been given to the boiling heat transfer.
For laminar film condensation on a vertical plate, the film thickness is given by- a)[4 k δ (t sat – t s) x/p 2 g h f g] 0.25
- b)[4 k δ (t sat – t s) x/p 2 g h f g] 0.5
- c)[4 k δ (t sat – t s) x/p 2 g h f g]
- d)[4 k δ (t sat – t s) x/p 2 g h f g] 1.5
Correct answer is option 'A'. Can you explain this answer?
For laminar film condensation on a vertical plate, the film thickness is given by
a)
[4 k δ (t sat – t s) x/p 2 g h f g] 0.25
b)
[4 k δ (t sat – t s) x/p 2 g h f g] 0.5
c)
[4 k δ (t sat – t s) x/p 2 g h f g]
d)
[4 k δ (t sat – t s) x/p 2 g h f g] 1.5
|
|
Shruti Sen answered |
The film thickness increases as the fourth root of the distance down the surface.
What is the value of surface fluid constant for water-copper combination?- a)0.010
- b)0.011
- c)0.012
- d)0.013
Correct answer is option 'D'. Can you explain this answer?
What is the value of surface fluid constant for water-copper combination?
a)
0.010
b)
0.011
c)
0.012
d)
0.013
|
Shivani Patel answered |
The value of the surface fluid constant for a water-copper combination is 0.013.
Explanation:
The surface fluid constant, also known as the interfacial tension, is a property that represents the force per unit length acting at the interface between two immiscible fluids. It quantifies the degree of attraction or repulsion between the two fluids.
In the case of a water-copper combination, the interfacial tension determines the wetting behavior of water on the copper surface. Wetting refers to the ability of a liquid to spread across a solid surface. If the interfacial tension is low, water will spread easily on the copper surface, indicating good wetting. On the other hand, if the interfacial tension is high, water will tend to bead up on the surface, indicating poor wetting.
The value of the surface fluid constant for a specific fluid combination depends on the nature of the fluids and the characteristics of the interface. It can be determined experimentally by measuring the contact angle between the fluid and the solid surface.
In the case of a water-copper combination, the value of the surface fluid constant has been determined to be 0.013. This value indicates that water wets the copper surface well, as the interfacial tension between water and copper is relatively low.
Wetting is an important property in various industrial applications, such as coating processes, heat exchangers, and microfluidic devices. Understanding the wetting behavior of different fluid-solid combinations helps in optimizing these processes and improving their efficiency.
In summary, the value of the surface fluid constant for a water-copper combination is 0.013, indicating good wetting behavior of water on the copper surface.
Explanation:
The surface fluid constant, also known as the interfacial tension, is a property that represents the force per unit length acting at the interface between two immiscible fluids. It quantifies the degree of attraction or repulsion between the two fluids.
In the case of a water-copper combination, the interfacial tension determines the wetting behavior of water on the copper surface. Wetting refers to the ability of a liquid to spread across a solid surface. If the interfacial tension is low, water will spread easily on the copper surface, indicating good wetting. On the other hand, if the interfacial tension is high, water will tend to bead up on the surface, indicating poor wetting.
The value of the surface fluid constant for a specific fluid combination depends on the nature of the fluids and the characteristics of the interface. It can be determined experimentally by measuring the contact angle between the fluid and the solid surface.
In the case of a water-copper combination, the value of the surface fluid constant has been determined to be 0.013. This value indicates that water wets the copper surface well, as the interfacial tension between water and copper is relatively low.
Wetting is an important property in various industrial applications, such as coating processes, heat exchangers, and microfluidic devices. Understanding the wetting behavior of different fluid-solid combinations helps in optimizing these processes and improving their efficiency.
In summary, the value of the surface fluid constant for a water-copper combination is 0.013, indicating good wetting behavior of water on the copper surface.
The boiling phenomenon is known to occur in how many forms?- a)1
- b)2
- c)3
- d)4
Correct answer is option 'D'. Can you explain this answer?
The boiling phenomenon is known to occur in how many forms?
a)
1
b)
2
c)
3
d)
4
|
|
Pranab Joshi answered |
Pool, forced convection, subcooled and saturated boiling.
The transition from laminar to turbulent flow occurs at a critical Reynolds number of- a)1800
- b)2200
- c)2600
- d)3000
Correct answer is option 'A'. Can you explain this answer?
The transition from laminar to turbulent flow occurs at a critical Reynolds number of
a)
1800
b)
2200
c)
2600
d)
3000
|
|
Uday Mukherjee answered |
For turbulent film condensation on vertical surfaces, Kirk bride has suggested the correlation for the average heat transfer coefficient which is valid for Reynolds number greater than 1800.
In nucleate pool boiling, the heat flux depends on- a)Liquid properties, material and condition of the surface
- b)Material of the surface only
- c)Material and roughness of the surface
- d)Liquid properties and material of the surface
Correct answer is option 'A'. Can you explain this answer?
In nucleate pool boiling, the heat flux depends on
a)
Liquid properties, material and condition of the surface
b)
Material of the surface only
c)
Material and roughness of the surface
d)
Liquid properties and material of the surface
|
Milan Sen answered |
The heat flux must depends on liquid properties material and condition of the surface.
A condenser is to be designed to condense 225.0 kg of steam per hour at a pressure of 0.15 bar. A square array of 400 tubes, each of 6 mm in diameter, is available for the task. If the tube surface temperature is to be maintained at 26 degree Celsius, make calculations for the length of the tube- a)4.353 m
- b)3.353 m
- c)2.353 m
- d)1.353 m
Correct answer is option 'D'. Can you explain this answer?
A condenser is to be designed to condense 225.0 kg of steam per hour at a pressure of 0.15 bar. A square array of 400 tubes, each of 6 mm in diameter, is available for the task. If the tube surface temperature is to be maintained at 26 degree Celsius, make calculations for the length of the tube
a)
4.353 m
b)
3.353 m
c)
2.353 m
d)
1.353 m
|
|
Shivani Patel answered |
t sat = 54 degree Celsius and h f g = 2373000 J/kg, t f = 40 degree Celsius and h v = 0.725 [k 3 g p 2 h f g/l δ (t sat – t s)] 0.25 = 5202.34 W/m2 K. Total S.A of 400 tubes = 7.536l and heat flow rate = m h f g.
A 1.0 mm diameter and 300 mm long nickel wire is submerged horizontal in water at atmospheric pressure. At burnout, the wire has a current of 195 A. Calculate the voltage at burnout. The relevant thermos-physical properties are
p f (fluid) = 959.52 kg/m3
p g (vapor) = 0.597 kg/m3
h f g = 2257000 J/kg
σ = 0.0533 N/m- a)6.15 V
- b)7.15 V
- c)8.15 V
- d)9.15 V
Correct answer is option 'B'. Can you explain this answer?
A 1.0 mm diameter and 300 mm long nickel wire is submerged horizontal in water at atmospheric pressure. At burnout, the wire has a current of 195 A. Calculate the voltage at burnout. The relevant thermos-physical properties are
p f (fluid) = 959.52 kg/m3
p g (vapor) = 0.597 kg/m3
h f g = 2257000 J/kg
σ = 0.0533 N/m
p f (fluid) = 959.52 kg/m3
p g (vapor) = 0.597 kg/m3
h f g = 2257000 J/kg
σ = 0.0533 N/m
a)
6.15 V
b)
7.15 V
c)
8.15 V
d)
9.15 V
|
|
Milan Sen answered |
(Q/A) MAX = 1480000 W/m2. Let E b be the voltage at burnout. Then electric energy input to wire is E b I = 195 E b W.
Leiden-frost expansion is related to- a)Condensation of vapor on a cold surface
- b)Exchange of heat between two solids
- c)Evaporation of a solution
- d)Boiling of liquid on a hot surface
Correct answer is option 'D'. Can you explain this answer?
Leiden-frost expansion is related to
a)
Condensation of vapor on a cold surface
b)
Exchange of heat between two solids
c)
Evaporation of a solution
d)
Boiling of liquid on a hot surface
|
|
Nikhil Kumar answered |
It is related to boiling of liquid on a hot surface.
For laminar film condensation on a vertical plate, the velocity distribution at a distance δ from the top edge is given by- a)p g (δ y – y/2)/σ
- b)p g (δ y – y 2)/σ
- c)p g (δ y – y 2/2)/σ
- d)p g (δ – y 2/2)/σ
Correct answer is option 'C'. Can you explain this answer?
For laminar film condensation on a vertical plate, the velocity distribution at a distance δ from the top edge is given by
a)
p g (δ y – y/2)/σ
b)
p g (δ y – y 2)/σ
c)
p g (δ y – y 2/2)/σ
d)
p g (δ – y 2/2)/σ
|
|
Dipika Banerjee answered |
An equation for the velocity distribution as a function of some distance from the wall surface can be set up by considering the equilibrium between the gravity and viscous forces on an elementary volume of the liquid film.
In which type of boiling the fluid motion is induced by external means?- a)Pool
- b)Local
- c)Forced convection
- d)Subcooled
Correct answer is option 'C'. Can you explain this answer?
In which type of boiling the fluid motion is induced by external means?
a)
Pool
b)
Local
c)
Forced convection
d)
Subcooled
|
|
Deepak Mehta answered |
The liquid is pumped and forced across the surface in a controlled manner.
For laminar film condensation on a vertical plate, the gravitational acceleration g is replaced byWhere, α is the inclination angle with the horizontal- a)4 g sin α
- b)3 g sin α
- c)2 g sin α
- d)g sin α
Correct answer is option 'D'. Can you explain this answer?
For laminar film condensation on a vertical plate, the gravitational acceleration g is replaced by
Where, α is the inclination angle with the horizontal
a)
4 g sin α
b)
3 g sin α
c)
2 g sin α
d)
g sin α
|
|
Rohit Banerjee answered |
It is replaced by sin α.
Spherical bubbles of 3 mm diameter are observed in the bulk fluid boiling of water at standard atmospheric pressure. Assuming pure water vapor in the bubble and vapor pressure equal to 101.325 k N/m2, calculate the temperature of the vapor- a)100.217 degree Celsius
- b)200.217 degree Celsius
- c)300.217 degree Celsius
- d)400.217 degree Celsius
Correct answer is option 'A'. Can you explain this answer?
Spherical bubbles of 3 mm diameter are observed in the bulk fluid boiling of water at standard atmospheric pressure. Assuming pure water vapor in the bubble and vapor pressure equal to 101.325 k N/m2, calculate the temperature of the vapor
a)
100.217 degree Celsius
b)
200.217 degree Celsius
c)
300.217 degree Celsius
d)
400.217 degree Celsius
|
|
Shanaya Bose answered |
Calculation of Vaporization Temperature of Water
Given:
Diameter of bubble (d) = 3 mm = 0.003 m
Vapor Pressure of water (Pv) = 101.325 kN/m2
Formula used:
We will use the Laplace's equation to calculate the vaporization temperature of water.
Laplace's equation:
Pv = 2σ/r
Where,
Pv = Vapor Pressure
σ = Surface Tension
r = radius of the bubble
Surface Tension of water (σ) at room temperature is 71.97 mN/m.
Calculation:
We can calculate the radius of bubble (r) from its diameter (d) as follows:
r = d/2 = 0.003/2 = 0.0015 m
Substituting the given values in Laplace's equation:
101.325 × 10^3 = 2 × 71.97 × 10^-3 / 0.0015
101.325 × 10^3 = 95.96 × 10^3 / r
r = 95.96 × 10^3 / 101.325 × 10^3
r = 0.946 m
We can now use the Clausius-Clapeyron equation to calculate the vaporization temperature of water:
ln(Pv/P) = ΔHvap/R(1/Tvap-1/T)
Where,
Pv = Vapor Pressure
P = Atmospheric Pressure
ΔHvap = Enthalpy of vaporization
R = Gas Constant
Tvap = Vaporization Temperature
T = Temperature of water
Assuming the enthalpy of vaporization of water (ΔHvap) at 100 °C to be 40.67 kJ/mol and the gas constant (R) to be 8.314 J/mol-K, we can rewrite the equation as:
ln(101.325 × 10^3/101.325 × 10^3) = 40.67 × 10^3 / 8.314 (1/Tvap - 1/373.15)
Simplifying the equation, we get:
1/Tvap = 1/373.15 + ln(101.325 × 10^3/101.325 × 10^3) × 8.314 / 40.67 × 10^3
1/Tvap = 1/373.15
Tvap = 373.15 K - 273.15
Tvap = 100.217 °C
Therefore, the temperature of the vapor in the bubble is 100.217 °C.
Given:
Diameter of bubble (d) = 3 mm = 0.003 m
Vapor Pressure of water (Pv) = 101.325 kN/m2
Formula used:
We will use the Laplace's equation to calculate the vaporization temperature of water.
Laplace's equation:
Pv = 2σ/r
Where,
Pv = Vapor Pressure
σ = Surface Tension
r = radius of the bubble
Surface Tension of water (σ) at room temperature is 71.97 mN/m.
Calculation:
We can calculate the radius of bubble (r) from its diameter (d) as follows:
r = d/2 = 0.003/2 = 0.0015 m
Substituting the given values in Laplace's equation:
101.325 × 10^3 = 2 × 71.97 × 10^-3 / 0.0015
101.325 × 10^3 = 95.96 × 10^3 / r
r = 95.96 × 10^3 / 101.325 × 10^3
r = 0.946 m
We can now use the Clausius-Clapeyron equation to calculate the vaporization temperature of water:
ln(Pv/P) = ΔHvap/R(1/Tvap-1/T)
Where,
Pv = Vapor Pressure
P = Atmospheric Pressure
ΔHvap = Enthalpy of vaporization
R = Gas Constant
Tvap = Vaporization Temperature
T = Temperature of water
Assuming the enthalpy of vaporization of water (ΔHvap) at 100 °C to be 40.67 kJ/mol and the gas constant (R) to be 8.314 J/mol-K, we can rewrite the equation as:
ln(101.325 × 10^3/101.325 × 10^3) = 40.67 × 10^3 / 8.314 (1/Tvap - 1/373.15)
Simplifying the equation, we get:
1/Tvap = 1/373.15 + ln(101.325 × 10^3/101.325 × 10^3) × 8.314 / 40.67 × 10^3
1/Tvap = 1/373.15
Tvap = 373.15 K - 273.15
Tvap = 100.217 °C
Therefore, the temperature of the vapor in the bubble is 100.217 °C.
The outer surface of a vertical tube is 1.25 m long and outer diameter is 50 mm is exposed to saturated steam at atmospheric pressure. If the tube surface is maintained at 80 degree Celsius by the flow of cooling water through it, determine the rate of heat transfer to the coolant- a)47648 W
- b)12345 W
- c)19879 W
- d)97123 W
Correct answer is option 'C'. Can you explain this answer?
The outer surface of a vertical tube is 1.25 m long and outer diameter is 50 mm is exposed to saturated steam at atmospheric pressure. If the tube surface is maintained at 80 degree Celsius by the flow of cooling water through it, determine the rate of heat transfer to the coolant
a)
47648 W
b)
12345 W
c)
19879 W
d)
97123 W
|
|
Preethi Das answered |
h v = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25 = 5046.8 W/m 2 k and heat flow rate = 19879 W.
Identify the wrong statement with respect to boiling heat transfer?- a)The steam boilers employing natural convection have steam raised through pool boiling
- b)Boiling occurs when a heated surface is exposed to a liquid and maintained at a temperature lower than the saturation temperature of the liquid
- c)Leiden-frost effect refers to the phenomenon of stable film boiling
- d)The nucleation boiling is characterized by the formation of bubbles at the nucleation sites and the resulting liquid agitation
Correct answer is option 'B'. Can you explain this answer?
Identify the wrong statement with respect to boiling heat transfer?
a)
The steam boilers employing natural convection have steam raised through pool boiling
b)
Boiling occurs when a heated surface is exposed to a liquid and maintained at a temperature lower than the saturation temperature of the liquid
c)
Leiden-frost effect refers to the phenomenon of stable film boiling
d)
The nucleation boiling is characterized by the formation of bubbles at the nucleation sites and the resulting liquid agitation
|
|
Sagarika Chopra answered |
For boiling to occur, the heated surface must be exposed to a liquid and maintained at a temperature higher than the saturation temperature of the liquid.
For film wise condensation on a vertical plane, the film thickness δ and heat transfer coefficient h vary with distance x from the leading edge as- a)δ decreases, h increases
- b)Both δ and h increases
- c)δ increases, h decreases
- d)Both δ and h decreases
Correct answer is option 'C'. Can you explain this answer?
For film wise condensation on a vertical plane, the film thickness δ and heat transfer coefficient h vary with distance x from the leading edge as
a)
δ decreases, h increases
b)
Both δ and h increases
c)
δ increases, h decreases
d)
Both δ and h decreases
|
|
Akshat Chawla answered |
Thickness increases and heat transfer coefficient decreases.
For laminar film condensation on a vertical plate, the local heat transfer coefficient at the lower edge of the plate is given by- a)[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.25
- b)[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.5
- c)[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.1
- d)[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.125
Correct answer is option 'A'. Can you explain this answer?
For laminar film condensation on a vertical plate, the local heat transfer coefficient at the lower edge of the plate is given by
a)
[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.25
b)
[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.5
c)
[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.1
d)
[k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.125
|
|
Saanvi Chauhan answered |
The rate of condensation heat transfer is higher at the upper end of the plate than at the lower end.
A plate condenser was designed to be kept vertical. How would the condensation coefficient be effected if due to site constraints, it has to be kept at 60 degree to the horizontal?- a)1.53% reduction in condensation coefficient
- b)2.53% reduction in condensation coefficient
- c)3.53% reduction in condensation coefficient
- d)4.53% reduction in condensation coefficient
Correct answer is option 'C'. Can you explain this answer?
A plate condenser was designed to be kept vertical. How would the condensation coefficient be effected if due to site constraints, it has to be kept at 60 degree to the horizontal?
a)
1.53% reduction in condensation coefficient
b)
2.53% reduction in condensation coefficient
c)
3.53% reduction in condensation coefficient
d)
4.53% reduction in condensation coefficient
|
|
Nitya Banerjee answered |
h VER = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25, h INC = 0.943 [k 3 p 2 g sin α h f g/δ l (t sat – t s)] 0.
Natural convection heat transfer coefficients over surface of a vertical pipe and a vertical flat plate for same height. What is/are the possible reasons for this?
(i) Same height
(ii) Both vertical
(iii) Same fluid
(iv) Same fluid flow pattern
Select the correct answer- a)4
- b)1 and 2
- c)1
- d)3 and 4
Correct answer is option 'D'. Can you explain this answer?
Natural convection heat transfer coefficients over surface of a vertical pipe and a vertical flat plate for same height. What is/are the possible reasons for this?
(i) Same height
(ii) Both vertical
(iii) Same fluid
(iv) Same fluid flow pattern
Select the correct answer
(i) Same height
(ii) Both vertical
(iii) Same fluid
(iv) Same fluid flow pattern
Select the correct answer
a)
4
b)
1 and 2
c)
1
d)
3 and 4
|
|
Dhruba Kapoor answered |
The fluids must be same so their flow pattern.
Milk spills over when it is boiled in an open vessel. The boiling of milk at this instant is referred to as- a)Interface evaporation
- b)Sub-cooled boiling
- c)Film boiling
- d)Saturated nucleate boiling
Correct answer is option 'B'. Can you explain this answer?
Milk spills over when it is boiled in an open vessel. The boiling of milk at this instant is referred to as
a)
Interface evaporation
b)
Sub-cooled boiling
c)
Film boiling
d)
Saturated nucleate boiling
|
|
Athira Bajaj answered |
This is an application of sub-cooled boiling.
Kirk bride criterion is given by- a)h = 0.0057 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
- b)h = 0.0067 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
- c)h = 0.0077 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
- d)h = 0.0087 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
Correct answer is option 'C'. Can you explain this answer?
Kirk bride criterion is given by
a)
h = 0.0057 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
b)
h = 0.0067 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
c)
h = 0.0077 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
d)
h = 0.0087 (Re) 0.4 [k 3 p 2 g/δ 2] 1/3
|
|
Gargi Desai answered |
This is valid for Re greater than 1800.
The phenomenon of stable film boiling is referred to as- a)Nucleate effect
- b)Boiling regimes
- c)Leiden frost effect
- d)Von karma effect
Correct answer is option 'C'. Can you explain this answer?
The phenomenon of stable film boiling is referred to as
a)
Nucleate effect
b)
Boiling regimes
c)
Leiden frost effect
d)
Von karma effect
|
|
Niharika Kaur answered |
This is the region of stable film boiling.
A plate condenser of dimensions l * b has been designed to be kept with side l in the vertical position. However due to oversight during erection and installation, it was fixed with side b vertical. How would this affect the heat transfer? Assume laminar conditions and same thermos-physical properties and take b = l/2- a)The condenser should be installed with shorter side horizontal
- b)The condenser should be installed with longer side horizontal
- c)The condenser should be installed with longer side vertical
- d)The condenser should be installed with shorter side vertical
Correct answer is option 'D'. Can you explain this answer?
A plate condenser of dimensions l * b has been designed to be kept with side l in the vertical position. However due to oversight during erection and installation, it was fixed with side b vertical. How would this affect the heat transfer? Assume laminar conditions and same thermos-physical properties and take b = l/2
a)
The condenser should be installed with shorter side horizontal
b)
The condenser should be installed with longer side horizontal
c)
The condenser should be installed with longer side vertical
d)
The condenser should be installed with shorter side vertical
|
|
Akshay Mehta answered |
h 1 = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25, h2 = 0.943 [k 3 p 2 g h f g/δ b (t sat – t s)] 0.25. So, h 1/h 2 = 0.8409.
Drop wise condensation usually occurs on- a)Oily surface
- b)Glazed surface
- c)Smooth surface
- d)Coated surface
Correct answer is option 'A'. Can you explain this answer?
Drop wise condensation usually occurs on
a)
Oily surface
b)
Glazed surface
c)
Smooth surface
d)
Coated surface
|
|
Baishali Roy answered |
Drop wise Condensation on Oily Surface
Definition of Drop wise Condensation:
Drop wise condensation is a process in which the vapor condenses into droplets on a surface. This process is different from film condensation, where the vapor condenses as a continuous film on the surface.
Explanation:
Drop wise condensation usually occurs on an oily surface. The reason for this is that the surface tension of the oil droplets is much higher than that of water droplets. When vapor condenses on an oily surface, it forms droplets that are relatively stable due to the high surface tension of the oil.
Characteristics of Oily Surface:
The characteristics of an oily surface, such as its surface tension, viscosity, and wettability, influence the drop wise condensation process. A surface with high surface tension and low wettability will promote drop wise condensation, while a surface with low surface tension and high wettability will promote film condensation.
Advantages of Drop wise Condensation on Oily Surface:
Drop wise condensation on an oily surface has several advantages over film condensation. The droplets formed during drop wise condensation have a larger surface area than the film formed during film condensation. This larger surface area leads to a higher heat transfer coefficient, which means that more heat can be transferred in a shorter amount of time.
Applications of Drop wise Condensation on Oily Surface:
Drop wise condensation on an oily surface is used in various industrial applications, such as in heat exchangers, distillation columns, and condensers. The use of drop wise condensation can improve the efficiency of these processes by increasing the heat transfer rate.
Conclusion:
In conclusion, drop wise condensation usually occurs on an oily surface due to the high surface tension of the oil droplets. This process has several advantages over film condensation and is used in various industrial applications to improve the efficiency of heat transfer processes.
Definition of Drop wise Condensation:
Drop wise condensation is a process in which the vapor condenses into droplets on a surface. This process is different from film condensation, where the vapor condenses as a continuous film on the surface.
Explanation:
Drop wise condensation usually occurs on an oily surface. The reason for this is that the surface tension of the oil droplets is much higher than that of water droplets. When vapor condenses on an oily surface, it forms droplets that are relatively stable due to the high surface tension of the oil.
Characteristics of Oily Surface:
The characteristics of an oily surface, such as its surface tension, viscosity, and wettability, influence the drop wise condensation process. A surface with high surface tension and low wettability will promote drop wise condensation, while a surface with low surface tension and high wettability will promote film condensation.
Advantages of Drop wise Condensation on Oily Surface:
Drop wise condensation on an oily surface has several advantages over film condensation. The droplets formed during drop wise condensation have a larger surface area than the film formed during film condensation. This larger surface area leads to a higher heat transfer coefficient, which means that more heat can be transferred in a shorter amount of time.
Applications of Drop wise Condensation on Oily Surface:
Drop wise condensation on an oily surface is used in various industrial applications, such as in heat exchangers, distillation columns, and condensers. The use of drop wise condensation can improve the efficiency of these processes by increasing the heat transfer rate.
Conclusion:
In conclusion, drop wise condensation usually occurs on an oily surface due to the high surface tension of the oil droplets. This process has several advantages over film condensation and is used in various industrial applications to improve the efficiency of heat transfer processes.
The boiling process has wide-spread applications in
(i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating
(ii) Absorption of heat in refrigeration and air-conditioning systems
(iii) Concentration, dehydration and drying of foods and materials
Identify the correct statements- a)1 and 2
- b)2 and 3
- c)1, 2 and 3
- d)1 and 3
Correct answer is option 'C'. Can you explain this answer?
The boiling process has wide-spread applications in
(i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating
(ii) Absorption of heat in refrigeration and air-conditioning systems
(iii) Concentration, dehydration and drying of foods and materials
Identify the correct statements
(i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating
(ii) Absorption of heat in refrigeration and air-conditioning systems
(iii) Concentration, dehydration and drying of foods and materials
Identify the correct statements
a)
1 and 2
b)
2 and 3
c)
1, 2 and 3
d)
1 and 3
|
|
Mira Pillai answered |
Boiling constitutes the convective heat transfer process that involves a phase change from liquid to vapor state.
In spite of large heat transfer coefficient in boiling liquids, fins are used advantageously when the entire surface is exposed to- a)Film boiling
- b)Transition boiling
- c)Nucleate boiling
- d)All modes of boiling
Correct answer is option 'D'. Can you explain this answer?
In spite of large heat transfer coefficient in boiling liquids, fins are used advantageously when the entire surface is exposed to
a)
Film boiling
b)
Transition boiling
c)
Nucleate boiling
d)
All modes of boiling
|
Sagarika Patel answered |
OPTION (D) IS CORRECT.
Here all modes of boiling i.e. film, transition and nucleate are of great importance.
Here all modes of boiling i.e. film, transition and nucleate are of great importance.
Consider the following statements
(i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it
(ii) Drop wise condensation gives a higher transfer rate than film wise condensation
(iii) Reynolds number of condensing liquid is based on its mass flow rate
(iv) Suitable coating or vapor additive is used to promote film wise condensation
Identify the correct statement- a)1 and 2
- b)2, 3 and 4
- c)4 only
- d)1, 2 and 3
Correct answer is option 'D'. Can you explain this answer?
Consider the following statements
(i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it
(ii) Drop wise condensation gives a higher transfer rate than film wise condensation
(iii) Reynolds number of condensing liquid is based on its mass flow rate
(iv) Suitable coating or vapor additive is used to promote film wise condensation
Identify the correct statement
(i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it
(ii) Drop wise condensation gives a higher transfer rate than film wise condensation
(iii) Reynolds number of condensing liquid is based on its mass flow rate
(iv) Suitable coating or vapor additive is used to promote film wise condensation
Identify the correct statement
a)
1 and 2
b)
2, 3 and 4
c)
4 only
d)
1, 2 and 3
|
Mrinalini Sen answered |
All are correct except the last one because suitable coating or vapor additive is not used to promote film wise condensation.
Determine the length of a 25 cm outer diameter tube if the condensate formed on the surface of the tube is to be same whether it is kept vertical or horizontal- a)61.5 cm
- b)71.5 cm
- c)81.5 cm
- d)91.5 cm
Correct answer is option 'B'. Can you explain this answer?
Determine the length of a 25 cm outer diameter tube if the condensate formed on the surface of the tube is to be same whether it is kept vertical or horizontal
a)
61.5 cm
b)
71.5 cm
c)
81.5 cm
d)
91.5 cm
|
|
Shounak Basu answered |
h v = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25, h H = 0.943 [k 3 p 2 g h f g/δ d (t sat– t s)] 0.25, l/d = 2.86.
Depending upon the behavior of condensate up on the cooled surface, the condensation process are classified into how many distinct modes?- a)1
- b)2
- c)3
- d)4
Correct answer is option 'B'. Can you explain this answer?
Depending upon the behavior of condensate up on the cooled surface, the condensation process are classified into how many distinct modes?
a)
1
b)
2
c)
3
d)
4
|
|
Shounak Basu answered |
Film condensation and drop wise condensation.
Saturated steam is allowed to condense over a vertical flat surface and the condensate film flows down the surface. The local coefficient of heat transfer for condensation- a)Remains constant at all heights of the surface
- b)Decreases with increasing distance from the top of the surface
- c)Increases with increasing thickness of film
- d)Increases with increasing temperature differential between the surface and vapour
Correct answer is option 'B'. Can you explain this answer?
Saturated steam is allowed to condense over a vertical flat surface and the condensate film flows down the surface. The local coefficient of heat transfer for condensation
a)
Remains constant at all heights of the surface
b)
Decreases with increasing distance from the top of the surface
c)
Increases with increasing thickness of film
d)
Increases with increasing temperature differential between the surface and vapour
|
|
Akshay Mehta answered |
It decreases with increasing thickness of condensate film.
Consider the following phenomena
(i) Boiling
(ii) Free convection in air
(iii) Forced convection in air
(iv) Conduction in air
Identify the correct sequence (heat transfer coefficient)- a)3 – 4 – 1 – 2
- b)4 – 1 – 3 – 2
- c)4 – 3 – 2 – 1
- d)4 – 2 – 3 – 1
Correct answer is option 'D'. Can you explain this answer?
Consider the following phenomena
(i) Boiling
(ii) Free convection in air
(iii) Forced convection in air
(iv) Conduction in air
Identify the correct sequence (heat transfer coefficient)
(i) Boiling
(ii) Free convection in air
(iii) Forced convection in air
(iv) Conduction in air
Identify the correct sequence (heat transfer coefficient)
a)
3 – 4 – 1 – 2
b)
4 – 1 – 3 – 2
c)
4 – 3 – 2 – 1
d)
4 – 2 – 3 – 1
|
|
Nikhil Kumar answered |
Heat transfer coefficient is maximum for conduction in air and is least for boiling.
Which of the following parameters affect burnout heat flux in the nucleate boiling region
(i) Heat of evaporation
(ii) Temperature difference
(iii) Density of vapor
(iv) Density of liquid
(v) Surface tension at the vapor-liquid interface
Mark the correct answer from the codes indicated below- a)1, 2, 3 and 5
- b)1, 3, 4 and 5
- c)1, 2, 3 and 4
- d)1, 3 and 5
Correct answer is option 'B'. Can you explain this answer?
Which of the following parameters affect burnout heat flux in the nucleate boiling region
(i) Heat of evaporation
(ii) Temperature difference
(iii) Density of vapor
(iv) Density of liquid
(v) Surface tension at the vapor-liquid interface
Mark the correct answer from the codes indicated below
(i) Heat of evaporation
(ii) Temperature difference
(iii) Density of vapor
(iv) Density of liquid
(v) Surface tension at the vapor-liquid interface
Mark the correct answer from the codes indicated below
a)
1, 2, 3 and 5
b)
1, 3, 4 and 5
c)
1, 2, 3 and 4
d)
1, 3 and 5
|
|
Baishali Roy answered |
Acc to Zuber relation, burn out (Q/A) = 0.18 p g h f g [p (p f – p g)/p g 2] 0.25 [p f/p g + p f] 0.5.
Consider the following statements regarding nucleate boiling
(i) The temperature of the surface is greater than the saturation temperature of the liquid
(ii) Bubbles are created by the expansion of entrapped gas oil vapor at small cavities in the surface
(iii) The temperature is greater than that in film boiling
(iv) The heat transfer from the surface to the liquid is greater than that in the film boiling
Which of these statements are correct?- a)1 and 3
- b)1, 2 and 4
- c)2, 3 and 4
- d)1, 2 and 3
Correct answer is option 'B'. Can you explain this answer?
Consider the following statements regarding nucleate boiling
(i) The temperature of the surface is greater than the saturation temperature of the liquid
(ii) Bubbles are created by the expansion of entrapped gas oil vapor at small cavities in the surface
(iii) The temperature is greater than that in film boiling
(iv) The heat transfer from the surface to the liquid is greater than that in the film boiling
Which of these statements are correct?
(i) The temperature of the surface is greater than the saturation temperature of the liquid
(ii) Bubbles are created by the expansion of entrapped gas oil vapor at small cavities in the surface
(iii) The temperature is greater than that in film boiling
(iv) The heat transfer from the surface to the liquid is greater than that in the film boiling
Which of these statements are correct?
a)
1 and 3
b)
1, 2 and 4
c)
2, 3 and 4
d)
1, 2 and 3
|
|
Rajveer Dasgupta answered |
The temperature must be less than that in film boiling.
The heat flux in nucleate boiling varies in accordance with- a)h f g
- b)(h f g) 0.5
- c)1/(h f g) 2
- d)(h f g) 3
Correct answer is option 'C'. Can you explain this answer?
The heat flux in nucleate boiling varies in accordance with
a)
h f g
b)
(h f g) 0.5
c)
1/(h f g) 2
d)
(h f g) 3
|
|
Dhruba Kapoor answered |
Q/A = δ f h f g [(p f – p g) g/σ] 0.5 [C f d t/h f g p C s f] 3.
The critical Reynolds number for transition from laminar to turbulent film condensation is- a)2000
- b)1900
- c)1800
- d)1700
Correct answer is option 'C'. Can you explain this answer?
The critical Reynolds number for transition from laminar to turbulent film condensation is
a)
2000
b)
1900
c)
1800
d)
1700
|
|
Aashna Datta answered |
This should be 1800 for perfect transition from laminar to turbulent film condensation.
Boiling refers to a change from the- a)Solid to a liquid phase
- b)Vapor to a liquid phase
- c)Liquid to a solid phase
- d)Liquid to a vapor phase
Correct answer is option 'D'. Can you explain this answer?
Boiling refers to a change from the
a)
Solid to a liquid phase
b)
Vapor to a liquid phase
c)
Liquid to a solid phase
d)
Liquid to a vapor phase
|
|
Niharika Kaur answered |
Boiling is a convective heat transfer process that is associated with change in the phase of a fluid.
With increase in excess temperature, the heat flux in boiling- a)Increases continuously
- b)Decreases and then increases
- c)Decreases, then increases and again decreases
- d)Increases, then decreases and again increases
Correct answer is option 'D'. Can you explain this answer?
With increase in excess temperature, the heat flux in boiling
a)
Increases continuously
b)
Decreases and then increases
c)
Decreases, then increases and again decreases
d)
Increases, then decreases and again increases
|
|
Rajveer Dasgupta answered |
It first increases to 50% then decreases not to zero and again increases to its maximum value.
Chapter doubts & questions for Boiling & Condensation - 6 Months Preparation for GATE Mechanical 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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