Heat Transfer

Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.

Question: A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.
[A].
True
[B].
False

Answer: Option A

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

Emissivity of a body will be equal to its absorptivity at all temperatures.

Question: Emissivity of a body will be equal to its absorptivity at all temperatures.
[A].
Yes
[B].
No

Answer: Option B

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called

Question: If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called
[A].
absorptive power
[B].
emissive power
[C].
emissivity
[D].
none of these

Answer: Option B

Explanation:

No answer description available for this question.

Read More If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called
Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

A perfect black body is one which

Question: A perfect black body is one which
[A].
is black in colour
[B].
absorbs heat radiations of all wave lengths falling on it
[C].
reflects all the heat radiations
[D].
transmits the heat radiations

Answer: Option B

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

The amount of radiation mainly depends upon the

Question: The amount of radiation mainly depends upon the
[A].
nature of the body
[B].
temperature of the body
[C].
type of surface of the body
[D].
all of these

Answer: Option D

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

Nusselt number (NN) is given by

Question: Nusselt number (NN) is given by
[A].

[B].

[C].

[D].

Answer: Option A

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

Question: In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
[A].
Reynold’s number
[B].
Grashoff’s number
[C].
Reynold’s number, Grashoff’s number
[D].
Prandtl number, Grashoff’s number

Answer: Option D

Explanation:

No answer description available for this question.

Read More In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

Question: In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in
[A].
parallel flow
[B].
counter flow
[C].
cross flow
[D].
all of these

Answer: Option D

Explanation:

No answer description available for this question.

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Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is

Question: A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is
[A].
20°C
[B].
40°C
[C].
60°C
[D].
66.7°C

Answer: Option A

Explanation:

No answer description available for this question.

Read More A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is
Heat Transfer | Mechanical Engineering | Refrigeration and Air Conditioning

For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference ™ for parallel flow is __________ that for counter flow.

Question: For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference ™ for parallel flow is __________ that for counter flow.
[A].
equal to
[B].
less than
[C].
greater than

Answer: Option A

Explanation:

No answer description available for this question.

Read More For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference ™ for parallel flow is __________ that for counter flow.