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Heat Transfer

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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 Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

A perfect black body is one which

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

A perfect black body is one which Read More »

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning

The amount of radiation mainly depends upon the

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

The amount of radiation mainly depends upon the Read More »

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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 Read More »

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.

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning /
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.

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

Heat Transfer, Mechanical Engineering, Refrigeration and Air Conditioning