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.

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.

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.

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.

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.

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

[B].

[C].

[D].

Answer: Option A

Explanation:

No answer description available for this question.

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.

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.

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.

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.