Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning

36. 

Thermal conductivity of a material may be defined as the

A. quantity of heat flowing in one second through a slab of the material of area 1 cm2 and thickness 1 cm when its faces differ in temperature by 1° C
B. quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C
C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D. all of the above

Answer: Option D

Explanation:

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37. 

During sensible heating of air, specific humidity remains constant.

A. Agree
B. Disagree

Answer: Option A

Explanation:

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38. 

Air refrigeration cycle is used in

A. commercial refrigerators
B. domestic refrigerators
C. air-conditioning
D. gas liquefaction

Answer: Option D

Explanation:

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39. 

Reynolds number is the ratio of

A. energy transferred by convection to that by conduction
B. kinematic viscosity to thermal diffusivity
C. inertia force to viscous force
D. none of the above

Answer: Option C

Explanation:

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40. 

The wet bulb depression is zero when relative humidity is

A. zero
B. 0.5
C. 0.75
D. 1.0

Answer: Option D

Explanation:

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