Heat Transfer, Refrigeration and Air Conditioning – Section 2

31. Sulfur dioxide is extremely toxic and non-flammable.

A. True
B. False

Correct Answer: A. True

32. The transfer of heat from one body to another takes place only when there is a temperature difference between the bodies.

A. Yes
B. No

Correct Answer: A. Yes

33. A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

ht-se2-33

Correct Answer: Option D

34. Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)

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Correct Answer: Option A

35. Which of the following statement is correct for ammonia as a refrigerant?

A. It is toxic to mucous membranes.
B. it requires large displacement per TR compared to fluoro carbons.
C. It reacts with copper and its alloys.
D. all of these

Correct Answer: D. all of these

36. The wet bulb temperature at 100% relative humidity is __________ dew point temperature.

A. same as
B. lower than
C. higher than

Correct Answer: A. same as

37. The use of heat exchangers is made in

A. radiators in automobile
B. condensers and boilers in steam plants
C. condensers and evaporators in refrigeration and air conditioning units
D. all of the above

Correct Answer: D. all of the above

38. 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

Correct Answer: D. all of these

39. Which of the following statement is correct?

A. A grey body is one which absorbs all radiations incident on it.
B. At thermal equilibrium, the emissivity and absorptivity are same.
C. The energy absorbed by a body to the total energy falling on it is called emissivity.
D. A perfect body is one which is black in color

Correct Answer: B. At thermal equilibrium, the emissivity and absorptivity are same.

40. The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity.

A. Correct
B. Incorrect

Correct Answer: B. Incorrect

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