Heat Transfer, Refrigeration and Air Conditioning – Section 1

31. While designing the refrigeration system of an aircraft, the prime consideration is that the

A. system has high C.O.P.
B. power per TR is low
C. mass of refrigerant circulated in the system is low
D. mass of the refrigeration equipment is low

Correct Answer: D. mass of the refrigeration equipment is low

32. The heat transfer takes place according to

A. Zeroth law of thermodynamics
B. First law of thermodynamics
C. Second law of thermodynamics
D. Kirchhoff’s law

Correct Answer: C. Second law of thermodynamics

33. An Electrolux refrigerator is called a __________ absorption system.

A. single fluid
B. two fluids
C. three fluids

Correct Answer: C. three fluids

34. The heat transfer by radiation __________ a medium.

A. requires
B. does not require

Correct Answer: B. does not require

35. Thermal conductivity of water __________ with rise in temperature.

A. remains same
B. decreases
C. increases
D. may increase or decrease depending upon the temperature

Correct Answer: D. may increase or decrease depending upon the temperature

36. During adiabatic saturation process on unsaturated air __________ remains constant.

A. relative humidity
B. dew point temperature
C. dry bulb temperature
D. wet bulb temperature

Correct Answer: D. wet bulb temperature

37. The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

A. equal to one
B. greater than one
C. less than one
D. equal to Nusselt number

Correct Answer: A. equal to one

38. A perfect black body is one which

A. is black in color
B. absorbs heat radiations of all wavelengths falling on it
C. reflects all the heat radiations
D. transmits the heat radiations

Correct Answer: B. absorbs heat radiations of all wavelengths falling on it

39. Degree of saturation or percentage humidity is

A. the mass of water vapor present in 1 m3 of dry air
B. the mass of water vapor present in 1 kg of dry air
C. the ratio of the actual mass of water vapor in a unit mass of dry air to the mass of water vapor in the same mass of dry air when it is saturated at the same temperature and pressure.
D. the ratio of the actual mass of water vapor in a given volume of moist air to the mass of water vapor in the same volume of saturated air at the same temperature and pressure

Correct Answer: C. the ratio of the actual mass of water vapor in a unit mass of dry air to the mass of water vapor in the same mass of dry air when it is saturated at the same temperature and pressure.

40. The coefficient of performance of Heat Pump is always __________ one.

A. equal to
B. less than
C. greater than

Correct Answer: C. greater than

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