Heat Transfer, Refrigeration and Air Conditioning MCQ
The process of ________ involves the movement or circulation of a mass or substance.
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Correct Answer:
Convection
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A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
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Correct Answer:
4 kW
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During humidification process, __________ increases.
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Correct Answer:
Relative humidity
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The relative humidity is defined as
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Correct Answer:
The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure
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The difference between dry bulb temperature and wet bulb temperature, is called
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Correct Answer:
Wet bulb depression
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A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
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Correct Answer:
All of these
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Thermal diffusivity is a
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Correct Answer:
Physical property of a substance
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The centrifugal compressors are generally used for refrigerants that require
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Correct Answer:
Large displacements and low condensing pressures
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In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively
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Correct Answer:
Ammonia and water
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According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)
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Correct Answer:
Pb = pa + pv
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During sensible cooling of air __________ decreases.
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Correct Answer:
Dry bulb temperature
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The water, alcohol and ammonia have same refrigerating effect at different altitudes.
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Correct Answer:
No
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In a refrigerating machine, heat rejected is __________ heat absorbed.
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Correct Answer:
Greater than
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The subcooling in a refrigeration cycle
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Correct Answer:
Increases C.O.P.
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In case of solids, the heat transfer takes place according to radiation.
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Correct Answer:
Incorrect
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Degree of saturation or percentage humidity is
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Correct Answer:
The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.
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An electrolux refrigerator is called a __________ absorption system.
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Correct Answer:
Three fluids
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The wet bulb temperature during sensible heating of air
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Correct Answer:
Increases
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The temperature of ammonia after compression in a vapour compression system is
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Correct Answer:
70 to 110° C
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The highest thermal diffusivity is of
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Correct Answer:
Lead
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The optimum effective temperature for human comfort is
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Correct Answer:
Lower in winter than in summer
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