Questions and answers for exam Preparation

MCQs

Total Questions : 1342 | Page 8 of 135 pages

Question 71. If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be

Discuss Question

Answer: Option D. -> 6

Question 72. Vertical lines on pressure-enthalpy chart show constant

Pressure lines
Temperature lines
Total heat lines
Entropy lines

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Answer: Option C. -> Total heat lines

Question 73. A vapour absorption refrigerator uses _________ as a refrigerant.

Water
Ammonia
Freon
Aqua-ammonia

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Answer: Option D. -> Aqua-ammonia

Question 74. Which of the following statement is correct for ammonia as a refrigerant?

It is toxic to mucous membranes.
It requires large displacement per TR compared to fluoro carbons.
It reacts with copper and its alloys.
All of these

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Answer: Option D. -> All of these

Question 75. In vapour compression refrigeration system, refrigerant occurs as liquid between

Condenser and expansion valve
Compressor and evaporator
Expansion valve and evaporator
Compressor and condenser

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Answer: Option C. -> Expansion valve and evaporator

Question 76. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called

Kinetic theory of gases
Newton's law of gases
Dalton's law of partial pressures
Avogadro's hypothesis

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Answer: Option C. -> Dalton's law of partial pressures

Question 77. Which of the following statement is wrong?

The value of C.O.P. is always greater than one
In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour
The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region
None of the above

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Answer: Option D. -> None of the above

Question 78. Which of the following statement is wrong?

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.
In vapour compression cycle, the useful part of the heat transfer is at the condenser.
In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.
The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.

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Answer: Option D. -> The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.

Question 79. In S.J. unit, one ton of refrigeration is equal to