Refrigeration Questions and Answers – Effect of Various Parameters on VCR System – 1

This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Effect of Various Parameters on VCR System – 1”.

1. Which of these is not an effect of superheat in suction vapour?
a) increase in refrigeration effect
b) increase in compression work
c) decrease the capacity of compressor per ton of refrigeration
d) condenser size decreases

Explanation: The effects of superheat in suction vapour are increase in refrigeration effect, increase in compression work, decreasing the capacity of compressor per ton of refrigeration and increasing the condenser size as the heat rejected in the condenser increases.

2. The COP of the cycle may increase or decrease or remain unchanged depending upon the range of pressure and the degree of superheating.
a) True
b) False

Explanation: The COP of the cycle may increase or decrease or remain unchanged depending upon the range of pressure and the degree of superheating as it can affect the refrigeration effect, compression work, heat rejected in condenser etc. and thus the COP.

3. In which case will the refrigeration effect will not increase and the COP of cycle with superheated vapour in suction phase will be less than the COP of ideal cycle?
a) Superheating the vapour from state 1 to 1′
b) Superheating the vapour from state 1 to 2
c) Superheating the vapour from state 1′ to 2′
d) COP always increases when superheating vapour in suction vapour

Explanation: As we can see from the below picture of a cycle with superheated vapour in suction vapour, the refrigeration effect is not increased and thus the COP will be less than that of ideal COP.

4. Which one of the following is not effect of liquid sub cooling?
a) increase the refrigeration effect
b) reduce the piston displacement
c) increase the COP
d) increase the compressor power per ton of refrigeration

Explanation: Sub cooling the liquid reduces the compressor power per ton of refrigeration due to reduced mass flow rate of refrigerant. It also increases the refrigeration effect, reduce the piston displacement and increase the COP.

5. Which one of the following is not effect of change in suction pressure?
a) reduces the net refrigeration effect
b) reduces the mass flow rate of refrigerant per ton of refrigeration
c) reduces the COP
d) increases the compressor power per ton of refrigeration

Explanation: Change in suction pressure reduces the net refrigeration effect thus increasing the mass flow rate of refrigerant per ton of refrigeration.

6. Effect of high side pressure or discharge pressure or condenser pressure is to reduce the COP of the cycle.
a) True
b) False

Explanation: Effect of high side pressure or discharge pressure or condenser pressure is to reduce the COP of the cycle as the refrigeration effect is reduced and the compression work increases as well as the compressor power increases per ton of refrigeration due to increased mass flow and additional energy supplied in compression.

7. Heat rejected in the condenser increases by an amount equal to, when vapour in the suction vapour is superheated?

a) H2 – H2′
b) H2 + H2′
c) H2′ – H2
d) H2′ + H2

Explanation: As we see from the below diagram the heat rejected in the condenser increases by an amount equal to H2′ – H2.

Sanfoundry Global Education & Learning Series – Refrigeration & Air Conditioning.

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