# 250+ TOP MCQs on Theoretical VCR with Dry Saturated Vapour after Compression – 1 and Answers

Refrigeration Multiple Choice Questions on “Theoretical VCR with Dry Saturated Vapour after Compression – 1”.

1. In vapor compression cycle having dry saturated vapor at the end of compression the work done is given by?

H2 – Enthalpy of vapor after compression
H1 – Enthalpy of vapor before compression
a) H2 – H1
b) H2 + H1
c) H2 × H1
d) H2 ÷ H1
Clarification: Work is done on the compressor in the compression process (1 – 2), and the external work-done in the remainder process of the cycle is zero. Hence the net work-done equals to the compressor work.

2. In vapor compression cycle having dry saturated vapor at the end of compression the refrigeration effect is given by?

H1 – Enthalpy of vapor before compression
H4 – Enthalpy of vapor before entering evaporator
H2 – Enthalpy of vapor after compression
a) H1 – H4
b) H2 – H4
c) H1 × H4
d) H2 × H4
Clarification: Refrigeration effect is the heat absorbed by the vaporizing refrigerant in the evaporator during the process (4 – 1), therefore refrigeration effect = H1 – H4.

3. The COP of vapor compression having vapor as dry saturated after compression having refrigeration effect (Re) of 58.84 and work done (W) of 17.95 is ________
a) 3.278
b) 4.39
c) 4.234
d) 3.865
Clarification: The COP is given by Refrigeration effect by work done,
COP=(frac{Re}{W})
=(frac{58.84}{17.95})=3.278.

4. Entropy of dry-saturated vapor when Sf is 0.2513 and Sfg is 4.7878, is _______
Sf – Entropy of saturated liquid at pressure p
Sfg – Entropy change during vaporization
a) 6.987
b) 5.987
c) 5.0391
d) 4.776
Clarification: Entropy of dry-saturated vapor when Sf is 0.2513 and Sfg is 4.5819, is given by
Sg = Sf + Sfg = 0.2513+4.7878 = 5.0391.

5. One of the assumptions of the vapor compression cycle is that all of the processes are reversible.
a) True
b) False
Clarification: Vapor compression cycle with vapor being dry saturated after compression is a theoretical cycle having various assumptions. One of the assumptions is that all the processes are reversible.

6. In which case does the compression process remains in superheated state?
a) Wet state
b) Dry state
c) Semi-dry state
d) Always
Clarification: In case of dry state the compression process remains in superheated state i.e. for compression of dry-saturated vapor or superheated vapor.

7. Dry compression is preferred over wet compression.
a) True
b) False