250+ TOP MCQs on Two/Multi Stage Compression with Liquid Intercooling and Answers

Refrigeration Multiple Choice Questions on “Two/Multi Stage Compression with Liquid Intercooling”.

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1. Which one of the following is not an advantage of compound vapor compression with intercooler?
a) It improves the volumetric efficiency for the given pressure ratio
b) It reduces the leakage losses
c) It provides effective lubrication
d) It does not give a uniform torque

Answer: d
Clarification: One of the advantages of compound vapor compression with intercooler is that it gives more uniform torque, and hence a smaller size flywheel is needed. Some other advantages are that it improves the volumetric efficiency for the given pressure ratio, it reduces the leakage losses, it provides effective lubrication, etc.

2. The refrigeration effect produced by a system is 10 TR and work done by the low-pressure compressor, and high-pressure compressor is 3 and 4 kW respectively. What is the value of C.O.P. for the given conditions?
a) 8.75
b) 11.67
c) 3.5
d) 5

Answer: d
Clarification: Given: R.E. = 10 TR = 10 x 3.5 = 35 kW
Low-pressure compressor work, W_L = 3 kW
High-pressure compressor work, W_H = 4 kW
C.O.P. = R.E. / Total Work
= R.E. / W_L + W_H
= 35 / (3 + 4)
= 35 / 7
= 5.

3. Liquid refrigerant is used for inter cooling commonly in multi stage ammonia plants.
a) True
b) False

Answer: a
Clarification: Liquid refrigerant is used for inter cooling commonly in multi stage ammonia plants, because of less power requirements due to the fact that the mass of liquid evaporated during intercooling is extremely small because of its latent heat of vaporization and the constant entropy lines of ammonia becomes very flat in the superheat region.

4. Liquid refrigerant is not used for inter cooling in multi stage R- 12 plants.
a) True
b) False

Answer: a
Clarification: In case of R – 12 refrigerants, when liquid refrigerant is used for intercooling the total power requirement may increase. It is due to the fact that latent heat of vaporization is small and the constant entropy lines do not change very much with temperature.

5. A compound vapour compression with an intercooler system is used to take 10 TR of refrigeration load (Q). The power required for the refrigerating system P is 550 KW. What is its COP?
a) 0.078
b) 0.086
c) 0.063
d) 0.089

Answer: c
Clarification: COP = (frac{210×Q}{P×60})
COP = (frac{210×10}{550×60})
= 0.063.

6. Which of the following is not a disadvantage of multiple compressions with intercooling between the stages?
a) Increases the initial cost
b) Size of plant increases
c) Increases the maintenance cost
d) Cylinder wall thickness of low pressure cylinder is increased

Answer: d
Clarification: The cylinder wall thickness of low pressure cylinder is reduced, since it is designed to withstand low pressure only. It reduces the cost of the compressor.

7. Why intercooling by liquid refrigerant never used in R-12 systems?
a) High latent heat of vaporization
b) Low latent heat of vaporization
c) Medium latent heat of vaporization
d) High toxicity

Answer: b
Clarification: In the case of refrigerant R-12, power requirements may increase. Due to the low latent heat of vaporization and constant entropy lines not getting affected by temperature, the increased mass flow rate of refrigerant through the high-pressure compressor is not compensated by saving in work done close to the saturated vapor line. This might result in a high power requirement and decreasing the C.O.P. Hence, intercooling by the liquid refrigerant in R-12 systems is never employed.