# Thermodynamics Questions and Answers – Multi-Stage Compression

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Multi-Stage Compression”.

1. For minimum work, the compression should be ____
b) isothermal
c) isochore
d) isobar

Explanation: This is the condition for minimum work.

2. The temperature after compression is given by
a) T2=(T1)(p2/p1)^(n/(n-1))
b) T2=(T1)(p2/p1)^((n+1)/n)
c) T2=(T1)(p2/p1)^((n-1)/n)
d) none of the mentioned

Explanation: Here T2 is the delivery temperature.

3. As the pressure ratio increases, delivery temperature ____
a) increases
b) decreases
c) remains constant
d) none of the mentioned

Explanation: This comes from the expression T2=(T1)(p2/p1)^((n-1)/n).

4. The volumetric efficiency ____ when carried out in stages.
a) decreases
b) increases
c) remains constant
d) none of the mentioned

Explanation: This is the reason why compression is carried out in stages.

5. The first stage of compression is done in ____ cylinder and next stage in ____ cylinder.
a) both in high pressure cylinder
b) both in low pressure cylinder
c) high pressure, low pressure
d) low pressure, high pressure

Explanation: This is how compression is carried out in two stages.

6. After passing through HP cylinder, the gas is passed to an intercooler.
a) true
b) false

Explanation: The gas is passed through an intercooler after it is compressed in LP cylinder.

7. In perfect intercooling, gas from intercooler has temperature equal to
a) inlet temperature
b) outlet temperature
c) intercooler temperature
d) all of the mentioned

Explanation: This is called complete or perfect intercooling when gas leaves the LP cylinder.

8. In perfect aftercooling, gas from intercooler has temperature equal to
a) inlet temperature
b) outlet temperature
c) intercooler temperature
d) all of the mentioned

Explanation: This is called complete or perfect aftercooling when gas leaves the HP cylinder.

9. The ideal intermediate pressure is given by
a) 2*p2/p1
b) sqrt(p2/p1)
c) (p1+p2)/2
d) sqrt(p1*p2)

Explanation: This is the ideal intermediate pressure for minimum work of compression.

10. The work required in HP compressor = work required in LP compressor.
a) true
b) false

Explanation: This happens when work of compression is minimum.

11. The intermediate pressure which produces minimum work also results in
a) equal discharge temperatures
b) equal work for two stages
c) equal pressure ratios in two stages
d) all of the mentioned

Explanation: These are the results when we consider minimum work of compression.

12. Which of the following is true for a multi-stage compression?
a) there is reduction in work required for each stroke
b) overall efficiency increases
c) cylinders can be adjusted according to size and strength
d) all of the mentioned

Explanation: These are few advantages of multi-stage compression.

13. Multi-cylinders give
a) less uniform torque
b) better mechanical balance
c) need large flywheel
d) all of the mentioned

Explanation: Multi-cylinders need smaller flywheel and give uniform torque.

14. In a multi-stage compression,
a) lubrication difficulties are reduced
b) explosion hazards are lessened
c) leakage losses are reduced
d) all of the mentioned 