250+ MCQs on Two/Multi Stage Compression with Water Intercooling, Liquid Subcooling and Flash Chamber

Refrigeration Multiple Choice Questions on “Two/Multi Stage Compression with Water Intercooling, Liquid Subcooling and Flash Chamber – 1”.

1. The heat taken and given by the flash chamber is same.
a) True
b) False

Answer: a
Clarification: The heat taken and given by the flash chamber is same as the flash chamber is an insulated vessel; hence there is no heat exchange between the flash chamber and the atmosphere.

2. What is the value of Refrigeration effect if m₂ = 2 kg/min, m₃ = 0.8 kg/min and enthalpies for the refrigerant at saturated vapor and saturated liquid line are 1420 and 1260 kJ/kg?
a) 192
b) 194
c) 196
d) 129

Answer: a
Clarification: Given: m₂ = 2 kg/min
m₃ = 0.8 kg/min
h₁ = 1420 kJ/kg and h_f10 = h₁₁ = 1260 kJ/kg
As, m₁ = m₂ – m₃
= 2 – 0.8
= 1.2
Refrigeration effect = m₁ (h₁ – h₁₁)
= 1.2 (1420 – 1260)
= 1.2 x 160
= 192 kJ/min.

3. Find the coefficient of performance when the refrigeration effect (Re) is 145.7 and the work done (W) is 32.46 KJ.
a) 4.5
b) 5.5
c) 4.6
d) 5.6

Answer: a
Clarification: COP = (frac{210×Q}{W})
COP = (frac{Re}{W} = frac{145.7}{32.46})
= 4.5.

4. By using flash chambers the total work done per kg of refrigerant is reduced.
a) True
b) False

Answer: a
Clarification: By using flash chambers the total work done per kg of refrigerant is reduced as the refrigerant can be expanded close to the liquid line and hence work done per kg reduces.

5. Which one of the following is not an advantage of water intercooling when used in a multi stage compression?
a) Reduces the work to be done in high pressure
b) Reduces the specific volume of the refrigerant
c) Requires a compressor of more stroke volume
d) Requires a compressor of less stroke volume

Answer: c
Clarification: When water intercooling is used in a multi stage compression the work to be done in high pressure is reduced, the specific volume of the refrigerant is reduced and a compressor of less stroke volume is required.