250+ TOP MCQs on Units of Refrigeration – 2 and Answers

Refrigeration Interview Questions on “Units of Refrigeration – 2”.

1. What are the pressure in the places at “a” and “b” respectively in the given graph?

a) Gauge, Absolute
b) Absolute, Gauge
c) Atmospheric, Gauge
d) Gauge, Atmospheric
Answer: d
Clarification: Absolute pressure is the sum of Gauge pressure and Atmospheric pressure. Also, Atmospheric pressure is measured from the datum level and Gauge pressure starts above the Atmospheric pressure.

2. What does 1 Tonne (TR) in refrigeration mean?
a) Weight of gases
b) Weight of coolant
c) Capacity of 1 tonne air to be cooled to 0 C in 24 hours
d) Capacity of 1 tonne water to be cooled to 0 C in 24 hours
Answer: d
Clarification: 1 Tonne Rating (TR) means that the capacity is such that it can convert 1 tonne of water to ice i.e. 0C in 24 hours.

3. 1 Tonne = ______ KJ/s.
a) 2.67
b) 1.087
c) 3.5
d) 232.6
Answer: c
Clarification: 1TR = 1000 × 335 KJ in 24 hours
= (frac{1000 × 335}{24 × 60}) KJ/min
= 232.6 KJ/min = 210 KJ/min (practically taken)
= 3.5 KJ/s.

4. Which is the S.I. unit to measure pressure in refrigeration?
a) Newton
b) Joule
c) Pascal
d) Bar
Answer: c
Clarification: Generally, unit like N/mm², N/m², KN/mm² and MN/mm² etc. are used but the S.I. unit used is N/m² i.e. Pascal.

5. 0 Kelvin = ____ Celsius.
a) -273 C
b) 273 C
c) -273 K
d) 0 C
Answer: a
Clarification: As for Temperature 273 K= 0 C, i.e. 0 K = -273 C from the temperature scale developed by Celsius.

6. The heat removing capacity of one tonne refrigeration is equal to?
a) 210 KJ/min
b) 620 KJ/min
c) 240 KJ/min
d) 430 KJ/min
Answer: a
Clarification: 1TR = 1000 kg × 335 KJ (Latent heat of Ice) in 24 hours
= (frac{1000 × 335}{24 × 60}) KJ/min
= 232.6 KJ/min
= 210 KJ/min (practically taken).

7. What does 35 Celsius (C) mean on Kelvin scale (K)?
a) 350
b) 135
c) 308
d) 298
Answer: c
Clarification: For conversion of a unit from Celsius to Kelvin, 273 is to added, i.e. 35 + 273 = 308 K (here).

8. What is S.I. unit of refrigeration?
a) J/min
b) KJ/s
c) KWh
d) Kg/s
Answer: b
Clarification: KJ/s or KW is the S.I. unit of refrigeration, which is converted to Tonnes as commercial unit.

9. 1 N/mm² = _____ mm of Hg (mercury).
a) 1
b) 256
c) 760
d) 720
Answer: c
Clarification: 1 N/mm² is also called 1 Pascal which is a measure of pressure. Hence to measure 1 Pascal of pressure the height of mercury found out practically was 760 mm. So 1 N/mm² = 760 mm of Hg.

10. What is the S.I. unit required to measure the work done in refrigeration is?
a) Joule/kg
b) KJ/kg
c) Joule/m. s
d) Joule/s
Answer: d
Clarification: The S.I. unit of Work done is Watt, i.e. Joule/Second. That means the amount of energy required in joules for unit time.