Chapter 15 Refrigeration Theory

Question 1

1. The liquid refrigerant Freon-12, subjected to atmospheric pressure (100.4 kPa abs,
   14.56 psi), boils at:
   A. -28°C (-18.4°F)
   B. -30°C (-22°F)
   C. -33°C (-27.4°F)
   D. -38°C (-36.4°F)
   E. -25°C (-13°F

Answer 1

B. -30°C (-22°F)

Question 2

2. How many tonnes of refrigeration would be accomplished if 251 244 kJ were
removed in one hour?
A. 12
B. 24
C. 16
D. 18
E. 20

Answer 2

D. 18

Question 3

3. How many tonnes of refrigeration would be accomplished if 251 244 kJ were
removed in 24 hours?
A. 0.75
B. 2.4
C. 1.8
D. 10
E. 1

Answer 3

A. 0.75

Question 4

4. One tonne of refrigeration is equal to the equivalent of the heat needed to:
   A. Melt 1 tonne (1000 kg) of ice at a temperature of 0°C in 12 hours
   B. Melt 1 tonne (1000 kg) of ice at a temperature of 0°C in 24 hours
   C. Melt ½ tonne (500 kg) of ice at a temperature of 0°C in 24 hours
   D. Melt 1 tonne (1000 kg) of ice at a temperature of 10°C in 24 hours
   E. Melt 1 tonne (1000 kg) of ice at a temperature of 100°C in 24 hours

Answer 4

B. Melt 1 tonne (1000 kg) of ice at a temperature of 0°C in 24 hours

Question 5

5. The low pressure in the evaporator is maintained by the:
A. Condenser
B. Expansion valve
C. Chiller
D. Receiver
E. Compressor

Answer 5

E. Compressor

Question 6

6. The heat transfer process that ice undergoes in an ice box is \_\_\_\_\_.
A. Latent heat gain
B. Sensible heat gain
C. Superheating
D. Sub-cooling
E. Latent heat los

Answer 6

A. Latent heat gain

Question 7

7. The compression ratio is calculated by dividing the:
   A. Discharge gauge pressure by the Suction gauge pressure
   B. Absolute discharge pressure by the suction gauge pressure
   C. Discharge gauge pressure by the absolute suction pressure
   D. Absolute discharge pressure by the absolute suction pressure
   E. Absolute suction pressure by the absolute discharge pressure

Answer 7

D. Absolute discharge pressure by the absolute suction pressure

Question 8

8. The refrigeration process involves the transfer of heat from the substance to be
   cooled to a lower temperature substance called the:
   A. Condensate
   B. Regenerant
   C. Refraction
   D. Refrigerant
   E. Evaporation

Answer 8

D. Refrigerant

Question 9

9. The boiling point of water is 100°C (212°F) when atmospheric pressure is 101.325
kPa (14.7 psi) and is also known as the:
A. Saturation temperature
B. Condensation temperature
C. Vapour pressure
D. Vapour temperature
E. Enthalpy temperature

Answer 9

A. Saturation temperature

Question 10

10.The boiling point of a liquid is raised by _____.
A. Increasing the strength of the refrigerant
B. Increasing the pressure on the refrigerant
C. Increasing the temperature of the refrigerant
D. Increasing the size of the expansion valve
E. Decreasing the pressure on the refrigerant

Answer 10

B. Increasing the pressure on the refrigerant

Question 11

11.Refrigeration is defined as the thermodynamic process of:
A. Lowering the temperature of a substance below the temperature of its
surroundings
B. Lowering the pressure of a substance below the temperature of its surroundings
and maintaining this substance at the lower temperature
C. Lowering the temperature of a substance below the temperature of its
surroundings and maintaining this substance at the lower temperature
D. Lowering the pressure of a substance below the pressure of its surroundings and
maintaining this substance at the lower pressure
E. Lowering the temperature of a substance below the pressure of its surroundings
and maintaining this substance at the lower pressure

Answer 11

B. Lowering the pressure of a substance below the temperature of its surroundings
and maintaining this substance at the lower temperature

Question 12

12.The control valve regulates the flow of liquid refrigerant into the:
A. Condenser
B. Expansion valve
C. Evaporator
D. Compressor
E. Receiver

Answer 12

C. Evaporator

Question 13

13.The high pressure in the condenser is maintained by the:
A. Compressor
B. Expansion valve
C. Evaporator
D. Receiver
E. Chiller

Answer 13

A. Compressor

Question 14

14.The coefficient of performance is the ratio of the amount of heat absorbed from the
refrigerated medium by the __________ to the amount of __________________:
A. Compressor; energy used to drive the evaporator
B. Condenser; energy used to drive the compressor
C. Evaporator; energy used to drive the compressor
D. Condenser; energy released in the evaporator
E. Evaporator; energy used in the condenser

Answer 14

C. Evaporator; energy used to drive the compressor

Question 15

15.After leaving the compressor as a high-pressure vapour, the refrigerant can be
exposed to air or water temperatures in a heat exchanger, called a:
A. Cooler
B. Chiller
C. Evaporator
D. Condenser
E. Receiver

Answer 15

D. Condenser