Book 2 Chapter 15: Refrigeration Theory

Question 1

The boiling point of a liquid is raised by _____________.
A) Increasing the pressure of the refrigerant
B) Increasing the strength of the refrigerant
C) Increasing the temperature of the refrigerant
D) Increasing the size of the expansion valve

Answer 1

A) Increasing the pressure of the refrigerant

Question 2

The heat transfer process that ice undergoes in an ice box is _______________.
A) Sensible heat
B) Latent heat
C) Superheating
D) Sub-cooling

Answer 2

B) Latent heat

Question 3

Which value below is correct for 1 tonne of refrigeration?
A) 335,000 kJ per 24 hours
B) 13,958 kJ/h
C) 3.88 kJ/s
D) All of the above

Answer 3

D) All of the above

Question 4

How many tons of refrigeration would be accomplished if 251,244 kJ were removed in one hour?
A) 12.2
B) 24.5
C) 19.8
D) 16.7

Answer 4

C) 19.8

Question 5

The net refrigerating effect of a refrigerant is the amount of heat:
A) Absorbed by the refrigerant in the evaporator
B) Absorbed by the refrigerant in the condenser
C) Discharged by the refrigerant in the evaporator
D) Discharged by the condenser
E) Absorbed by the evaporator

Answer 5

A) Absorbed by the refrigerant in the evaporator

Question 6

Heat, that causes a drop in temperature when removed, is called _______ heat:
A) Convective
B) Radiant
C) Conductive
D) Latent
E) Sensible

Answer 6

E) Sensible

Question 7

How many kilowatt-hours will a 24 tonne refrigeration system use in 24 hours?
A) 232.8
B) 8,040,000
C) 4732
D) 2233
E) 13,958

Answer 7

D) 2233

Question 8

The pressure ratio of the refrigeration system is calculated by dividing the:
A) Absolute condenser pressure by the absolute evaporator pressure
B) System volume by the cylinder volume
C) Absolute suction pressure by the absolute discharge pressure
D) Suction pressure by the discharge pressure
E) Discharge pressure by the suction pressure

Answer 8

E) Discharge pressure by the suction pressure

Question 9

In the case of a simple ice box which of the following heat transfers is correct?
A) Air gives up latent heat; ice does not gain any heat
B) Air gives up sensible heat; ice does not gain any heat
C) Air gives up sensible heat; ice gains sensible heat
D) Air gives up latent heat; ice gains latent heat
E) Air gives up sensible heat; ice gains latent heat

Answer 9

E) Air gives up sensible heat; ice gains latent heat

Question 10

In a compression refrigeration system, the evaporator:
A) Is used to dry the refrigerant
B) Is where the refrigerant is condensed
C) Is cooled by the air
D) Increases the refrigerant pressure
E) Is in the cooled space

Answer 10

E) Is in the cooled space

Question 11

Capacity and performance calculations are performed by means of:
A) Steam tables
B) Refrigerant tables
C) Actuarial tables
D) Trigonometric tables
E) Psychometric charts

Answer 11

B) Refrigerant tables

Question 12

Temperature control in a refrigerant system is accomplished by:
A) Increasing refrigerant flow
B) Changing refrigerants
C) Regulating the pressure in the evaporator
D) Increasing compressor speed
E) Increasing water flow to the condenser

Answer 12

C) Regulating the pressure in the evaporator

Question 13

Refrigeration is possible because of a refrigerant’s capacity to transfer:
A) Radiant heat
B) Cold
C) Latent heat
D) Mechanical heat
E) Electrical heat

Answer 13

C) Latent heat

Question 14

The rate at which a system will remove heat from the refrigerated medium is defined as:
A) Net refrigerating effect
B) Compression Ratio
C) Refrigeration capacity
D) Differential efficiency
E) Coefficient of Performance

Answer 14

C) Refrigeration capacity

Question 15

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

Answer 15

A) Condenser

Question 16

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

Answer 16

C) Saturation temperature

Question 17

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

Answer 17

B) Increasing the pressure on the refrigerant

Question 18

The coefficient of performance is the ratio of the amount of heat absorbed from the refrigerated medium by the _________ to the amount of ____________.
A) Condenser, energy used to drive the compressor
B) Condenser, energy released in the evaporator
C) Compressor, energy used to drive the evaporator
D) Evaporator, energy used in the condenser
E) Evaporator, energy to drive the compressor

Answer 18

E) Evaporator, energy to drive the compressor

Question 19

The heat transfer process that ice undergoes in an ice box is _________.
A) Superheating
B) Latent heat gain
C) Sensible heat gain
D) Latent heat loss
E) Sub-cooling

Answer 19

B) Latent heat gain

Question 20

One tonne of refrigeration is equal to the equivalent of the heat needed to:
A) Melt 1 tonne (1000kg) of ice at a temperature of 10ºC in 24 hours
B) Melt 1 tonne (1000kg) of ice at a temperature of 0ºC in 12 hours
C) Melt 1 tonne (1000kg) of ice at a temperature of 0ºC in 24 hours
D) Melt 1 tonne (1000kg) of ice at a temperature of 100ºC in 24 hours
E) Melt 1/2 tonne (5000kg) of ice at a temperature of 0ºC in 24 hours

Answer 20

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

Question 21

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

Answer 21

B) Compressor

Question 22

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

Answer 22

D) Lowering the temperature of a substance below the temperature of its surroundings and maintain this substance at the lower temperature

Question 23

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

Answer 23

C) Absolute discharge pressure by the absolute suction pressure

Question 24

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

Answer 24

C) Compressor