Refrigeration Units 113,114 & 115

Question 1

In the case of a simple ice box which of the following heat transfers is correct?

a) Air loses latent heat, ice does not gain any heat.
b) Air loses sensible heat, ice does not gain any heat. c) Air loses sensible heat, ice gains sensible heat.
d) Air loses sensible heat, ice gains latent heat.
e) Air loses latent heat, ice gains latent heat

Answer 1

d) Air loses sensible heat, ice gains latent heat.

Question 2

Which of the following is an example of a loss of latent heat?

i) water evaporating
ii) ice melting
iii) refrigerant evaporating
iv) air cooling

a) iv only
b) iii only
c) i, iii, and iv
d) both i and iii
e) none of the above

Answer 2

e) none of the above

Question 3

The function of the condenser is to

a) vaporize the liquid refrigerant
b) change high pressure refrigerant vapour to liquid
c) pressurize low pressure refrigerant vapour
d) vent off vaporized refrigerant
e) lower the liquid refrigerant pressure

Answer 3

b) change high pressure refrigerant vapour to liquid

Question 4

Which of the following statements about low-side pressure and temperature is false?

a) The evaporation temperature of the refrigerant should be 5 - 10 degrees C higher than that of the cooled medium.
b) For a given amount of heat transfer an oversized evaporator can be operated at a higher temperature. c) The low side pressure depends on the type of evaporation used.
d) The evaporation temperature of the refrigerant will be higher if the evaporator lowers the refrigerant pressure.
e) All of the above.

Answer 4

a) The evaporation temperature of the refrigerant should be 5 - 10 degrees C higher than that of the cooled medium

Question 5

Which of the following statements about high-side pressure and temperature is true?

a) The heat flow is from the cooling medium to the hot refrigerant.
b) The condensing temperature of the vapour is 15 - 20 degrees C higher than the temperature of the medium used in the condenser.
c) The condensation temperature of the refrigerant will be lower if the pressure of the vapourized refrigerant is lowered.
d) The condenser functions by taking latent heat from the surrounding air and adding it as sensible heat to the refrigerant.
e) None of the above

Answer 5

b) The condensing temperature of the vapour is 15 - 20 degrees C higher than the temperature of the medium used in the condenser.

Question 6

The rate at which a system will remove heat from the refrigerated medium is defined as

a) coefficient of performance
b) net refrigerating effect
c) refrigeration capacity
d) compression ratio
e) differential efficiency

Answer 6

c) refrigeration capacity

Question 7

Refrigerant mediums will evaporate

a) when pressure is increased
b) when temperature is increased
c) when they are diluted
d) when temperature is decreased
e) when heat is removed

Answer 7

b) when temperature is increased

Question 8

One tonne of refrigeration is

a) 13958 kJ per day
b) 100 kJ per minute
c) 233 kJ per minute
d) 13958 J per hour
e) 335 J per second

Answer 8

c) 233 kJ per minute

Question 9

If a cooled medium had an evaporation temperature of 2 degrees C, the evaporation temperature of the liquid refrigerant should be approximately

a) 2 degrees C
b) 6 - 8 degrees C
c) 1 degree C
d) 0 degrees C
e) -8 to -3 degrees C

Answer 9

e) -8 to -3 degrees C

Question 10

Which column in the refrigerant table lists the absolute pressure in kPa?

a) Column 1
b) Column 2
c) Column 3
d) Column 4
e) None of the above

Answer 10

b) Column 2

Question 11

Which of the following characteristics is common in all of the group B refrigerants?

a) High toxicity
b) High flammability
c) Average Flammability
d) Low Toxicity

Answer 11

a) High toxicity

Question 12

R-22 (Freon-22) is nontoxic and nonflammable. Which group does it belong to?

a) Group A2
b) Group B4
c) Group A1
d) Group A3
e) Group B

Answer 12

c) Group A1

Question 13

What is the name of the refrigerant that has the following characteristics? It is nonflammable, odourless, nontoxic, it does not have a corrosive effect on metal if water is present and at atmospheric pressure it has a boiling point of -40.6 degrees C.

a) Ammonia
b) Freon-22
c) Sulphur Dioxide
d) Butane
e) Propane

Answer 13

b) Freon-22

Question 14

The ideal commercial refrigerant should

a) have a low latent heat capacity
b) have a high boiling point
c) have high condensing pressure
d) be environmentally friendly
e) be the least costly

Answer 14

d) be environmentally friendly

Question 15

Ammonia refrigerants

a) have high sensible heat capacity
b) mix well with oil
c) are very expensive
d) are well suited for industrial refrigeration
e) are ideally suited to copper piping system

Answer 15

d) are well suited for industrial refrigeration

Question 16

The refrigerant R-11 belongs to the following group

a) group “A2”
b) group “B1”
c) group “A3
d) group “2B”
e) group “A1”

Answer 16

e) group “A1”

Question 17

Which of the following is a thermodynamic property of heat?

a) entropy
b) enthalpy
c) density
d) volume
e) all of the above

Answer 17

e) all of the above

Question 18

The property which has to be known for the calculation of the size of control valve and piping etc, is

a) specific volume
b) enthalpy
c) refrigerating effect
d) density
e) boiling point

Answer 18

d) density

Question 19

The refrigerating effect of a refrigerant is

a) equal to its latent heat of vaporization
b) greater than its latent heat of vaporization
c) less than its latent heat of vaporization
d) equal to its specific heat capacity
e) equal to its specific volume

Answer 19

a) equal to its latent heat of vaporization

Question 20

The standard refrigeration cycle is used to compare refrigerants and machines operating under comparable conditions. These standard conditions are:

a) 1030 kPa and atmospheric pressure
b) 30 degrees Celsius condensing and -15 degrees Celsius evaporating
c) 30 kPa and atmospheric pressure
d) -30 degrees Celsius condensing and 15 degrees Celsius evaporating
e) 30 kPa and atmospheric temperature

Answer 20

b) 30 degrees Celsius condensing and -15 degrees Celsius evaporating

Question 21

The latent heat of fusion of ice

a) is the sensible heat required to melt ice
b) is 335 kJ per 1 kg
c) is 335 kJ per 1 ton
d) is the latent heat required to evaporate ice
e) is 4.2 kJ per gram

Answer 21

b) is 335 kJ per 1 kg

Question 22

The ability of a refrigerant to be dissolved into oil and vice versa is called

a) moisture reaction
b) enthalpy
c) density
d) leakage tendency
e) miscibility

Answer 22

e) miscibility

Question 23

Which of the following is not a physical property of refrigerants?

a) Toxicity
b) Odour
c) Leakage tendency
d) Density
e) Explosiveness

Answer 23

d) Density

Question 24

Ammonia is the only commonly used refrigerant which has the physical property of

a) miscibility
b) enthalpy
c) flammability
d) density
e) low condensing pressure

Answer 24

c) flammability

Question 25

Molecular mass is a dependent factor in which of the following physical properties?

a) miscibility
b) leakage tendency
c) toxicity
d) flammability
e) explosivenes

Answer 25

b) leakage tendency

Question 26

Freon 22 refrigerant

a) is not miscible with oil
b) is mostly used in packing plants
c) is corrosive on copper
d) is corrosive on aluminum
e) is a heat transferring medium

Answer 26

e) is a heat transferring medium

Question 27

Which of the following are principal parts in a closed cycle compression refrigeration system?

i) Absorber
ii) Evaporator
iii) Compressor
iv) Condenser

a) both i and ii
b) iii only
c) i, ii, iv
d) ii, iii, iv
e) i, ii, iii

Answer 27

d) ii, iii, iv

Question 28

Raising the condensing point (saturation temperature) of the refrigerant vapour above the temperature of the cooling medium is the function of the

a) compressor
b) condenser
c) evaporator
d) absorber
e) refrigerant

Answer 28

a) compressor

Question 29

Which of the following is NOT a component of the low pressure side of the system?

a) compressor discharge
b) evaporator
c) downstream side of the regulating valve
d) medium to be cooled
e) all of the above

Answer 29

a) compressor discharge

Question 30

The temperature in the evaporator

a) depends on pressure in the receiver
b) will decrease when the compressor stops
c) depends on the pressure in the evaporator
d) depends on the ambient temperature
e) is controlled by the charging valve

Answer 30

c) depends on the pressure in the evaporator

Question 31

A purpose of a liquid refrigerant control or regulating valve is

a) to drain the receiver
b) to regulate the refrigerant flow to the evaporator
c) to maintain a constant level in the receiver
d) to regulate the cooling water to condenser
e) to isolate the high side from the low side

Answer 31

b) to regulate the refrigerant flow to the evaporator

Question 32

Refrigerant condensers

a) are always water cooled
b) cool the gas refrigerant discharged from the compressor
c) have a safety valve
d) remove sensible heat only from the refrigerant
e) are not required for freon type refrigerants

Answer 32

b) cool the gas refrigerant discharged from the compressor

Question 33

For a direct expansion system which of the following statements is true?

a) The evaporator in this system is never in direct contact with the material or space being refrigerated. b) For large systems calcium chloride brine is cooled by the evaporator then pumped to the area being refrigerated.
c) Water cooled by the chiller evaporation coils is used to refrigerate at temperatures below 0 degrees C.
d) The evaporator can be located in air circulating ducts communicating with the material or space being refrigerated.
e) Water cooled by the chiller evaporation coils is

Answer 33

d) The evaporator can be located in air circulating ducts communicating with the material or space being refrigerated.

Question 34

The primary difference between direct and indirect refrigeration systems is the

a) type of heat transfer medium
b) type of refrigerant
c) evaporator pressure
d) compressor location
e) evaporator location

Answer 34

e) evaporator location

Question 35

Which of the following statements about a system that circulates warm brine or water back to a chiller tank is true?

a) The system is a direct refrigeration system.
b) The evaporator in the system is located in direct contact with the material being refrigerated.
c) The brine or water is the refrigerant.
d) The evaporator cools the brine or water.
e) All of the above.

Answer 35

d) The evaporator cools the brine or water.

Question 36

The type of brine used for skating and hockey rink refrigeration systems is usually

a) calcium sulphate
b) calcium chloride
c) calcium carbide
d) calcium nitrate
e) sodium chloride

Answer 36

b) calcium chloride

Question 37

Refrigerant evaporators

a) always have the refrigerant on the shell side
b) are located between the expansion valve and the receiver
c) may have brine pumped past the coils in an indirect system
d) may be of the walk-in type
e) are usually oil cooled

Answer 37

c) may have brine pumped past the coils in an indirect system

Question 38

Which of the following is NOT an advantage of a factory assembled packaged refrigerant?

a) Components are designed to match each other.
b) Parts can be ordered and installed separately.
c) The unit is more compact.
d) Space requirements are minimized.
e) The unit is equipped with all the required auxiliary equipment.

Answer 38

b) Parts can be ordered and installed separately

Question 39

Which of the following statements about the economisers is false?

a) It controls the flow of liquid refrigerant from the low pressure evaporator to the high pressure condenser.
b) It is composed of two chambers.
c) The upper float chamber is connected to the bottom of the condenser.
d) The economiser float chamber is connected via the motor to the second stage inlet of the compressor. e) Liquid refrigerant levels in each chamber are controlled by a float operated valve in the evaporator.

Answer 39

a) It controls the flow of liquid refrigerant from the low pressure evaporator to the high pressure condenser

Question 40

Which of the following is a result of an economiser on the refrigeration system?

a) an intercooling effect on the compressor
b) reduction of the power required for compression in the second stage compressor
c) reduction of flash vapour in the evaporator
d) increase in the refrigerating capacity of a system
e) all of the above

Answer 40

e) all of the above

Question 41

In actual systems there will be a gradual pressure drop through each side of the system due to

a) the economiser
b) friction in the evaporator, condenser, and piping
c) decomposition of refrigerants
d) coefficients of expansion of system components
e) superheating effects

Answer 41

b) friction in the evaporator, condenser, and piping

Question 42

In a system controlled by a high pressure float valve insufficient liquid will cause which of the following results?

A) Starving the evaporator and reducing the capacity of the system

B) Boosting the compressor’s pressure

C) Automatic system shut down

D) The compressor will run continuously

E) Liquid being carried over to the compressor with the vapour

Answer 42

C) Automatic system shut down

Question 43

The safety head of a refrigeration compressor is designed to:

A) Relieve pressure due to liquid in the cylinder

B) Relieve high-pressure gas compression

C) Prevent explosion damage

D) Operate in place of a safety relief valve

E) Pop when the pressure is too high

Answer 43

E) Pop when the pressure is too high

Question 44

Pistons and connecting rods are found in which of the following types of compressors?

A)  Centrifugal
B)  Reciprocating
C)  Rotary & Centrifugal
D)  Reciprocating & Centrifugal
E)  Rotary

Answer 44

D) Reciprocating & Centrifugal

Question 45

Which of the following steps is not a step in the start-up of a reciprocating or rotary compressor
refrigerating system?

A) Valves in lines connecting suction gauges should be closed
B) Check the setting of high and low pressure cut out switches
C) All shutoff valves in the system should be open except bypass valves used for other purposes
D) Open shutoff valves in the cooling water supply and return lines of water-cooled condensers
E) Check oil level in the compressor, it should be at or above the centre of the sight glass

Answer 45

A) Valves in lines connecting suction gauges should be closed

Question 46

The absorber in the lithium bromide refrigeration system is equipped with a pump for which of the
following reasons?

A) To force water into a finely divided state
B) To decrease the refrigerant evaporation point
C) To keep the cycle pressure constant
D) To decrease contact between absorbent and refrigerant
E) To speed the absorption of water vapour

Answer 46

E) To speed the absorption of water vapour

Question 47

Which of the following statements about double tube condensers is true?

A) Cannot be used with air, cooled condensers
B) Has a small condenser for a large capacity system
C) Water flows in the inner tube in the opposite direction of the flow of refrigerant
D) Consists of two separate tubes side by side
E) Has the highest efficiency of the water-cooled condensers

Answer 47

C) Water flows in the inner tube in the opposite direction of the flow of refrigerant

Question 48

In order to lower the boiling point of the refrigerant in the lithium bromide system it is important that
the system maintain what?

A)  High absorbent circulation
B)  Very low temperatures
C)  High rate of refrigerant flow
D)  An extremely high vacuum
E)  Very high pressure

Answer 48

D) An extremely high vacuum

Question 49

When initially charging a refrigeration system:

A) It is done with a liquid refrigerant
B) It must be done at the compressor suction
C) Water should be added to dilute the refrigerant
D) It must be done with the liquid line shutoff valve open
E) It must be done after the unit is shut down

Answer 49

A) It is done with a liquid refrigerant

Question 50

The current code requires that pressure limiting devices shall be provided on all systems operating
above atmospheric pressure, containing more than _____ of group A1 refrigerant:

A)  10 kg
B)  5 kg
C)  7 kg
D)  9 kg
E)  3 kg

Answer 50

D) 9 kg

Question 51

Defective condenser operation is a result of the presence of all of the following except:

A)  Scale forming chemicals
B)  Dirty cooling water
C)  Loss of refrigerant
D)  Low coolant circulation
E)  Non-condensable gases

Answer 51

C) Loss of refrigerant

Question 52

Higher than normal head pressure is undesirable for all of the following reasons except:

A)  It increases power consumption
B)  It is detrimental to compressor lubrication
C)  It decreases condenser capacity
D)  It over stresses compressor parts
E)  It reduces compressor capacity

Answer 52

C) It decreases condenser capacity

Question 53

Over charging the system with refrigerant will create:

A) A high discharge condition
B) The formation of bubbles in the sight glass
C) A low oil pressure condition
D) The formation of frost at the compressor inlet
E) A low-pressure suction condition

Answer 53

A) A high discharge condition

Question 54

The type of operation that stops the compressor when the desired low temperature of the substance to
be cooled is reached and starts the compressor up again when the temperature rises to a set level is
called:

A)  Continuous operation with reduced output
B)  Intermittent operation
C)  Variable guide operation
D)  Unloading operation
E)  Cylinder bypass operation

Answer 54

B) Intermittent operation

Question 55

The net refrigerating effect of a refrigerant is the amount of heat:

A) Discharged by the condenser
B) Absorbed by the evaporator
C) Absorbed by the refrigerant in the evaporator
D) Discharged by the refrigerant in the evaporator
E) Absorbed by the refrigerant in the condenser

Answer 55

C) Absorbed by the refrigerant in the evaporator

Question 56

In the evaporator:

A) The refrigerant rejects heat to the cooling tower
B) The refrigerant is condensed
C) The refrigerant absorbs heat from the surrounding medium
D) The refrigerant absorbs heat from the compressor cooling system
E) The surrounding medium evaporates

Answer 56

C) The refrigerant absorbs heat from the surrounding medium