RACT Unit 21 Review questions/Practice test

Question 1

What is the function of the evaporator in the refrigeration system?

A) to add heat to the space or product being coole

B) to add humidity to the space being refrigerated

C) It condenses superheated refrigerant vapour to a liquid

D) absorbs heat into the refrigeration system

Answer 1

D) absorbs heat

Question 2

Refrigerant in the evaporator;

A) changes from vapour to liquid

B) changes from liquid to vapour

C) stays in vapour state

Answer 2

B) changes from liquid to vapour

Question 3

The sensible heat that is added to a saturated vapour after all of the liquid has boiled away is referred to as;

A) superheat

B) Latent heat

C) Sub-cooling

D) Specific heat

Answer 3

superheat

Question 4

What determines the pressure on the low pressure side of the system?

A) the condensing temp of the refrigerant in the condenser

B) the length of the liquid line feeding the TXV

C) The boiling temperature of the refrigerant in the evap

Answer 4

the boiling point of the refrigerant in the evaporator

Question 5

A refrigeration systems evaporator typically runs at about ________ of super heat

Answer 5

8 to 12F

Question 6

What does a high evaporator
superheat indicate?

A) flooded evap

B) starved evap

C) proper system operation

Answer 6

starved evaporator

Question 7

A low evaporator superheat may indicate;

A) undercharge
B) system restriction
C) overcharge
D) high heat load

Answer 7

overcharge

Question 8

Why is a multi circuit evaporator used?

A) to reduce pressure drop through larger evaporators

B) To ensure proper compressor operation

C) to prevent ice build on the fine

D) easily defrosted in low temp applications

Answer 8

to reduce pressure drop

Question 9

Flooded evaporators typically use a __________ type of expansion device

a) automatic
b) float
c) TXV
d) fixed bore

Answer 9

float

Question 10

An evaporator that does not operate flooded is thought of as what type of evaporator?

A) A dry type

B) a starved type

C) a float type

D) a low pressure type

Answer 10

A dry type

Question 11

When an evaporator experiences a heat load increase, the suction pressure

a) remains constant
b) decreases
c) varies up and down
d) increases

Answer 11

increases

Question 12

What is commonly used to defrost the ice from a low temp evaporator?

A) random or off-cycle defrost
B) hot gas or electric resistance heat defrost
C) Off-cycle or manual defrost
D) Low temperature evaporators do not require a defrost

Answer 12

hot gas or electrical heaters

Question 13

A medium temperature refrigeration box typically operates within what temperature range?

A) 28 to 40
B) 40 to 60
C) 0 to 220
D) 0 to 50

Answer 13

28 to 40F

Question 14

The greater the difference in temperature between the evaporator and the air being cooled;

A) the less moisture will be removed from the air
B) The less moisture will be added to the air
C) The more moisture will be added to the air
D) The more moisture will be removed from the air

Answer 14

The more moisture will be removed

Question 15

A finned tube evaporator equipped with fans is called a _______ evaporator

A) bare tube
B) stamped
C) induced or forced draft
D) liquid cooling

Answer 15

bare pipe

Question 16

Which of the following is not a function of an evaporator efficiency control?

A) minors evap efficiency and
performance
B) Initiates a defrost when coil efficiency drops below 90%
C) Contains an ethernet network device that supports industry standard protocols
D) regulates condensate removal by activating condensate pump

Answer 16

C)

Question 17

A medium temperature evaporator uses a _________ defrost method

A) hot gas
B) random or off cycle
C) electric resistance heat
D) liquid injection

Answer 17

B) random or off-cycle

Question 18

The difference in the amount of heat (in btu/lb) that the refrigerant contains at the point where it enters the evaporator and the point at which it leaves the evaporator is known as

A) mass flow rate
B) total heat of rejection
C) the net refrigeration effect
D) The heat of compression

Answer 18

The net refrigeration effect

Question 19

Low temperature refrigeration systems typically operate at what temperature range?

Answer 19

0 to -20F

Question 20

high temp refrigeration systems typically operate at?

Answer 20

47 to 60F

Question 21

The difference in temperature between the boiling refrigerant temperature and the evaporator is known as ____________

a) evaporator superheat
b) delta T
c) suction line superheat
d) temperature difference

Answer 21

a) evaporator superheat

Question 22

Low temperature food storage applications typically have a temperature range of __________

a) 0 to -32F
b) 0 to -20F
c) -20F to -32F
d) 0 to 32F

Answer 22

b) 0 to -20F

Question 23

When the evaporator removes heat from the air and lowers the temperature of the air, ___________

a) sensible heat is removed from the air
b) moisture is added to the air
c) refrigerant vapour condenses to a liquid
d) latent heat is added to the air

Answer 23

a) sensible heat is removed from the air

Question 24

When moisture is removed from the air, latent heat is removed

True or False

Answer 24

True

Question 25

Natural-convection evaporators use a blower to force or induce air over the coil to improve the efficiency of the heat exchange

Answer 25

false

Question 26

When a refrigerated space has been allowed to warm up considerably, the system must ___________

a) be overcharged to remove the excess heat
b) be defrosted at regular intervals
c) go through a hot pull down
d) turned off and the product being cooled moved to another cooler

Answer 26

c) go through a hot pull down

Question 27

Flooding the compressor crankcase with liquid refrigerant can cause _________

a) oil foaming
b) excessive superheat
c) starved evaporator
d) moisture to accumulate in the compressor oil

Answer 27

a) oil foaming

Question 28

Low-temperature evaporator coils ___________

a) operate the same as medium temperature evaporator coils
b) have fewer fins per inch than medium temperature evaporator coils
c) require more oil circulation that medium temperature evaporator coils
d) have more fins per inch than medium temperature evaporator coils

Answer 28

b) have fewer fins per inch than medium temp evaporator coils

Question 29

Two common methods for defrosting a low temperature evaporator are _____________

a) off-cycle and got gas
b) reverse cycle and hot gas
c) off-cycle and electric heat
d) hot gas and electric heat

Answer 29

d) hot gas and electric heat

Question 30

When liquid refrigerant floods the compressor crankcase, the oil level in the crankcase can drop causing ________

a) condenser flooding
b) excessive superheat
c) bearing washout
d) valve damage

Answer 30

c) bearing washout