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Worksheets104 final
Total questions: 75
Worksheet time: 1hrs 15mins
Name
Class
Date
1.
The process of removing heat from a place where it is not wanted and transferring that heat to a place where it makes little or no difference is known as ____.
a)
refrigeration
b)
cooling
c)
defrosting
d)
temperature balancing
2.
The household refrigerator fresh-food compartment typically ranges from ____.
a)
28 to 40°F
b)
25 to 35°F
c)
30 to 42°F
d)
32 to 45°F
3.
Low-temperature food storage applications generally start at ____.
a)
0°F
b)
-20°F
c)
32°F
d)
40°F
4.
High-temperature refrigeration applications will normally provide box temperatures of ____.
a)
47 to 60°F
b)
32 to 50°F
c)
20 to 40°F
d)
50 to 67°F
5.
The ____ in a refrigeration system is responsible for absorbing heat into the system from whatever medium is to be cooled.
a)
evaporator
b)
thermostat
c)
compressor
d)
condenser
6.
The boiling temperature and its relationship to the system exist in the ____.
a)
evaporator
b)
coil
c)
compressor
d)
condenser
7.
The ____ of the liquid refrigerant determines the coil operating temperature.
a)
boiling temperature
b)
freezing point
c)
melting point
d)
transition temperature
8.
If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?
a)
25 psig
b)
5 psig
c)
10 psig
d)
15 psig
9.
Evaporators that are operated full of liquid and are equipped with a device to keep the liquid refrigerant from passing to the compressor are known as ____.
a)
flooded evaporators
b)
locked evaporators
c)
seized evaporators
d)
stoned evaporators
10.
A direct expansion-type evaporator is also called a ____.
a)
dry-type evaporator
b)
flooded evaporator
c)
multi-circuit evaporator
d)
stamped evaporator
11.
____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant.
a)
Superheat
b)
Dryheat
c)
Boiling temperature
d)
Vapor temperature
12.
A typical superheat for an evaporator operating under normal conditions would be ____.
a)
8 to 12°F
b)
4 to 6°F
c)
6 to 8°F
d)
14 to 16°F
13.
If the application requires a coil design to operate below freezing, there must be provision for ____.
a)
defrost
b)
flooding the evaporator
c)
adding refrigerant
d)
suction pressure control
14.
A stamped plate evaporator usually does not use a fan to move air across it.
a)
True
b)
False
15.
____________________-temperature refrigeration produces temperatures below the freezing point of water.
a)
Low
b)
High
c)
Medium
d)
Neutral
16.
As a rule of thumb, the temperature of the evaporator should be about ____________________°F colder than the box temperature.
a)
15
b)
16
c)
20
d)
14
17.
When the refrigerant vapor is saturated with heat it is known as a(n) ____________________.
a)
Saturated vapor
b)
Saturated liquid
c)
Boiling point
d)
Humidified vapor
18.
____________________ evaporators are used when the coil would become too long for a single circuit, percent vapor.
a)
Multi-circuit
b)
Single-circuit
c)
Double-circuit
d)
Variable-circuit
19.
A defrost system that pipes the compressor discharge vapor directly to the evaporator is called a(n)
a)
Hot gas defrost
b)
Defrost
c)
Accumulated Moisture defrost
d)
Heat defrost
20.
Define superheat.
a)
Superheat is the sensible heat added to the vapor refrigerant after the change of state has occurred.
b)
Superheat is the latent heat added to the vapor refrigerant after the change of state has occurred.
c)
Superheat is the sensible heat added to the liquid refrigerant after the change of state has occurred.
d)
Superheat is the sensible heat subtracted to the vapor refrigerant after the change of state has occurred.
21.
What is a starved coil?
a)
When a metering device is not feeding enough refrigerant to the coil, the coil is said to be a starved coil..
b)
When a compressor is not feeding enough refrigerant to the coil, the coil is said to be a starved coil..
c)
When a metering device is feeding refrigerant to the coil, the coil is said to be a starved coil..
d)
When a metering device is feeding too much refrigerant to the coil, the coil is said to be a starved coil..
22.
What is a typical problem on the liquid side of a liquid cooling evaporator?
a)
Mineral deposits that may build up on the liquid side and cause a poor heat exchange.
b)
Metal deposits that may build up on the liquid side and cause a poor heat exchange.
c)
Mineral deposits that may build up on the liquid side and cause a good heat exchange.
d)
Metal deposits that may build up on the liquid side and cause a good heat exchange.
23.
Why are the fins of a low temperature evaporator spaced wider apart than those on a high temperature evaporator?
a)
This allows for the formation of frost without blocking air flow.
b)
This allows for the formation of frost blocking air flow.
c)
This doesn't allow for the formation of frost without blocking air flow.
d)
This allows for the formation of heat without blocking air flow.
24.
The refrigerant in a condenser in a refrigeration system ____.
a)
rejects heat
b)
absorbs heat
c)
changes to a vapor
d)
is under lower pressure than the evaporator
25.
Mineral deposits on the water side of a water-cooled condenser act as a(n) ____.
a)
insulator
b)
conductor of heat
c)
cleaning solution
d)
They have no effect on the operation of the condenser.
26.
The water circuit in shell-and-coil and tube-within-a-tube coil condensers must be cleaned ____.
a)
chemically
b)
by removing the end caps
c)
with a brush
d)
by air pressure
27.
The shell-and-tube condenser is cleaned ____.
a)
with a brush after removing the end caps
b)
only with chemicals
c)
with compressed air
d)
with a vacuum cleaner
28.
In a water-cooled condenser, a regulating valve is used to control the ____.
a)
refrigerant head pressure
b)
refrigerant flow through the pressure reducing device
c)
suction pressure
d)
water temperature
29.
A water regulating valve helps to maintain a system's head pressure by modulating the flow of refrigerant through the condenser.
a)
False
b)
True
30.
When the evaporative condenser is used in cold climates, freeze protection must be provided in winter.
a)
True
b)
False
31.
If the spring pressure of a water regulating valve is increased, the system head pressure will also increase.
a)
True
b)
False
32.
Low suction pressures, iced coils, short cycling, and inefficient cooling, can also result from low head pressures.
a)
True
b)
False
33.
In a recirculating water system condenser, the leaving water temperature is normally ____________________°F lower than the condensing temperature of the refrigerant.
a)
10
b)
12
c)
8
d)
9
34.
An evaporative condenser uses air and ____________________ to desuperheat, condense, and subcool the refrigerant.
a)
Water
b)
Oil
c)
Nitrogen
d)
None of the above
35.
If an air-cooled condenser's fan motor stops running, the head pressure will ___________________.
a)
Increase
b)
Decrease
c)
Stay the same
d)
None of the above
36.
In order for a flooded condenser type head pressure control system to operate, a device called a(n) ____________________ holds the extra refrigerant in warmer weather when the condenser doesn’t need to be flooded.
a)
Receiver
b)
Accumulator
c)
Evaporator
d)
Compressor
37.
What is the condenser saturation temperature if there is 20°F of subcooling and the outlet temperature of the refrigerant is 90°F?
a)
110°F
b)
70°F
c)
180°F
d)
45.5°F
38.
Define "subcooling."
a)
Subcooling is the reduction of the temperature of a liquid below its condensing temperature.
b)
Subcooling is the increase of the temperature of a liquid below its condensing temperature.
c)
Subcooling is the reduction of the temperature of a vapor below its condensing temperature.
d)
Subcooling is the increase of the temperature of a vapor below its condensing temperature.
39.
If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____.
a)
will increase
b)
will decrease
c)
will remain the same
d)
cannot be determined
40.
Most of the heat energy in the suction vapor entering the compressor is ____.
a)
superheated from the evaporator
b)
subcooled from the condenser
c)
superheated from the condenser
d)
subcooled from the evaporator
41.
The screw compressor is used primarily in ____.
a)
large commercial and industrial systems
b)
residential air conditioning
c)
small commercial refrigeration units
d)
domestic refrigerators
42.
Rotary compressors are used primarily in ____.
a)
residential and light commercial air-conditioning
b)
large industrial refrigeration and air conditioning systems
c)
small commercial refrigeration units
d)
high volume residential refrigeration
43.
The clearance volume of a compressor cylinder is the ____.
a)
volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke
b)
amount of refrigerant vapor the compressor cylinder will hold during each stroke
c)
volume by which the compressor is rated
d)
total volume of the cylinder when the piston is at the bottom dead-center
44.
Mufflers are used in many fully hermetic compressors to muffle compressor pulsation noise.
a)
True
b)
False
45.
Scroll compressors are becoming popular because they can handle liquid floodback without compressor damage.
a)
True
b)
False
46.
The higher the rpm of a compressor, the higher the pumping efficiency.
a)
False
b)
True
47.
Excessive heat and pressure on the oil in a compressor can cause oil to break down and cause the formation of ____________________ and acid.
a)
Carbon
b)
Oxygen
c)
Carbon dioxide
d)
Nitrogen
48.
The compression ratio for an R-22 compressor operating with 68.5 psig suction pressure and 260 psig heat pressure is ____________________.
a)
3.3
b)
3.5
c)
5.3
d)
5.5
49.
The type of compressor that is driven by a belt is the ____________________ compressor.
a)
Open drive
b)
Closed drive
c)
Reverse drive
d)
Neutral drive
50.
A compressor that has the motor and compressor in one housing that is welded together is called a(n) ____________________ type.
a)
Hermetic
b)
Open
c)
Drive
d)
Semi-hermetic
51.
A compressor that has the motor and compressor in a housing that is bolted together is called a(n) ____________________ type.
a)
Semi-Hermetic
b)
Open
c)
Drive
d)
Hermetic
52.
When the piston reaches the bottom of its stroke, it is called ____________________.
a)
Bottom dead-center
b)
Open dead-center
c)
Bottom dead-middle
d)
Closed dead-center
53.
The space at the top of the cylinder when the piston reaches the top of its stroke is called ____________________.
a)
clearance volume
b)
clearance distance
c)
clearance meter
d)
clearance center
54.
____________________ is a bimetallic disc that senses compressor discharge temperature and opens at 270ºF.
a)
TOD (Temperature operated disk)
b)
POD (Pressure operated disk)
c)
EOD (Electrically operated disk)
d)
TOD (Technical operated disk)
55.
____________________ opens at approximately 400 ± 50 psi differential between high- and low-side pressures for R-22, and at a 500 to 625 psi differential for R-410A.
a)
IPR (Internal pressure relief)
b)
OPR (Open pressure relief)
c)
CPR (Closed pressure relief)
d)
EPR (External pressure relief)
56.
A decrease in suction pressure will have what effect on a reciprocating compressor?
a)
The compressor will pump less refrigerant.
b)
The condenser will pump less refrigerant.
c)
The evaporator will pump less refrigerant.
d)
The compressor will pump more refrigerant.
57.
The following is a function of an expansion device: ____.
a)
All of the above.
b)
produce a reduction in the pressure on the liquid refrigerant
c)
regulate the flow of refrigerant into the evaporator
d)
lower the boiling point of the refrigerant far enough below the temperature of the load to get the needed heat transfer rate
58.
A thermostatic expansion valve meters refrigerant flow to the evaporator based on the ____.
a)
evaporator suction line superheat
b)
rate of liquid vaporization
c)
external equalizer pressure
d)
All of the above.
59.
If a thermostatic expansion valve's thermal bulb came loose from the suction line at the outlet of the evaporator, which of the following could result?
a)
All of the above are correct.
b)
The bulb pressure would increase and the thermostatic expansion valve would open.
c)
The superheat in the evaporator would decrease.
d)
The evaporating pressure and the compressor’s suction pressure would increase.
60.
The TXV sensing bulb is mounted ____.
a)
on the suction line between the evaporator and the compressor
b)
on the liquid line between the condenser and the TXV
c)
at the inlet to the condenser
d)
on the compressor discharge line
61.
The cross liquid charge bulb at the TXV contains fluid that ____.
a)
has different characteristics from the system fluid
b)
has similar characteristics to the system fluid to prevent liquid refrigerant from entering the suction line
c)
causes the valve to stay open during the off cycle
d)
follows the system’s pressure-temperature relationship
62.
When the load on the evaporator increases, the TXV ____.
a)
increases the flow of refrigerant
b)
decreases the flow of refrigerant
c)
maintains constant head pressure
d)
decreases the pressure drop across the evaporator
63.
The purpose of an external equalizer in a TXV is to ____.
a)
compensate for excessive evaporator pressure drop
b)
allow system to equalize faster
c)
prevent the expansion valve from frosting up
d)
allow refrigerant to expand in the compressor
64.
The pressure-limiting TXV ____.
a)
keeps the suction pressure to the compressor down during a hot pulldown
b)
allows the compressor to operate at low condenser entering air temperatures
c)
maintains the full refrigerant flow rate during a hot pulldown
d)
stop refrigerant flow with low
65.
The pressure-limiting TXV is desirable in low temperature applications because it keeps the suction pressure to the compressor down during hot pulldowns.
a)
True
b)
False
66.
An automatic expansion valve uses a thermal bulb to help control the amount of refrigerant being fed into the evaporator.
a)
False
b)
True
67.
When the evaporator pressure drops, the automatic expansion valve will open to allow more refrigerant to enter the evaporator.
a)
True
b)
False
68.
AXVs are usually found on smaller equipment with somewhat constant evaporator loads.
a)
True
b)
False
69.
A capillary tube metering device controls the refrigerant flow by pressure drop.
a)
True
b)
False
70.
The TXV maintains a constant ____________________ in the evaporator.
a)
Superheat
b)
Subcool
c)
Flow
d)
Control
71.
As the evaporator load increases, an automatic expansion valve will ____________________ to maintain the suction pressure at the set point.
a)
Close
b)
Open
c)
Flow
d)
Control
72.
The two pressures that push to close a thermostatic expansion valve are the ____________________ pressure and the evaporator pressure.
a)
Spring
b)
Electrical
c)
Temperature
d)
Control
73.
The automatic expansion valve maintains a constant ____________________ in the evaporator.
a)
Pressure
b)
Electrical
c)
Temperature
d)
Control
74.
When is an external equalizer-type TXV required?
a)
This is required when the evaporator has an excessive pressure drop.
b)
This is required when the evaporator has a normal pressure drop.
c)
This is required when the evaporator has a pressure drop.
d)
This is required when the evaporator has a minimal pressure drop.
75.
What two pressures control the operation of an automatic expansion valve?
a)
They are the spring pressure and evaporator pressure.
b)
They are the electrical pressure and evaporator pressure.
c)
They are the temperature pressure and evaporator pressure.
d)
They are the control pressure and evaporator pressure.
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