Refrigeration Flashcards
The condenser in a refrigeration system ____.
a. Desuperheat the vapor
b. Condenses the vapor from the compressor
c. Subcools the liquid refrigerant before it leaves the condenser
d. All of above
D
A normally operating water cooled condenser is operating with a 10 F differentail between water in and water out. If scale forms on the water tubes and the entering water is 85 F, which of the following is possible?
a. The outlet water temperature will be lower than expected
b. The system head pressure will rise
c. The water regulating valve will close
d. Both a and b are correct
D
In a water cooled condenser with dirty condenser tubes, the temperature difference between the refrigerant and the leaving water will be ____ when the tubes are clean.
a. Less than
b. Greater than
c. The same as
d. Slightly lower than
B
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
A
What can be used to maintain the head pressure of a system with a water cooled condeser?
a. Fan cycling
b. Dampers or louvers
c. Water regulating valve
d. All of the above
C
The typical design temperature for the water entering a recirculating water system condenser is 85 F, and most systems have a ______ rise across the condenser.
a. 1 F
b. 5 F
c. 10 F
d. 15 F
C
An air cooled condenser that is operating in a climate that has four distinct seasons must ______.
a. Have some type of head pressure control
b. Use a water regulating valve
c. Have a multi circuit evaporator
d. Operate with zero degrees of subcooling
A
T/F If the spring pressure of the water regulating valve is increased, the system head pressure will also increase.
T
T/F High head pressure from low ambient can cause insufficient refrigerant flow rates through metering devices, which in turn can starve evaporators.
F
T/F Low suction pressures, iced coils, short cycling, and inefficient cooling, can also result from low head pressures.
T
T/F Hard starting may also occur in a low ambient conditon, causing low head pressures.
T
The heat in the vicinity of the ________ gas has a tendency to cause any minerals in the water to deposit onto the tubes surface.
Discharge
An evaporative condenser uses air and _______ to desuperheat, condense, and subcool the refrigerant.
Water
If an air cooled condenser’s fan motor stops running, the head pressure will _____.
Rise
In order for a flooded condenser type head pressure control system to operate, a device called a ________ holds the extra refrigerant in warmer weather when the condenser doesn’t need to be flooded.
Receiver
The process of removing heat from aplace where it is not wanted and transferring that heat to a place where it makes little or no difference is known as
a. Cooling
b. Refrigeration
c. Defrosting
d. Temperature balancing
B
The household refrigerator fresh food compartment is a good example of ______ refrigeration.
a. Low temperature
b. Medium temperature
c. High temperature
d. Average temperature
B
The household refrigerator fresh food compartment typically ranges from
a. 25 F to 35 F
b. 28 F to 40 F
c. 30 F to 42 F
d. 32 F to 45 F
b
Low temperature food storage applications generally start at
a. -20 F
b. 0 F
c. 32 F
d. 40 F
B
High temperature refrigeration applications will normally provide box temperature of ______.
a. 20 to 40 F
b. 32 to 50 F
c. 47 to 60 F
d. 50 to 67 F
C
A refrigeration system designed for the storage of flowers or candy is considered a _____ type.
a. High temperature
b. Medium temperature
c. Low temperature
d. Sharp freezing
A
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
A
The boiling temperature and its relationship to the system exist in the ____.
a. Coil
b. Thermostat
c. Condenser
d. Evaporator
D
A typical evaporator operating temperature in an air conditioning system is _____.
a. 40 F
b. 55 F
c. 75 F
d. 200 F
A
The ______ of the liquid refrigerant determines the coil operating temperature.
a. Freezing point
b. Melting point
c. Transition temperature
d. Boiling temperature
D
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. 5 psig
b. 10 psig
c. 15 psig
d. 25 psig
D
Evaporators that operated full of liquid and are equipped with a device to keep the liquid refrigerant from passing to the compressor are known as ______.
a. Locked evaporator
b. Seized evaporators
c. Flooded evaporatos
d. Stoned evaporator
C
A direct expansion type evaporator is also called a _____.
a. Flooded evaporator
b. Dry type evaporator
c. Multi circuit evaporator
d. Stamped evaporator
B
______ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant.
a. Boiling temperature
b. Superheat
c. Dry heat
d. Vapor temperature
B
A typical superheat for an evaporator operating under normal conditions would be _____.
a. 4 to 6 F
b. 6 to 8 F
c. 8 to 12 F
d. 14 to 16 F
C
If the application requires a coil design to operate below freezing, there must be provision for ______.
a. Flooding the evaporator
b. Adding refrigerant
c. Defrost
d. Suction pressure control
C
If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 pisg, what is the pressure at the inlet of the evaporator?
a. 5 psig
b. 10 psig
c. 15 psig
d. 25 psig
D
T/F The refrigeration evaporator is a component that absorbs heat from the conditioned space into the refrigeration system.
T
T/F The film factor is a relationship between the medium giving up heat and the heat exchange surface.
T
T/F A stamped plate evaporator usually does not use a fan to move air across it.
T
T/F The capacity of the heat exchanger can vary with its height and depth.
F
T/F Every central split cooling system manufactured in the USA today must have a SEER of at least 10.
F
T/F TO check the performance of a dry type evaporator, the service technician would first make sure that the refrigerant coil is operating with enough liquid inside.
T
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
A
Most of the heat energy in the suction vapor entering the compressor is _____.
a. Subcooled from the condenser
b. Superheated from the condenser
c. superheated from the evaporator
d. subcooled from the evaporator
C
The temperature of the compressed gas leaving the compressor can best be described as _____.
a. Cold
b. Cool
c. Warm
d. Very warm
D
The screw compressor is used primarily in ______.
a. Large commercial and industrail systems
b. Residential
c. Small commercial refrigeration units
d. Domestic refrigeration
A
Rotay compressor are used primarily in _____.
a. Large industrial refrigeration and air conditioning systems
b. Residentail and light commercial air conditioning
c. Small commercial refrigeration units
d. High voltage redifential refrigeration
B
The clearance volume of a compressor cylinder is the
a. Amount of refrigerant vapor the compressor cylinder will hold during each strock
b. Volume by which the compressor is rated
c. Volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke
d. Total volume of the cylinder when the piston is at the bottom dead-center
C
The discus valve design is more efficient than a flapper valve design because ______.
a. It allows a compressor design with less clearance volume
b. It operates with less spring tension
c. The amount of expanded vapor in the cylinder is greater
d. It will not allow liquid refrigerant in the cylinder
A
Liquid entering the compression chamber of a reciprocating compressor can lead to ______.
a. Damaged vavles
b. Damaged piston rings
c. Damaged expansion valves
d. Both a and b
D
T/F Rotary compressors have pistons that rotate inside the cylinders.
F
T/F THe rotary screw compressor uses an open motor instead of the hermetic design.
T
T/F The sight glass on a semihermetic compressor is used to allow light to enter the crankcase to keep the oil warm.
F
T/F The shell of a hermetic type reciprocating compressor is generally condidered to be on the low pressure side of the system.
T
T/F The hermetic reciprocating compressor motor is essentially made of the same materials as an open type compressor motor.
F
T/F A bolted together motor-compressor assembly is sometimes referred to as a semihermetic type.
T
T/F Mufflers are used in many fully hermetic compressors to muffle compressors pulsation noise.
T
T/F The higher the rpm of a compressor, the higher the pumping efficiency.
F
T/F Scroll compressors are becoming popular because they can handle liquid floodback without compressor damage.
T
T/F The scroll compressor is one type of reciprocating compressor.
F
T/F SEER is calculated based on the total amount of cooling ( in BTU) the system will provide over the entire season, divided by the total number Watt-Hours it will consume.
T
T/F Because a scroll compressor’s has fewer moving parts, it operates much quiter than other compressor designs and technologies.
T
Excessive heat and pressure on the oil in a compressor can cause oil to break down and cause the formation of ________ and acid.
Carbon
The compression ratio for an R-22 compressor operating with 68.5 psig suction pressure and 260 psig heat pressure is ________.
3.34
The type of compressor that is driven by a belt is the ______ compressor.
Open
A compressor that has the motor and compressor in one housing that is welded together is called a ______ type.
Hermetic
A compressor that has the motor and compressor in a housing that is bolted together is called a ________ type.
semihermetic
Pistons are connected to the crankcase using connecting rods and ______.
Wrist pins
When the pistons reaches the bottom of its stroke, it is called _________.
Bottom dead center
The space at the top of the cylinder when the piston reaches the top of its strock is called
Clearance volume
______ is a bimetallic disc that senses compressor discharge temperature and opens at 270 F.
TOD
__________ opens at approximately 400 + – 50 psig differential between high and low side pressure for R-22 and at a 500 to 625 psi differential for R-410a.
Internal pressure relief
The following is a function of an explosion device.
a. Produce a reduction in the pressure on the liquid refrigerant
b. Regulate the flow of refrigerant into the evaporator
c. Lower the boiling point of the refrigerant far enough below the temperature of the load to get the needed heat transfer rate
d. All of the above
D
A thermostatic expansion valve meters refrigerant flow to the evaporator based on the ______.
a. Rate of liquid vaporization
b. Evaporator suction line superheat
c. External equalizer pressure
d. All of the above
B
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. The bulb pressure would increase and the thermostatic expansion valve would open
b. The superheat in the evaporator would decrease
c. The evaporating pressure and the compressor’s suction pressure would increase
d. All of the above are correct
D
The TXV sensing bulb is mounted
a. On the liquid line between the condenser and the TXV
b. At the inlet to the condenser
c. On the suction line between the evaporator and the compressor
d. On the compressor discharge line
C
The cross liquid charge bulb at the TXV contains fluid that _______.
a. Has similar characteristics to the system fluid to prevent liquid refrigerant from entering
b. Has different characteristics from the system fluid
c. cause the vavle to stay open during the off cycle
d. Follows the system’s pressure-temperature relationship
B
When the load on the evaportaor 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
A
If the thermal bulb assembly develops a leak, what will occur?
a. All of the system’s refrigerant will leak out
b. The bulb pressure will reduce and the valve will close
c. The vavle will open to allow more refrigerant to flow
d. It will have no effect on system operation
B
The purpose of an external equalizer in a TXV is to _____.
a. Compensate for excessive evaporator pressure drop
b. Allow system to equilize faster
c. Prevent the expansion valve from frosting up
d. Allow refrigerant to expand in the compressor
A
Balanced port TXVs are used to ______ ambient temperature.
a. Feed refrigerant at a normal rate with low
b. Feed refrigerant at a normal rate with high
c. Stop refrigerant flow with high
d. Stop refrigerant flow with low
A
The pressure limiting TXV
a. Allows the compressor to operate at low condenser entering air temperature
b. Shuts off the condenser fan during hot pull down
c. Maintians the full refrigerant flow rate during a hot pullldown
d. Keeps the suction pressure to the compressor down during a hot pulldown
D
The purpose of a capillary tube is to
a. Regulate the refrigerant flow into the evaporator
b. Lower the pressure of the liquid refrigerant
c. Lower the boiling point of the refrigerant
d. All of the above
D
T/F Pressure entering the compressor that is tooo high will cause the density of suction gases entering the compressor to increase.
T
T/F The pressure limiting TXV is desirable in low temperature applications because it keeps the suction pressure to the compressor down during hot pulldown.
T
T/F The soild state controlled step motor valve has temperature sensor, or thermistor, as one of its inputs.
T
