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
T/F The step-motor valve uses a small motor to control the valve’s port, which in turn controls evaporator superheat.
T
T/F The pin or valve port piston of the electronic step- motor enxpansion valve cna move in a linear motion of 0.0000783 in./step.
T
T/F An automatic expansion valve uses a thermal bulb to help control the amount of refrigerant being fed into the evaporator.
F
T/F When the evaporator pressure drops, the automatic expansion valve will open to allow more refirgerant to enter the evaporator.
T
T/F AXVs are usually found on smaller equipment with somewhat constant evaporator load.
T
T/F A capillary tube metering device controls the refrigerant flow by pressure drop.
T
The TXV maintains a constant ___________ in the evaporator.
Superheat
As the evaporator load increases, an automatic expansion valve will ________ to maintain the suction pressure at the set point.
Close
The two pressures that push to close a thermostatic expansion valve are the _____ pressure and the evaporator pressure.
Spring
The automatic expansion valve maintains a constant _________ in the evaporator.
Pressure
Two temperature operation of a refrigeration system is necessary when _____.
a. The compressor must be protected from overloading
b. More than one evaporator is used with a compressor
c. The coil in the evaporator is excessively long
d. A multiple circuit distributer is used
B
The EPR valve is installed in the suction line at the evaporator outlet and it _____.
a. Modulates the refrigerant vapor to the compressor
b. Prevents the boiling point in the evaporator from dropping below a pre set point
c. When used with a TXV the system has the characteristics of maintaining a constant superheat and keeping the pressure form going too low
d. All of the above
D
EPR valves are also referred to as ______ valves.
a. DRP
b. ORC
c. ORN
d. ORI
D
Technician A says that a multi evaporator system equipped with three evaporators (one high temperature, one medium temperature and one low temperature) will use one evaporator pressure regulator and two flow check valves. Technician B says that the crankcase pressure regulator is used to kepp the low temperature compessor from overloading on a hot pulldone. Which of the following statements is correct?
a. Technician A is correct. Technicain B is correct
b. Technician A is correct. Technican B is incorrect
c. Technician A is incorrect. Technicain B is correct
d. Technician A is incorrect. Technican B is incorrect
C
To protect the compressor during periods of hot pulldown a ______ valve is used.
a. TXV
b. EPR
c. CPR
d. LAC
C
The refrigerant compressor motor can be operated at about ______ % over its rated capacity without harm during the pulldown.
a. 5
b. 10
c. 15
d. 20
B
Refrigeration systems are designed to operate year round. For this reason they are equipped with ______.
a. Relief valves
b. A low ambient control
c. Oversized evaporator coils
d. EEPR vavles
B
Which of the following is a type of low ambient temperature head pressure control?
a. CPR
b. EPR
c. Fan cycling
d. Off cycle defrost
C
Which of the following is another type of low ambient temperature head pressure control?
a. Air volume control using shutters and fan cycling
b. Programmed defrost timer
c. Timer and liquid line solenoid for automatic pump down
d. Compressor internal heat
A
Frequently on smaller condensing units, one fan will run continuously and the other fan will be cycled on and off with a _______.
a. Ambient temperatue
b. Ambient pressure valve
c. Thermal expansion valve
d. Thermal control valve
A
________ are snap acting valves that open and close very fast when the electrical energy is applied to the coil.
a. Contactors
b. Condenser
c. Relays
d. Solenoid valves
D
When a system pumps down, where is the refrigerant stored?
a. Condensr and reciever
b. Evaporator and compressor
c. Condenser and compressor
d. Both a and c
A
Random defrost is accomplished ____.
a. With a timer
b. Using a high pressure control
c. Using a low pressure control
d. When the refrigerant system has enough reserve capacity to cool more than the load requirement
D
Defrost using internal heat is accomplished using _______.
a. A sail switch
b. Electric heating elements
c. Hot gas from the compressor
d. Mullion heaters
C
How does the receiver ensure that only 100% liquid refrigerant enters the liquid line?
a. By means of a dip tube
b. It only allows refrigerant to enter the liquid line when it is filled with liquid
c. The spring loaded relief valve opens
d. None of the above are correct
A
The normal position for a suction service valve during normal operation is ____.
a. Back seated
b. Front seated
c. Midseated
d. Any of the three
A
T/F Two temperature operation is desirable when more than one evaporator is used with a compressor
T
T/F The crankcase pressure regulator (CPR) puts a limit on the pressure that can return to the compressor
T
T/F A suction line accumlator is used to ensure that liquid refrigerant enters the compressor.
F
T/F Oil separators work on the principle of low refrigerant and oil velocity.
T
T/F Helical oil separators are about 58% efficient in separating oil.
F
Automatic pumpdown systems are equipped with a _______ to prevent refrigerant from reaching the evaporator.
Solenoid valve
The _______ is a mechanical control that keeps the refrigerant pressure in the evaporator from going below a predetermined point.
EPR
Two types of relief valves are the spring loaded valve and the ______ valve.
One time
The spring loaded type of relief valve is normally brass with a _______ seat.
Neopreme
The one time relief valve is caused to relieve by ______.
Temperature
To protect a refrigeration compressor when refrigerant loss occurs, a ______ control is used.
Low pressure
In a kitchen \_\_\_\_ condensing units may be easier to maintain. A. Self contained B. Remote C. Local D. Hybrid
B
The tree way heat reclaim valves in most heat reclaim systems are \_\_\_ operated. A. Relay B. Contact C. Switch D. Solenoid
D
The heat reclaim valve is a three way valve that is activated by a solenoid operated by a \_\_\_. A. Pilot B. Reload C. Preload D. Pressure
A
When a parallel heat reclaim system is used, the heat reclaim condenser must be sized to handle \_\_\_\_\_\_% of the refrigeration system’s rejected heat when in the heat reclaim mode. A. 50 B. 80 C. 70 D.100
D
Heaters that are made with resistance type wire run just under the surface of a the cabinet are called A. Anticipation B. Relief C. Mullion D. Reclamation
C
Knock down walk in cooler are constructed of interlocking panels from \_\_\_\_\_ thick. A. 1 in to 4 in B. 1in to 6 in C. 2 in to 4 in D. 2 in to 6 in
A
In condensate removal, the drain lines should be sloped downward about \_\_\_\_ in per foot for proper drainage. A. 1/8 B. 1/6 C. 1/4 D. 1/2
C
The precharge tubing used for installing refrigeration piping is called a A. Line set B. Gauge set C. Log set D. Completion set
A
One of the advantages of parrallel compressor system is A. Load matching B. Flexibility C. Less compressor cycling D. All of the above
F
The most popular secondary fluid currently used in refrigeration systems is A. HFE B. Ethylene glycol C. HCFC D. Propylene glycol
D
One of the disadvantages of the secondary fluid refrigeration system is A. Greater leak potential B. More critical piping C. Longer defrost periods D. Higher cost of the equipment
D
At its triple point, CO2 can exist as A. Vapor B. Liquid C. Solid D. All of the above
D
Refrigeration compressed air driers typically run \_\_\_\_ % of the time. A. 30 B. 50 C. 80 D. 100
D
The primary advantage of parallel compressor systems is their
A. Higher efficiency
B. Nearly exact lid matching ability
C. Smaller locked rotor amperage
D. Limited effect of a compressor malfunction
B
The air used for pneumatic controls must be A. Hot B. Dry C. Moist D. Rectified
B
T/F when purchase cost alone is considered in selecting refrigeration equipment, the equipment may not perform acceptably
T
T/F An open case is more efficient than a closed case
F
T/F Self contained equipment normally plugs into a 120v or 230 v electrical outlet.
T
T/F Often parallel compressor systems employ a satellite or booster compressor
T
T/F Carbon dioxide is one of the newest refrigerants
F
T/F CO2 ammonia propane butane and isobutane are all natural refrigerants
T
T/F Distributed supermarket refrigeration modules that are located very close to the display cases they refrigerate are becoming increasingly popular
T
T/F Refrigerated air driers are normally self contained refrigeration systems that may be air cooled or water cooled
T
Retail stores use _____ refrigeration units for merchandising their products
Open display
All refrigeration equipment must have some means for disposing of the _______ that is gathered on the evaporator
Condensation
When the inlet of the evaporator cabinet is below freezing, heat has to be provided to keep the condensate in the line _____.
From freezing
The precharged tubing for refrigeration piping is _____ at both ends and has quick connect fittings
Sealed
______ are basically refrigeration systems located in the air supply, after the storage tank.
Air driers
Tremendous forces that can cause refrigeration lines and valves to rupture
Liquid hammer
Removes refrigerant from the heat reclaim coil when it is not being used
Bleed ports
Usually installed in the heat reclaim pump out or bleed line to prevent migration of refrigerant to the coldest location
Check valve
When air is used for controls
Pneumatic control
Applies a false load on the evaporator when there is no load
Hot gas bypass valve
Package ice machines store their own ice at ______ F in a bin below the ice maker.
a. 10
b. 18
c. 24
d. 32
D
Most package ice makers are ____ cooled
a. water
b. air
c. moisture
d. refrigerant
b
______ ice is normally made in a vertical refrigerated cylinder surrounded by the evaporator on the outside.
a. Soild
b. Cube
c. Flake
d. Chip
c
The auger in a flake ice maker has cutting surfaces called ______.
a. flights
b. fins
c. shafts
d. gears
A
A ______ is used to turn the auger in a flake ice machine.
a. Step motor
b. Geared motor
c. Worm motor
d. Hydraulic motor
B
Most ice flackers have a ______ that reduces the auger drive motor’s speed from about 1725 rpm to 9 to 16rpm.
a. gear improvement drive
b. gear intensive drive
c. gear shift drive
d. gear reduction drive
d
_______ evaporators have ice cups designed to cause the ice to fall out of the cups during defrost.
a. Vertical
b. Horizontal
c. Hybrid
d. Linear
A
______ ice cube machines usually have vertical evaporator plates with water flowing over the individual cells.
a. Modular
b. Linear
c. Cell type
d. Cup type
C
_____ between the evaporator cells allow air entering from the edges of the ice to travel along the entire ice slab and relieve the suction force.
a. Space holes
b. Weep holes
c. Release spots
d. Weep space
b
______ are simply small computers that contain stored programs or algoriths.
a. Auto processors
b. Signal processors
c. Microcontrollers
d. Microprocessors
D
For maximum efficiency, individual ice machine models have different programs called algorithms stored in their _____.
a. EEPROM
b. ERAM
c. EPRAM
d. PRAM
a
Microprocessors are often referred to as _____.
a. signal controllers
b. digital controllers
c. integrated device controllers
d. integrated circuit controllers
d
Many filter manugacturers use ______ to inhibit calcium or lime scale buildup.
a. Wool
b. Polysorbate
c. Polyshosphate
d. Polyphenols
C
Most package ice machines are designed to be located in ambient temperature of ______.
a. 30 F to 110 F
b. 40 F to 115 F
c. 50 F to 115 F
d. 50 F to 120 F
b
T/F When using cleaning and snaitizing chemicals, it is unnecessary to wear protective clothing and eyewear.
F
T/F Ice making machines are the same as ice holding machines such as those seen on the outside of a convenience store or service station.
F
T/F The gear motor assembly is less prone to failure than any other part in the ice flaker.
F
T/F Manufacturers of ice flakers install thermal overload controls in the motor windings or a manual reset current type overload control.
T
T/F It is important that the auger does not wobble within the freezing cylinder or evaporator.
T
T/F Water levels can be sensed and controlled by a probe located in the water reservoir.
T
T/F Soild forms of ice last longer because there is more weight with less surface area.
T
T/F Most ice makers use a hot gas harvest or defrost to melt an ice sheet off the evaporator.
T
T/F Ice is not considered a food source.
F
It is recommended that at least _______ a year, the probe should be removed from the water reservoir and cleaned.
Twice a year
The ______ is usually made of two reed switches and two floats.
Dual float
________ type devices are usually located in the spout.
Mechanical flappers
_______ sense the buildup of ice by infrared technology. This control allows the ice machine to shut down before the ice chokes the spout opening.
Infrared Eye
______ controls use sound waves and vibrations, which are reflected back to the control from the ice.
Sonar
Making a ______ shaped ice cube involves running water over an evaporator plate in which the copper evaporator tubing is soldered onto the plates at regular intervals.
cresent
In order to keep dry ice in the soild form, the temperature of its surroundings can be _____.
a. 30 F
b. - 41 F
c. -100 F
d. -125 F
D
Nitrogen changes from a liquid to a vapor at ______.
a. 212 F
b. -21 F
c. -320 F
d. - 479 F
C
Cold plates are usually filled with a ______.
a. Brine solution
b. Eutectic solution
c. Sodium chloride or calcium chloride solution
d. All of the above
D
Dry ice is composed of ______.
a. Liquid nitrogen
b. Liquid carbon dioxide
c. Solidified carbon dioxide
d. Solidifed ammonia
C
A eutectic solution is a ______.
a. Phase change solution
b. Very warm solution
c. Acid solution
d. Explosive solution
A
In some applications of truck refrigeration, a liquid refrigerant is sprayed directly into the truck box to maintain low temperature. The liquid refrigeratn used is ______.
a. Oxygen
b. Nitrogen
c. R22
d. Ammonia
B
Truck refrigeration systems are designed to have the capacity to _____.
a. refrigerate a load that is not down to temoperature
b. refreeze a load that has thawed
c. hold the load temperature when in transit
d. All of the above
C
Where are cascade systems primarily used?
a. Extra low temperature
b. Low temperature range
c. Medium and low temperature
d. Medium temperature range
A
Ammonia is extremely toxic to humans and must be used with care. When working with ammonia systems it is often necessary for the technician to wear ____.
a. Google
b. Breathing apparatus
c. Protective clothing
d. All of the above
D
Seawater cooled condensers for marine use have ______.
a. Removable water box cover
b. Water circulating in the tubes
c. Tubes that are accessible for cleaning using a brush
d. All of the above
D
Water cooled condensers using sea water are usually designed and built to permit periodic cleaning by ______.
a. Brushing the tubes
b. Acid treatment
c. Back finishing
d. All of the above
A
T/F Because of the large capacities of refrigeration systems installed in trucks, the trucks themselves do not need to be insulated from outside ambient temeprature.
F
T/F Refrigerated trucks are equipped with systems that are designed primarily to maintain a products temperature while being transported.
T
T/F In a cascade system, the condensing rerigeratn in one stage is used to evaporate the refrigerant in another stage.
T
T/F At extremely low evaporator temperature, the compression ratio for the compressor becomes too great for single stage refrigeration.
T
T/F The axle driven refrigeration unit is a new system very commonly used in todays railway refrigeration.
F
T/F Cargo ship refrigeration units are usually sized with very little reserve capacity.
T
Refrigeration systems that use nothing more than a thermostatically controlled solenoid vavle feeding a distribution system can use _____ or carbon dioxide as their refrigerant.
Nitrogen
The process where a solid changes directly to a vapor without first becoming a liquid is called ______.
Sublimation
A system that uses two or more refrigeration systems working at the same time and exchanging heat between them to produce ultra low temperature is called a _____ system.
Cascade
The blast freeze method is done at very low temperature and a high air ________.
Velocity
Nitrogen is not suitable breathing because it has no ________ in it.
oxygen
The system of shipping refrigerated trucks loaded on railcars is known as ________.
Piggy back
When products need to be cooled during flight, ice or _______ is used.
Dry ice
