Condenser, Evaporator, Metering Device Pretest Flashcards
Closing the condenser housing louvers can be used to raise low head pressure in low ambient temperatures
True or False
True
Some water defrost systems spray a lithium chloride brine solution solution over the evaporator
True or False
True
Some commercial refrigeration applications require that water be kept from freezing at temperatures below 32F
True or False
True
A fixed orifice metering device consists of a length of seamless tubing with a small and precisely formed inside diameter
true or false
false
systems equipped with a high-side float use a separate liquid receiver
true or false
false
A PWM solenoid EEV can hold its value at any variable position between open and closed for the purpose of modulating refrigerant
True or False
False
Hunting might allow liquid refrigerant to reach the compressor and cause compressor damage
True or False
True
In a system that uses a standard TXV, high-side and low-side pressures balance during the off cycle.
True or False
False
A TXV can adjust the refrigerant flow rate to compensate for varying loads
True or False
True
A filter-drier should be placed in the liquid line ahead of the TXV
True or False
True
Capillary tubes regularly function as check valves
True or False
False
A suction line-liquid line heat exchanger ______
a) superheats liquid refrigerant on the high side
b) superheated vapour refrigerant in the suction line
c) promotes a steady column of liquid in the suction line
d) all of the above
b)
A hot water reclaim tank is a cylinder filled with water that absorbs heat from refrigerant flowing through a refrigeration systems ________
a) discharge line
b) suction line
c) accumulator
d) sight glass
a) discharge line
Counterflow in a tube-within-a-tube condenser allows
a) the warmest water to be adjacent to the warmest refrigerant
b) the coolest refrigerant to be next to the coolest water
c) a steady transfer of heat throughout the entire condenser
d) all of the above
d) all of the above
A condenser in which a water tubing winds around the inside of a metal refrigerant shell is called a __________
a) air cooled
b) shell and coil
c) shell and tube
d) tube within a tube
b) shell and coil
Some types of water-cooled condensers use ________________
a) the top part of the shell as liquid receiver
b) bottom part of shell as liquid receiver
c) both and B
d) neither A or B
b) bottom part of shell
A condenser that uses only water as the medium into which system heat is expelled is a ________________
a) air cooled
b) water cooled
c) evaporative
d) all of the above
d) all of the above
In a hot-gas defrost system, the evaporator is defrosted by:
a) refrigerant from the vapour line
b) suction vapour from the low side
c) warm liquid refrigerant from the high side
d) hot exhaust fumes from a gas or diesel engine
a) refrigerant vapour from the discharge side
In what type of defrost system is hot refrigerant gas diverted to the evaporator to expedite the defrosting process?
a) off cycle defrost system
b) pump down defrost system
c) electric defrost system
d) none of the above
d) none of the above
Which of the following statements regarding off cycle defrost systems is FALSE?
a) frost accumulates during the on cycle
b) evaporator fans continue to circulate air during off cycle
c) the heat in the air circulated during the off cycle melts the frost
d) it can only be used in very low temperature systems
d) it can only be used in very low temperature systems
An electric heat defrost system ________
a) energizes electric heating coils
b) applies an electric voltage directly to the frost covered coil
c) used illuminated heat lamps
d) none of the above
a) energizes electric heating coils
Which of the following statements regarding water defrost systems is false?
a) water delivery may be dropped through a pan located over the evaporator
b) water delivery may be through a spray
c) water delivery may be done during a cooling cycle with the compressor running
d) the water running over the evap is warm enough to melt the ice
c) water delivery may be done during a cooling cycle with the compressor running
A condensate pump is used to __________
a) remove the moisture that builds up from defrosting and compensating
b) move water to a cooling towers gravity flow basin
c) provide water pressure for an evaporative cond
a)
A defrost timer that turns on defrost operations at a preset time and stops defrosting operations when the evaporator reaches a preset cut-out temperature is a _______________ defrost timer
a) time-initiated, temperature-terminated
b) time-initiated, pressure-terminated
c) time initiated, time-terminated
a)time initiated , temperature terminated
Surfaces in and along air ducts that direct air flow through the evaporator and throughout the cabinet are called;
a) off center plates
b) fittings
c) wet plates
d) baffles
d) baffles
Heat exchangers made from two metal sheets that are welded together to form a series of passages are ___________ evaporators
a) baffle-tube
b) fin-and-tube
c) plate
d) shell-and-sheet
c) plate
A liquid-cooling evaporator ____________
a) uses a cooled liquid that acts as the primary heat transfer medium
b) can be immersed or tube-within-a-tube
c) is designed to cool a liquid rather than air
d) all of the above
d) all of the above
An evaporator that depends on gravity for air circulation is a ___________ evaporator
a) forced-draft
b) natural-draft
c) quick-draft
d) all of the above
b) natural-draft
The function of EEV’s is to maintain _________ at a desired setting
a) superheat
b) sub cooling
c) ambient temperature
d) head pressure
a) superheat
On a cap tube system, severe frosting is the suction line during compressor start-up indicates a __________
a) overcharge
b) undercharge
c) refrigerant leak
d) none of the above
a) overcharge
Electronic expansion valves (EEV’s) use a _______ -operated assembly
a) spring
b) diaphragm
c) bellows
d) none of the above
d) none of the above
To maintain a constant pressure in the evaporator when the system is running, an AXV _______ refrigerant flow when the evaporator pressure drops
a) decreases
b) stabilizes
c) increases
d) none of the above
c) increases
Pulse width-modulating (PWM) solenoid EEV’s are refrigerant metering devices that use a pulse width modulation signal to control the operation of a _______ for variable refrigerant flow
a) stepper motor
b) diaphragm
c) solenoid valve
d) bleed valve
c) solenoid valve
Low-side float (LSF) metering devices control the flow of liquid refrigerant into the _________
a) sensing bulb
b) compressor
c) evaporator
d) suction line
c) evaporator
Increasing the ______ too much will starve the evaporator
a) superheat
b) sub cooling
c) undercooking
d) none of the above
a) superheat
The orifice size of a metering orifice may need to be changed for units with long _______ sets to account for the extra refrigerant charge
a) filter drier
b) suction line
c) piston
d) expansion
b) suction line
When a capillary tube serves the function of both the liquid line and the metering device, it is connected between the evaporator and the ___________
a) suction line
b) condenser
c) compressor
d) accumulator
b) condenser
The ________ of the cap tube determines how much pressure drops between the condenser and evaporator
a) length
b) inside diameter
c) number of turns
d) all of the above
d) all of the above
Metering devices that can change their orifice size to account for changes in cooling loads are referred to as ________ metering devices
a) modulating
b) flow
c) fixed
d) limited
a) modulating
The primary purpose of a metering device is to produce ________
a) pressure drop
b) temperature drop
c) sub-cooling
d) superheat
a) a pressure drop
