Question and answer Flashcards
#70 most compressors are positive displacement machines name a compressor that is not a positive displacement machine
D
Centrifical
#71 The ratio of the actual volume of refrigerant Vapor pumps to the theoretical displacement volume is known as
A
Volumetric efficiency
#72 air compressor in which the compressor and motor are both sealed within the same pressurizing housing is known as a
C
Hermetic compressor
#73 the passage of liquid refrigerant through the compressor suction and discharge valve should be avoided and is known as
B
Slugging the compressor
#74 modern high speed reciprocating compressors typically
D a+b
A= 1750 RPMs partially correct there is another common speed also
B= 3450 RPM partially correct there is another common speed as well the 1750
#75 Compressor capacity decreases as
D all above
discharge pressure increases suction pressure decreases compressor speed decreases
#76 an advantage of the
D all above
smooth quiet operation low torque variation through overlapping compression Cycles you moving parts
#77 how can you identify reverse
D a+b
the compressor will not compress the compressor will Stop on motor overload
#78 during scroll compression
A
refrigerant Vapor enters from the outside of the scroll and exits at the center
#79 capacity control on a helical rotary compressor is obtained using(screw type)
D
a sliding valve
#80 the screw type impellers used in a helical rotary compressors are also known as
A
Rotors
#81 the component in a centrifugal compressor that actually does the compressing is known as
A
An impeller
#82 a centrifugal compressor controls capacity through the use of
D a+c
variable speed and Vortex dampers
#83 bearings in a centrifugal compressor can be checked by
C
checking the temperature of the oil returning from the bearing
#84 a small access valve which is similar to the air valve used on tires is known as
B
Schrader valve
#85 a valve used to prevent flow of liquid refrigerant to the evaporator and to avoid flood back to the compressor during off Cycles is the
D
Solenoid valve
#86 a special value used to prevent evaporator temperature from falling below a predetermined minimum temperature regardless of suction pressure is the
A
Evaporator pressure regulator
#87 a metering device with the characteristic of feeding liquid into the evaporator at the same rate at the liquid flows from the condenser is the
B
high side float valve this valve consists of a float in a needle valve which creates the pressure drop separating the high side from the low side of the system as a liquid level from the condenser raises the flow Rises and opens needle valve forcing refrigerant into the evaporator . As the liquid level from the condenser drops the float drops also and closes the needle valve restricting the flow to the evaporator
#88 in a thermostatic expansion valve three forces act on the diaphragm in the powerhead which is connected to the valve evaporator pressure acts too ......., the spring pressure acts too .......... and the bulb pressure attached to the evaporator Outlet, acts to ....... the valve
B
close close open
#89 metering device that actually measures temperature rather than pressure or liquid levels is the
D
Thermal electric valve
#90 suction Line Filter drier should be installed whenever
C
a hermetic compressor motor burnout has occurred
91
filter dryers, and dryers
are filled with a material that is able to catch and retain moisture and acid This material is called?
B
Desiccant
92
suction Line Filter driers are usually equipped with Gauge connections so that pressure drops can be determined.
Why?
D
so that you can determine when to change the filter drier.
93
in general the greater the number of rows in an evaporator……………
.
……………………………..
D all above
the more closely the leaving air temperature will be to that of the refrigerant the, the more dehumidification
can take place, The colder the leaving air will be. To
#94 increasing airflow over an evaporator
A
increases evaporator capacity
#95 capacity control of a lithium bromide water absorption machine is accomplished
B
by controlling the heat input to the generator,
more heat results in an increased amount of refrigerant boiled out of the solution in the generator,
Creating more Refrigeration effect. Less heat results in less Refrigeration effect
#96 crystallization may occur in a lithium bromide water absorption chiller
D all above
if power fails while the machine is under a heavy load, if condenser water is allowed to get too cold, If the machine over cools during a shutdown period.
#97 the heat source for absorption liquid chillers could be
D all above
solar panels, Steam, hot water.
#98 The Purge units on absorption liquid chillers are designed to
C
expel non-condensable gases
#99 a possible cause for high head pressure is
D all above
dirty condenser tubes cause a reduction in the ability of the condenser to reject heat resulting in higher condensing temperatures and pressure,
insufficient water flow through the condenser reduces the ability of the condenser to reject heat resulting in higher pressure and temperature,
air and non condensables in the condenser
#100 approach temperature is the difference between
A
condensing temperature and leaving water temperature
#101 Gpm=btuh/500×TD TD=total difference
1.5gpm=15000btuh/500×TD(20°f)
#103 what are the products of perfect combustion using oxygen and a hydrocarbon fuel
B
carbon dioxide, heat,water
#104 describe the appearance of a properly adjusted natural gas flame in an atmospheric burner
C
study blue flame with a smaller lighter blue inner cone, resting on the burner
Port
#105 radiant tubing or piping should be pressure-tested to at least ................times expected operating pressure
B
2 times
#106 when filling a radiant heating system, it is recommended to fill
C
slowly from the low point so that the tendency for air pockets to form is reduced
#107 infrared heaters use burning gas to heat a specific radiant surface instead of using the infrared energy from the Open Flame because
A
heated surfaces are better heat radiators than open flame
#108 High efficiency (condensing) furnaces achieve and efficiency of up to 95% by
B
cooling the exhaust gases to below dewpoint and recovering some of the latent heat of condensation
