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10 Cards in this Set
- Front
- Back
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The most widely used refrigerant control which consists of a bellows or a diaphragm chamber connected to a temperature sensing bulb by means of a small capillary tube is a/an
a) thermostatic expansion valve b) automatic expansion valve c) low pressure float valve d) hand operated expansion valve e) high pressure float valve |
A
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Which of the statements about automatic expansion valves is false? a) The valve maintains constant pressure in the evaporator during compressor operation regardless of the load. b) When the compressor stops the valve automatically shuts off. c) A spring exerting a downward force on the diaphragm tends to open the valve. d) The spring force is countered by evaporator pressure acting downward against the diaphragm which closes the valve. e) The control may be used with multiple cooling coils connected to the same compressor. |
E
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Which control is used to maintain a constant level of liquid refrigerant in a flooded evaporator in the liquid reserve tank? a) thermostatic expansion valve b) automatic expansion valve c) low pressure float valve d) hand operated expansion valve e) high pressure float valve |
C
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The simple control which restricts the flow of liquid from the condenser to the evaporator and maintains a pressure difference between the two units by using a considerable pressure drop resulting from resistance between the devices length and small bore is called a) a high pressure float valve b) a low pressure float valve c) a bypass line d) a capillary tube e) an external float chamber |
D
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In a system controlled by a high pressure float valve insufficient liquid will cause which of the following results? a) automatic system shut down b) boosting the compressors pressure c) liquid being carried over to the compressor with the vapour d) starving the evaporator and reducing the capacity of the system e) all of the above |
D
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One method of controlling the capacity of reciprocating compressors is to bypass the discharge from one or more cylinders back to the suction side of the compressor. The control is called a) compressor unloading b) dampering c) suction throttling d) cylinder bypass e) sectional evaporating |
D
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Sectional evaporators control the capacity of the evaporator by which of the following means? a) Varying the quantity of air being cooled passing over the evaporator coils. b) Intermittent operation of the compressor. c) Divided multipart evaporators which have refrigerant control valves which can be shut off independently as the load decreases. d) Switching gears in the compressor. e) Decreasing suction in the compressor. |
C
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Which of the following statements about evaporator dampers is true? a) These dampers decrease the resistance to the passage of air. b) When the damper is closed the quantity of air passing over the evaporator coils is at a maximum. c) Depending on the damper position the quantity of air passing through the duct varies widely. d) Multispeed blowers cannot be used in combination with evaporator dampers. e) None of the above. |
E
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The type of operation which stops the compressor when the desired low temperature of the substance to be cooled is reached and starts the compressor up again when the temperature rises to a set level is called a) intermittent operation b) continuous operation with reduced output c) cylinder bypass operation d) unloading operation e) variable guide operation |
A
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The control which is replacing suction throttling and operates by swirling the refrigerant in the same direction as the compressor impeller, resulting in a reduction of power required by the compressor is which of the following controls? a) Hot gas bypass b) Cylinder bypass c) Variable Inlet Guide Vanes d) Damper control e) Compressor unloader |
C
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