單項選擇題An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by ().

A.restriction in refrigerant piping
B.air and non-condensable gases in the condenser
C.water in the refrigerant
D.flooding back of liquid refrigerant from the evaporator


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1.單項選擇題Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?()

A.A shortage of liquid refrigerant
B.Excessive frost on the evaporator
C.Excessive condenser cooling water
D.Insufficient condenser cooling water flow

2.單項選擇題The general purpose of a heat exchanger is to ().

A.eliminate hot air from the condenser
B.maintain steady pressure in a system
C.heat, or cool one fluid by means of another fluid
D.reduce the engine room temperature in tropical climates

4.單項選擇題The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will ().

A.remain constant along the tubes length
B.be greatest in a single pass counter flow heat exchanger
C.remain constant throughout the heat exchanger
D.vary from section to section through out the heat exchanger

5.單項選擇題If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be ().

A.a low load on the unit
B.a clogged pump suction strainer
C.a blockage in the line between the pump and hydraulic motor
D.the hydraulic motor turning too fast