单项选择题If the head pressure of a reciprocating refrigeration compressor is excessive, ().

A.the relief valve should open before the high pressure cutout
B.the relief valve should open and allow the excess refrigerant to flow to the receiver
C.the high pressure cutout switch should operate before the relief valve opens
D.you should close in on the suction valve


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1.单项选择题A salinity indicator is used to determine the ().

A.cause of salt contamination
B.location of salt water contamination
C.chemical makeup of feed-water
D.level of alkalinity in condensate

2.单项选择题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

3.单项选择题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

4.单项选择题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

6.单项选择题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

7.单项选择题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

8.单项选择题A salinity indicator is used to determine the ().

A.cause of salt contamination
B.location of salt water contamination
C.chemical makeup of feed-water
D.level of alkalinity in condensate

9.单项选择题If the suction pressure at the refrigeration compressor is below normal, the cause can be().

A.refrigerant overcharge
B.overfeeding by the expansion valve
C.a restricted suction strainer
D.due to short cycling of the compressor

10.单项选择题If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump ().

A.capacity will increase
B.capacity will decrease
C.suction pressure will increase
D.suction pressure will decrease