单项选择题
Which of the following statements about pump operations is NOT a correct statement?（）
A.In order for a fluid to be pumped, a fluid must be made to flow
B.A substance must be cold in order for it to be pumped
C.The kinetic energy imparted by the pump can be used to force a liquid through a hydraulic system
D.A pump must receive its energy from an external source
相关考题
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单项选择题
Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be （）.
A.one size smaller than the pump suction nozzle
B.the same size as the pump suction nozzle
C.one size larger than the pump suction nozzle
D.installed with a short radius elbow at the pump -
单项选择题
In the operation of a flash type evaporator equipped with air ejectors,the air and non- condensable gases are evacuated directly from the （）.
A.first stage flash chamber
B.second stage flash chamber
C.first stage after condenser
D.second stage distilling condenser -
单项选择题
The refrigeration compressor in a water cooled refrigeration system is short cycling on the high pressure cutout switch， One reason for this could be the （）.
A.system is low on refrigerant
B.high pressure cutout switch is improperly adjusted
C.discharge valves are leaking slightly
D.discharge valves are leaking excessively
