單項(xiàng)選擇題When normal operating pressure is applied to the hydraulic oil used in a high-pressure system, the oil （）.

A.viscosity will decrease
B.volume will increase
C.volume will decrease
D.pour point will be reduced


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1.單項(xiàng)選擇題If the refrigeration compressor crankcase is sweating, the cause may be due to （）.

A.a shortage of refrigerant
B.the compressor running continuously
C.liquid refrigerant returning to the compressor
D.the compressor short cycling on the high pressure cutout

2.單項(xiàng)選擇題The primary reason low pressure evaporators produce distillate more efficiently, and with less scale formation, than high pressure evaporators is （）.

A.evaporation is accomplished in a vacuum
B.due to the higher temperature of the incoming feed
C.due to the latent heat of evaporation principle
D.evaporation in a submerged medium produces more distillate

4.單項(xiàng)選擇題Less scale formation occurs in a flash evaporator than in a submerged tube evaporator because （）.

A.the distillate produced has greater purity
B.no boiling occurs on heat transfer surfaces
C.evaporation occurs at a higher rate
D.the incoming feed is at a higher temperature

5.單項(xiàng)選擇題A liquid sight flow indicator in a refrigeration system is examined and gas bubbles are noted in motion with the fluid flowThis means （）.

A.the system is fully charged
B.there is air leaking in from the condenser
C.ice crystals are forming in the refrigerant
D.the system contains less than a full charge of refrigerant