單項(xiàng)選擇題

What is a function of the wearing rings used in most centrifugal pumps?（）

A.Absorb erosion of high velocity discharge stream
B.Seal pump shaft against entry of air
C.Isolate the discharge side from the suction side
D.Dampen the turbulent discharge flow

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單項(xiàng)選擇題

If air at 95℃ dry bulb temperature and 50% relative humidity is conditioned to 75℃ dry bulb temperature and 50% relative humidity, it is an example of （）.

A.cooling only
B.cooling and humidifying
C.cooling and dehumidifying
D.adiabatic cooling

單項(xiàng)選擇題

Which of the following descriptions best identifies the operating principal of a flash-type evaporator?（）

A.Sea water is heated to boiling temperature while under a vacuum
B.Sea water is passed over heated plates in a thin film
C.Heated sea water is injected into a vacuum chamber
D.Sea water is forced through a heated eductor