A.pump must always be primed
B.volute must impart a radial and rotary motion of the water suction side
C.connection must guide the liquid to the lantern rings
D.stuffing box should not be allowed any water leakage
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A.change in impeller diameter
B.square of the impeller diameter
C.cube of the impeller diameter
D.impeller efficiency for large changes in the size of the impeller
A.the suction pressure to decrease
B.the suction temperature to increase
C.increased ice formation on the evaporator coil
D.excessive short cycling of the compressor
A.Lobe
B.Screw
C.Radial piston
D.Volute
A.They are particularly suited for pumping high viscosity fluids
B.They are started with the discharge valve opened
C.The flow of liquid is developed by imparting energy due to the rotation of an impeller
D.They are always mounted in a horizontal position
A.refrigerant pressure in the evaporator
B.cooling water temperature to the condenser
C.heat load in the refrigerator compartment
D.solenoid valve in the liquid line
最新試題
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
A pressure drop through the refrigerant liquid line may cause （）.
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
Thermostatic expansion valves can be adjusted for （）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.