A.Vapor pockets formed in the suction flow stream
B.Rough easing volute surfaces
C.Worn wearing rings
D.Heavy fluid in the flow stream
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A.primarily to lubricate the shaft seals
B.due to the inability of this type of pump to lift water to cover the suction (eye) of the impeller
C.to initially unload the pump by having its head pressure equal to discharge pressure
D.in order to overcome the potential energy of water in the discharge line
A.humidification
B.dehumidification
C.vaporization
D.evaporation
A.latent heat of vaporization
B.sensible heat
C.refrigerating effect
D.specific heat of vaporization
A.Ball float
B.Thermostatic
C.Bimetallic
D.Impulse
A.a gas mask suitable for protection against each refrigerant used, or a self contained breathing apparatus must be provided
B.it is the sole responsibility of the chief engineer to ascertain that all members of the engineering department are familiar with the use of gas masks or breathing apparatus
C.spare charges shall be carried for at least 50% of each size and variety of gas masks and/or self contained breathing apparatus
D.all of the above
最新試題
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
A salinity indicator is used to determine the （）.
Which of the listed pumps is NOT a positive displacement pump?（）
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
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?（）
The output volume of a positive fixed displacement pump can be changed only by （）.
Thermostatic expansion valves can be adjusted for （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）