The output volume of a positive fixed displacement pump can be changed only by （）.

A grease gun is generally used to lubricate a （）.

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?（）

When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.

The usual symptoms of cavitation in a centrifugal pump is （）.

An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.

Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）

The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.

If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.