The general purpose of a heat exchanger is to （）.

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

The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.

An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.

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

Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.

The rate of heat transfer from a hot region to a cold region is affected most by the （）.

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