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

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

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 （）.

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 （）.

A salinity indicator is used to determine the （）.

A pressure drop through the refrigerant liquid line may cause （）.

When the steering gear is in operation, you should （）.

The major source of chemical contaminants in hydraulic fluid is （）.