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

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

If the head pressure of a reciprocating refrigeration compressor is excessive, （）.

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

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

Thermostatic expansion valves can be adjusted for （）.

Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）

If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.

One cause of high head pressure occurring in a refrigeration system can be （）.

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