Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）

Low compressor head pressure in a refrigeration system can be caused by（）.

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

A salinity indicator is used to determine the （）.

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

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 （）.

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

Which of the following statements is correct concerning heat transfer?（）

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