An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.

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

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

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

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

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

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

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

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

A salinity indicator is used to determine the （）.