How Does Oil Fouling Affect An Air Conditioning or Refrigeration Operating System?

In virtually all air conditioning and refrigeration systems, 1/2% to 8% of the compressor's lubricating oil circulates with the refrigerant, this oil attaches to the inner walls of the refrigeration tubing and acts as an effective insulator to heat exchange.

It matters little whether the refrigerant is miscible or immiscible with the oil and oil seperators are ultimately overcome; contaminating oil films are deposited throughout the system in any case, and it is these oil deposits that ultimately cause block heat transfer and reduce system efficiency as reported by ASHRAE.

* 1986 ASHRAE Handbook, Refrigeration, Chap. 3.6