In an air-conditioning or refrigeration system, a small percentage of the lubrication oil migrates out of the crankcase and into the working fluid. Two main concerns associated with this phenomenon are what is the effect of this oil on the pressure drop in the system and under what conditions is the oil reported back to the compressor? Both questions have direct relationship to the sizing of components and the efficiency of the unit. In relation to the second question, a deficiency of oil in the crankcase will eventually cause the system to shut down because of lack of lubricant.

With regards to suction and discharge lines, this subject has been addressed by and ASHRAE-sponsored research project which has now been completed (RP 109). Initial pressure drop results have been presented and oil transport result summarized in earlier publications. In the former paper, horizontal R-12 and 150 SS oil data were correlated. It is the purpose of this paper to report pressure drop results for vertical configurations as well as for R-22 and 300 SUS oil. In addition, sufficient documentation will be presented so that the correlations can be used by practicing engineers and design data will be given in tabular form.

The experimental facility will be discussed first, followed by an explanation of empirical relationship and correlated results.