Compressor lubrication is a problem frequently encountered in the design of refrigeration units. Under low load conditions the lubricant added to the circulating refrigerant accumulates in bends or pockets in the line between the compressor and the condenser and also in the suction lines where the refrigerant flows as a vapor. This can decrease the oil level in the crank-case of the compressor to a level where sufficient lubrication is endangered. A better understanding of the mechanism of the oil transport by the refrigerant vapor would permit a more reliable and less expensive design of refrigeration units.

Experimental data must be taken to describe the nature of this phenomenon. Also, analytical correlations are needed which can predict results. Specifically, information is needed on such things as pressure drop, liquid flow rate, void fraction and minimum velocity required to transport a given flow rate at a given condition.

This paper describes an initial investigation into this problem. A literature survey is given first. This serves to document, for the first time, information relevant to the problem. Secondly, an analytical model is chosen that can be used to characterize the flow. This is basically an annular two-phase flow model. Its adaptation to oil-refrigerant mixtures is discussed. A concluding section summarizes data requirements and outlines how the results will be used to test the theory.