Experimental study on flooding and flow reversal in small diameter tubes with various inclinations and horizontal lengths

Lubricant oil return to compressor in household refrigerator is controlled by oil-refrigerant two-phase flow behavior in the suction pipe. Conditions of flooding and flow reversal were considered as a conservative bound for the oil return. Phenomena associated with counter current flow limitation (CCFL or flooding) and flow reversal were experimentally investigated using small diameter tubes with vertical, inclined and crank-type configurations. Flooding and flow reversal phenomena were visually observed. Both flooding and flow reversal points were measured using various shapes of test section in a wide range of liquid flow rate. The gas velocities for flooding were found to be inversely proportional to the liquid flow rates and independent of the tube configurations. The gas velocities for the flow reversal point appeared to be at a similar level over a certain range of liquid flow rate but strongly depend on the inclination angle, horizontal length and kind of liquid.