Experimental measurements of pressure drop have been made for forced-convection evaporation and condensation of oil-refrigerant (R-12) mixtures inside a horizontal tube, Data were compared to a wide range of frictional pressure drop and void fraction relationships. The best representations for the oil-free data were then modified to better correlate both oil-free and oilrefrigerant results. For condensation, a modification of the prediction given by the Lockhart- Martinelli relation for frictional pressure drop and the homogeneous void fraction model is presented. For evaporation, the prediction given by the Dukler II frictional pressure-drop correlation and the homogeneous void fraction is modified. These relationships predict the pressure drop for 85% of the data to within ±35%. The added oil increased the pressure drop 2% to 6% for condensation and 63% to 86% for evaporation.

Units: Dual