Condensation heat transfer and pressure drop of oil-refrigerant-113 mixtures inside smooth and internally finned tubes

Heat transfer and pressure drop data were taken during condensation of Refrigerant-113 and 150-SUS naphthenic mineral oil mixtures inside smooth and internally finned tubes. Mixtures with oil concentrations of 1.2%, 2.8% and 4.0%, by weight, in addition to pure refrigerants, were tested. The data were collected from three sets of tube-in-tube, counter flow test condensers where test fluid condensed inside the inner tube and the cooling water flowed in the annulus. Each set had two condensers. Within each set, the inner tube of one of the condensers had internal fins on the inside while the other had a smooth surface. Both tubes had the same outside diameter. The inner tubes of the three sets differed in the outside diameters and the geometric parameters of the fins.;The data of pure refrigerants and oil-refrigerant mixtures were correlated with existing correlations and the best predictors of the data were identified.;An analytical model has been developed to predict the pressure drop during condensation inside longitudinally finned tubes. The model is capable of predicting the effects of changing the fin parameters, such as the number of fins, and the height and the width of the fin, on the condensation pressure drop. It can also predict the effects of changing the same parameters on the power demand per unit heat transfer.;The presence of oil resulted in a reduction in the heat transfer coefficient for both smooth and internally finned tubes. These reductions were approximately 7%, 12%, and 16% for oil concentrations of 1.2%, 2.8% and 4.0%, respectively, for both smooth and internally finned tubes. The heat transfer for both pure refrigerants and oil-refrigerant mixtures were enhanced by internal fins. This enhancement was in the range of 25-85%. Internal fins increased the pressure drop of both pure refrigerants and oil-refrigerant mixtures in the range of 75-480% over the smooth tube results. However, the presence of oil had little effect on pressure drop for all the tubes tested.