Heat transfer and pressure drop of HFC134a-oil mixtures in a horizontal condensing tube

The paper reports the results of condensation heat transfer and pressure drop from tests with pure and oil-contaminated refrigerant HFC134a in a horizontal tube (10 m in length, 6 mm ID). The experimental results are compared with prediction from correlation. The heat transfer coefficient in the case of oil-contaminated refrigerant is shown to depend strongly on the definition of the saturation temperature. Using the pure refrigerant saturation temperature (hence disregarding the influence of oil on the vapour pressure), the results for average heat transfer coefficient show only minor effect of the oil contents. If the saturation temperature of the refrigerant—oil mixture is used, there is thus a significant degradation of the heat transfer coefficient (as expected) with increasing oil concentrations.