Experimental evaluation on the oil influence in capillary tubes

This work presents the results of an experimental study on pure refrigerant R-134a and refrigerant–oil mixtures flowing through capillary tubes in order to analyse the oil influence in component performance. Tests were carried out for capillary tubes internal diameters of 0.69 mm and 0.82 mm, condensing temperatures ranging from 40 °C to 50 °C, and subcooling degrees between 3 °C and 12 °C. Pure refrigerant flow measurements were compared to those for refrigerant–oil mixtures with oil concentrations of 1.0% and 3.0%.