A generalized continuous empirical correlation for predicting refrigerant mass flow rates through adiabatic capillary tubes

Refrigerant flow through a capillary tube is complicated, and many empirical correlations have been proposed for calculating the refrigerant mass flow rate through capillary tubes. A common disadvantage of most previous empirical correlations is a discontinuity at the saturated liquid or saturated vapor lines. In the present study, a generalized continuous empirical correlation is developed that can be used to predict the refrigerant mass flow rate through a straight adiabatic capillary tube, for all capillary tube inlet conditions. The present empirical model was validated against experimental data available in the literature for R-12, R-22, R-134a, R-152a, R-404A, R-407C, R-410A, R-507A, and R-600a, covering subcooled and two-phase mixture inlet conditions. This correlation can be applied in refrigeration simulation tools to reduce runtime, and enhance the accuracy of refrigerant mass flow rate predictions for a wide range of refrigerants.