An empirical correlation and rating charts for the performance of adiabatic capillary tubes with alternative refrigerants

With the phaseout of conventional refrigerants, refrigeration and air conditioning systems must be redesigned to improve system performance and reliability with alternative refrigerants. In this study, a generalized correlation for the prediction of refrigerant flow rate through adiabatic capillary tubes is developed by generating dimensionless parameters for operating conditions, capillary tube geometry, and refrigerant properties using the Buckingham Pi theorem. The database for the present correlation includes extensive experimental data for R12, R22, R134a, R152a, R407C, and R410A obtained from the open literature. The present correlation, which has a relatively simpler form to employ, yields a mean deviation of 5.4% and a standard deviation of 6.5% from the database. In addition, rating charts for predicting refrigerant flow rate through adiabatic capillary tubes are generated for R12, R22, R134a, R152a, R407C, and R410A.