Numerical-based non-dimensional analysis of critical flow of R-12, R-22, and R-134a through horizontal capillary tubes

•Numerical analysis based on drift flux model on R134a, r12, and R22 critical flow.•Numerical data utilized to develop non-dimensional parameters and correlations.•General correlations developed to find critical mass flow rate and pressure.•Deviation of the correlation results from numerical results is less than 1%.•More exact results in comparison with available correlations.

Development of correlations predicting critical mass flow rate and critical pressure distribution through capillary tubes is presented. In order to accomplish such a work, the critical mass flow rate and pressure distribution for nearly 500 operational conditions for R-12, R-22, and R-134a are evaluated. Operational conditions include inlet pressure varying from 800 to 1500 kPa, inlet subcold temperature between 0 and 10 °C, length varying from 1 to 2 m, and inner diameter between 0.5 and 1.5 mm. By performing non-dimensional analysis on numerical data, general correlations are presented to predict the critical mass flow rate through capillary tubes. In addition, by utilizing numerical data for down-stream pressure, non-dimensional analysis is performed to present correlations to predict critical down-stream pressure and pressure distribution through capillary tubes.