Comparison Among Different Methods for Predicting Mass Flow Rate of Refrigerant in Capillary Tubes

Abstract

Predicting of refrigerant mass flow rate in capillary tube is widely used in numerical simulation and designing of refrigeration and air conditioning systems, so the present study tries to compare the existing analytical and mathematical methods for predicting mass flow rate of refrigerant through capillary tube with experimental data published in previous studies. Assuming adiabatic, homogenous flow rate of refrigerant and neglecting the delay of vaporization region (metastable region) inside the capillary tube. The refrigerant R-22 is used in present study because of the wide range of experimental data and mathematical modeling methods that available.
Three mathematical methods for predicting and modeling mass flow rate in capillary tube were programmed and the results compared with experimental data available. A simple iterative indicator of chock flow condition at exit plane of capillary tube is used during calculations of element by element methods instead of tedious analytical equations. Generally the results show low values of predicted refrigerant mass flow rate compared with experimental data.
Element by element analysis method (present work) predicted mass flow rate with a mean deviation of 10.9% from the experimental data. Zhang and Ding [5] analytical method and Koizumi [1] method predicted mass flow rate with a mean deviation of 11.9% and 37.7% respectively.