An improved method for analyzing a fin and tube evaporator containing a zeotropic mixture refrigerant with air mal-distribution

Abstract

A new program was developed to analyze the heat transfer characteristics of fin and tube evaporators that use a zeotropic mixture refrigerant, R-407C, as the working fluid. The calculation algorithm is based on EVSIM (NIST), but a tube is segmented into several sections to provide a base unit for the calculations in this study. Therefore, two-dimensional air mal-distribution in the tube-length (horizontal) and vertical directions of the evaporator can be considered. The temperature gradient in the flow direction is traced using a discrete pattern to simulate the continuous variation found in actual evaporators. To validate the simulation results, 45 test cases in a real evaporator were performed with two different refrigerant flow path configurations using R-22 and R-407C refrigerants. The deviation between the simulations and test data was a maximum of 5.4%, and the trends were similar. The local heat transfer predictions were verified by comparing the numerical and test wall temperatures along the refrigerant flow path. Local temperature difference and the heat transfer contributions from each row are also analyzed along refrigerant flow path. And more, the impact of air mal-distribution is studied with two-dimensional four different types of velocity profiles and the significant difference in heat transfer is analyzed. The program developed in this study will be a useful tool to know all of information related with heat and mass transfer at any local point and can be used for improving the efficiency of zeotropic mixture refrigerant evaporators. (C) 2003 Elsevier Ltd and IIR. All rights reserved.