A DISTRIBUTED MODEL FOR PREDICTION OF THE TRANSIENT-RESPONSE OF AN EVAPORATOR

A distributed parameter model for predicting the transient performance of an evaporator is presented. The model is capable of predicting dis tributions of the refrigerant velocity, void fraction, temperature, tu be wall temperature, air temperature and humidity, in both position an d time domains. An efficient and stable two-level iteration method is proposed to obtain the numerical solutions of the model without solvin g a large set of non-linear equations simultaneously. The dynamic beha viour of the evaporator is investigated with a step change in the inle t refrigerant flowrate. Comparisons are made with experimental measure ments on a commercial evaporator with refrigerant R134a as the working fluid. The results indicate that the model provides a reasonable esti mation of the dynamic response compared with the experimental data. It is also observed that the evaporator thermal response is faster for a step decrease than for a step increase in refrigerant flowrate.