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 distributions of the refrigerant velocity, void fraction, temperature, tube wall temperature, air temperature and humidity, in both position and time domains. An efficient and stable two-level iteration method is proposed to obtain the numerical solutions of the model without solving a large set of non-linear equations simultaneously. The dynamic behaviour of the evaporator is investigated with a step change in the inlet refrigerant flowrate. Comparisons are made with experimental measurements on a commercial evaporator with refrigerant R134a as the working fluid. The results indicate that the model provides a reasonable estimation 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.