On the steady-state modelling of a two-stage evaporator system

We develop and validate against experimental measurements a steady-state tw o-stage flooded refrigerant evaporator model for a heat pump drying system. A prototype two-stage heat pump dryer test facility was designed, built an d instrumented to provide the required measurements for the validation of t he model. Repeatability and data quality tests were conducted to evaluate t he accuracy of measurements. Experimental data could be reproduced to withi n +/- 6.5 per cent of replicated air and refrigerant side measurements for the same evaporator's air inlet conditions while the discrepancy of energy balance at the air-side and refrigerant-side was observed to be within +/- 8.9 per cent. The two-stage evaporator model predicted the air-side total h eat and latent heat transfer of the two-stage evaporator to within (-6.3 pe r cent, 7.6 per cent) and (-11.5 per cent, 9.5 per cent), respectively. On the refrigerant-side, the model enabled the calculation of the degree of su perheat to within (-10.6 per cent, 1.7 per cent). The model has shown that there is significant improvement in the heat recovered from a two-stage eva porator system compared to a single evaporator system. In addition, the mod el demonstrated that the improvement in total heat recovery could be as hig h as 40 per cent over its base-value when the latent to total load at the t wo-stage evaporator is increased. Copyright (C) 2001 John Wiley & Sons, Ltd .