Heat pump dryer is a complex system because of the interaction of heat and mass transfer of the working fluids. Since the system cannot be completely close, ambient conditions (temperature and humidity) influence the performance of the system. To investigate the performance of the heat pump dryer thoroughly, simulation models of heat pump dryer components have been developed. The finite-difference method was employed in the simulation to examine the state of the working fluids and heat and mass transfer. The simulation of each component can be used to construct different system configurations the results of which are reported in Part 2. KEY WORDS heat pump; heat pump model; heat pump dryer; heat pump simulation 1 4 H . O kg k Wh-' with an average of about 2.CL2.5 kg k W -' h-' (Hodgett, 1976). The latent heat of water is equivalent to an SMER of 1.56 kg k W -' h-'. A comparison of vegetable drying by the H P D and a conventional dryer using an electrical heater found that an energy saving of 40% can be made and the processing time reduced by 407% (Rossi et al., 1992).
The heat pump air dehumidifier coupled with a dryer is a complex system since all the components are interdependent. Any change in one component will inevitably influence the others. The change to the dryer itself is dynamic, thus adding a transient-behaviour problem to the experiment. Slow response time to changes in heat exchanger-type components results in difficulty in data interpretation. Studies of HPDs by computer simulation have received attention in recent years. In the study of Zylla et al. (1982), the H P D system was considered as a controlled volume where the balance of heat and mass was simulated. The simplification of the HPD model required many assumptions that might not be valid, for example the coefficient of performance (COP) was assumed as high as 1057 times that of a Carnot cycle. In addition, the temperature difference between the outlet air and the heat exchanger surface (condenser and