Condenser coil optimization and component matching of heat pump dryer

The heat pump dryer is an energy- efficient piece of drying equipment, but due to its complicated system of the two interactive working fluids ( refrigerant and drying air), the optimum design remains the question. A heat exchanger is the major component influencing the heat pump dryer ( HPD) performance. This article reports a study to optimize the condenser coil of the HPD and the component matching in order to obtain optimum performance. The study was carried out by a mathematical model for system simulation and followed by experimental verification. Five HPD configurations were studied, including different designs in air and refrigerant flow paths. It was found that the closed- loop HPD with air bypassing over the evaporator is the most appropriate configuration. The proper coil design is 2- row, 2- circuit configuration with optimum refrigerant mass flow rate of 16 - 20 g/ s/ circuit. The optimum air flow rate was found to be in the range of 0.6 - 0.8 kg/ s. The corresponding number of coil modules is 8.