18 May 2002
A new heat pump drying method of applying CO2 transcritical process to the drying of biotechnology materials (seeds) is originally proposed in the paper. The method makes full use of the advantage of heat recovery in the cycle, and heat rejection process has a good temperature matching with drying medium (air). The paper presents a contrastive analysis of the coefficient of performance (COP) and the specific moisture extraction rate (SMER) of drying heat pump with CO2 and that with conventional working fluids R134a, NH3 and R12 under the same drying conditions. The results show that heat pump drying with CO2 transcritical process is superior to that with conventional working fluids, and is an environment-protecting, energy-saving and highly efficient method of drying seeds.