Investigation on advanced heat pump systems with improved energy efficiency

摘要

Centrifugal heat pumps with waste heat recovery have a bright application future in industry field due to their large heating capacity and high supply water temperature. Two kinds of advanced heat pump systems are proposed and analyzed to improve the energy efficiency. The system performances are analyzed and compared for three kinds of centrifugal heat pump systems: the one-cycle two-compressor system, two-compressor parallel system, and two-cycle parallel system. According to the simulation results, the two-cycle parallel system shows great advantages in the heating capacity, power capacity, and system COP (coefficient of performance). For 30 degrees C evaporator inlet water temperature and 60 degrees C condenser outlet water temperature, the COP improvements of the two-compressor parallel system and two-cycle parallel system are 7.7% and 15.5%, respectively. When the condenser outlet water temperature is 80 degrees C, the system COP of the two-cycle parallel system is 9.6% and 19.0% higher than that of the one-cycle two-compressor system with 30 degrees C and 60 degrees C evaporator inlet water temperatures. The COP of the two-compressor parallel system is 5.2% and 10.2% higher than that of the one-cycle two-compressor system under the same working condition. When the temperature lift is kept at 30 degrees C and the condenser outlet water temperature changes from 60 degrees C to 90 degrees C, the maximum and minimum COP of two-cycle parallel system are 6.7 and 6.1, respectively, which is at least 6.8% higher than the COP of the two-compressor parallel system and 13.5% higher than that of the one-cycle two-compressor system. The experimental validation is conducted, and the results indicate that the two-cycle parallel system can satisfy the high-temperature, large-capacity, and high-efficiency requirements for industrial applications.