The applicability and energy consumption of a parallel-loop exhaust air heat pump for environment control in ultra-low energy building

Abstract

• A novel inverter driven dual-cylinder rotary compressor was used. • The energy efficient working mode was proposed. • The system can well satisfy the requirements of building. A novel dual-cylinder rotary compressor was designed to improve the indoor space utilization, and it was used to drive a parallel-loop exhaust air heat pump (PEAHP) which integrates the functions of heating, cooling, ventilation and heat recovery. The operation characteristics of the system in different compressor frequencies and different fresh-air-to-return-air ratios (FRRs) were studied and analyzed experimentally. Through the simulation of the ultra-low energy buildings (ULEBs) in 12 cold zone cities, the hourly (8760 h) building thermal loads in the whole year are calculated. On the basis of the matching of the hourly system working characteristics and the thermal loads of ULEB, the energy efficient working strategy is proposed. Finally, the applicability and energy consumption of the PEAHP system applying in ULEBs were analyzed. The results show that, the system heating/cooling capacity and COP can be considerably improved by increasing return air volume flow rate. In winter, under the working condition of 50 Hz-FRR 1:1, the peak heating capacity and COP are 8.94 kW and 9.63, respectively, which are 77.38% and 64.05% higher than those when FRR is 1:0. In summer, when the outdoor temperature ranges from 26 °C to 40 °C, the system temperature effectiveness is higher than 1 in all working modes. The PEAHP system has great applicability for ULEBs in cold zone of China during winter, and the system can meet the year-round use demands of the ULEBs in Taiyuan, Dalian, Lanzhou, Yinchuan and Lhasa, with the unsatisfied heating/cooling time ratio of 1.61%, 0.09%, 0.006%, 2.45% and 0.02%, respectively.