Heat pump air conditioning system's (HPAC'S) performance enhancement was analyzed by means of simulation for 10 m pure electrical bus. The steady-state simulation model of HPAC was constructed, which was corrected and verified by the experimental data. The heat transfer coefficient increased because of the decrease of heat exchanger's diameter of the tube. Tube-fin heat exchanger with φ 5 mm diameter tube was designed to the new HPAC and new design's effect on system performance was simulated by verified simulation model. The cooling (heating) capacity was 23.2 kW (20.9 kW), and cooling EER (heating COP) was 3.14 (2.75). New HPAC's performance was improved, but couldn't meet improvement target. The simulation results showed that system's mass flow rate was lower than design value, and the compressor capacity was smaller than system requirement. The high efficiency scroll compressor not only increased the displacement, but also the cooling COP of the compressor was 3.45. The combination of the two factors improved the HPAC's energy efficiency. A high efficiency R410a scroll compressor was selected and applied to the same HPAC with the small diameter tube heat exchanger. The simulation results showed that cooling (heating) capacity reached to 26.4 kW (23.4 kW), while cooling EER (heating COP) reached to 3.64(3.16), which generally met design requirement that cooling (heating) capacity reached to 26 kW (22 kW), while cooling EER (heating COP) reached to 3.2(2.8).
HAN Lian-jin, WU Jiang-hong, XUE Zhi-qiang. Simulation and improvement of heat pump air conditioning system for electric bus. JOURNAL OF ZHEJIANG UNIVERSITY (ENGINEERING SCIENCE), 2018, 52(4): 641-648.
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