分段除霜持续供热空气源热泵系统除霜性能研究

DEFROST PERFORMANCE STUDY OF CONTINUOUS HEATING AIR SOURCE HEAT PUMP SYSTEM WITH SEGMENTED DEFROST

基于可持续供热空气源热泵热气旁通除霜技术,该文提出一种分段除霜持续供热空气源热泵系统,并在焓差实验室中对其进行性能研究。结果表明,环境温度或相对湿度降低,或冷凝温度升高均会使得分段除霜系统平均制热功率降低。分段除霜过程中的压缩机吸气压强变化幅度比逆循环除霜小698.5 kPa、排气压强变化幅度比逆循环除霜小238.9 kPa。自上而下的除霜顺序每段除霜用时依次增加,而自下而上的除霜顺序每段除霜用时基本相同,且自下而上的除霜顺序比自上而下的除霜顺序总除霜时间减少55 s,但会对“二次结霜”造成影响。与传统逆循环除霜系统相比,该分段除霜系统具有除霜时间短且可持续供热、COP高、对系统冲击较小等优点。但除霜期间由于阀门的切换,会引起系统局部压力波动和能量损失,有待进一步优化。

Based on continuous heating air source heat pump hot gas bypass defrost technology,this study proposes a segmental defrosting continuous heating air source heat pump system and investigates its performance in an enthalpy difference lab.The results show that lower ambient temperature or lower relative humidity or higher condensing temperature will reduce the average heating capacity of the segmental defrosting system.The change of compressor suction pressure in the process of segmental defrosting is 698.5 kPa smaller than that of reverse cycle defrost,and the change of discharge pressure is 238.9 kPa smaller than that of reverse cycle defrost.The defrosting sequence from top to down takes more time for each coil,while the defrosting sequence from down to top takes basically the same time for each coil,top to down defrosting sequence reduces total defrosting time by 55 s compared to top to down defrosting sequence,but has an impact on“secondary frosting”.Compared with the traditional reverse cycle defrost system,the segmental defrosting system has the advantages of short defrosting time and continuous heating,high COP,and less impact on the system.The switching of valves during defrosting will cause some local pressure fluctuations and energy loss in this system,which needs to be further optimized.