R290低压比热泵高补气过热度循环研究

Research on high injection superheat cycle for R290 low pressure ratio heat pump

天然工质丙烷(R290)GWP接近零,对环境友好,热物理性质优良,具有良好应用前景。高背压旋转压缩机运行压比小时,R290绝热指数小导致的排气温度低特点突出。R290在高背压旋转压缩机油池中溶解度大,R290/润滑油混合物黏度低,可能难以满足曲轴/轴承系统润滑,影响压缩机可靠性。通过研究低压比工况下,R290在润滑油中溶解度及R290/润滑油混合物黏度与其过热度的关系,提出高补气过热度经济器循环,利用冷凝器出口高温与补气饱和温度的温差带来的剩余热量提高补气过热度,从而控制排气过热度和R290/润滑油混合物的黏度。同时,高补气过热度经济器循环可以有效提高系统性能,蒸发温度-2.89℃,冷凝温度51.5℃时,相比单级循环,COP提升11.4%,单位容积制热量提升23.4%。

The natural working fluid propane(R290)has a GWP close to zero.It is environmentally friendly,has excellent thermophysical properties,and has good application prospects.The discharge temperature of R290 high-pressure rotary compressor is low due to the low adiabatic index of R290,especially in the small pressure ratio condition.The high solubility of R290 leads to the low viscosity of R290/lubricant mixture in the oil sump of high-pressure rotary compressor,which may be difficult to meet the crankshaft/bearings system lubrication and affect compressor reliability.This paper analyzes the relationship between R290 solubility in lubricant and viscosity of R290/lubricant mixture with mixture superheat in low pressure ratio condition.The high injection superheat cycle(HISC)is proposed that it takes advantage of the available energy in the condenser outlet to improve the injection superheat controlling the discharge superheat and the viscosity of R290/lubricant mixture.Meanwhile,HISC can effectively improve the system performance with 11.4%improvement in COP and 23.4%improvement in volumetric heating capacity compared with the single-stage cycle at evaporation temperature-2.89℃and condensation temperature 51.5℃.