自然复叠式热泵循环系统热力性能分析

Thermal performance analysis of auto-cascade heat pump circular system

受热源温度以及系统本身性能的限制,目前应用较为成熟的单级蒸气压缩式热泵系统的出水温度一般在50℃左右,这种热泵系统已经无法满足对热源侧和使用侧有较大温差要求的场合,新的自然复叠式热泵系统能够实现大温差热泵循环,可以作为冬季高温热泵使用。在设计自然复叠式热泵循环、选择适合该系统运行的非共沸混合工质的基础上,对该热泵循环系统进行了不同条件下的数据计算和热力性能分析。理论分析结果显示: R134a充注浓度的增加将引起吸气压力和排气压力升高,且浓度增加过程中COP存在一个最大值、压比存在一个最小值;最低冷凝温度和最低蒸发温度一定时,排气压力和循环充注浓度基本呈线性关系。

By the limit of heat source temperature as well as system performance,outlet water temperature of single-stage vapour-compression is generally around 50℃.No way to be satisfied with the occasions in which large temperature difference is requested does this heat pump have.Large temperature difference can be achieved by auto-cascade heat pump system.Data computation and thermal energy performance analysis are carried on this cycle system,on the basis of the design of the system and the choice suits the system operation in non-azeotropic mixture foundation.Theoretical analysis shows that the suction and exhaust pressure will increase with R134a filling concentration charges.A maximum value of COP and a minimum value of pressure ratio appear with the increase of the concentration.Linear relationship of the exhaust pressure and the filling concentration,basically,is assumed condensing the lowest minimum and vaporization temperature is certain.