内部换热器对三级复叠式制冷系统性能影响的热力学分析

Effects of Internal Heat Exchanger on Performance of Three-stage Cascade Refrigeration System

为研究内部换热器对三级复叠式制冷系统性能的影响,本文以采用制冷剂组R1150/R170/R717与R50/R170/R717的三级复叠式制冷系统为研究对象,将带有低温级内部换热器、中温级内部换热器、中低温级内部换热器的三级复叠式制冷系统和无内部换热器的制冷系统对比分析。分析结果表明:当蒸发温度为-120℃^-80℃,无内部换热器时,制冷剂组R1150/R170/R717的COP高于R50/R170/R717系统。在有内部换热器的系统中,对于R1150/R170/R717,内部换热器的使用均不利于提高COP,但是仍高于R50/R170/R717系统的COP。当蒸发温度为?100℃时,相比无内部换热器的系统,带有中温级内部换热器、低温级内部换热器、中低温级内部换热器的三级复叠式制冷循环的COP分别降低0.57%、1.53%和3.58%。对于R50/R170/R717,中温级内部换热器的使用均使COP降低,低温级内部换热器的使用只有在蒸发温度为-115℃^-100℃时才有利于提高系统COP,但提高幅度不到1%。因此当三级复叠式制冷系统使用R1150/R170/R717和R50/R170/R717时,不推荐使用内部换热器。

In order to explore the effect of internal heat exchanger(IHX)on the performance of three-stage cascade refrigeration system(TCRS),taking the TCRS with refrigerant group R1150/R170/R717 and R50/R170/R717 as the research object,TCRS assisted with IHX in low-temperature cycle(CIL),TCRS assisted with IHX in medium-temperature cycle(CIM),TCRS assisted with IHXs in medium-temperature cycle and low-temperature cycle(CIL-M)and TCRS without IHX(C)were compared and analyzed.The results show that the COP of R1150/R170/R717 C is higher than that of R50/R170/R717 C when evaporation temperature(Te)is between-120℃and-80℃.For R1150/R170/R717,the use of IHXs is not conducive to the improvement of COP,but the COP of R1150/R170/R717 TCRS with IHXs is still higher than that of R50/R170/R717 TCRS with IHXs.When Te is-100℃,compared with C,the COP of CIM,CIL and CIL-M decrease by 0.57%,1.53%and 3.58%,respectively.For R50/R170/R717,the use of IHX in medium-temperature cycle reduces the COP,however,the use of IHX in low-temperature cycle can only improve the COP when the Te is between-115℃and-100℃,but the increase is less than 1%.Therefore,the use of IHXs is not recommended when R1150/R170/R717 and R50/R170/R717 are used in TCRS.