液体旁通复叠式制冷系统性能分析

PERFORMANCE OF CASCADE REFRIGERATION WITH LIQUID REFRIGERANT BY-PASS

为调节应用于高低温恒温箱中的复叠式制冷系统的制冷量,提出液体旁通制冷系统。当旁通电磁阀关闭时,制冷系统处于最大负荷状态,而电磁阀开启后,通过蒸发器的制冷剂减少,制冷量减少。因此,可以根据低温下制冷量的要求,调节进入蒸发器的制冷剂流量,从而调节制冷量。根据有限时间热力学原理,对这种复叠式制冷系统建立数学模型,进行数值模拟,对数值解的分析,表明这种负荷调节方式是可行的。液体旁通复叠式制冷系统有效地降低了压缩机的排气温度,且不存在液击的危险,适合应用于高低温恒温箱中提供变负荷制冷量。对高低温恒温箱的性能测试表明,带有液体旁通的复叠式制冷系统能有效地减小系统在高温工况下的制冷量并节约能量。

To control refrigeration capacities of cascade refrigeration in high/low thermostat unit （HLTU）, liquid refrigerant by-pass is introduced. When the by-pass magnetic valve is close, refrigeration system is at its maximal capacity conditions; When the magnetic valve is open, refrigerant through evaporator decreases, which leads to the refrigeration capacity dropping. Therefore, HLTU system can adjust refrigeration capacity and refrigerant mass flow rate in evaporator according to the different requirement of refrigeration capacity. A finite-time thermodynamic model is developed for the refrigeration system. And the simulation results demonstrate that this capacity modulating technology is feasible. Liquid refrigerant by-pass reduces discharge temperature of compressor in the low temperature level refrigeration cycle effectively, avoids liquid slugging, and fits for HLTU to supply varying refrigeration capacity. In light of the experiment results, HLTU with liquid refrigerant by-pass can reduce refrigerating capacity and save energy when it is used at high external air temperature.