结霜工况下重力供液与直接膨胀供液制冷系统运行特性

摘要

以R404A为工质,用热平衡法测试结霜工况下直接膨胀供液制冷系统以及重力供液制冷系统在不同蒸发器供液高度时的系统的运行特性,并进行比较.研究表明:在重力供液制冷系统中,蒸发温度和压力高于直接膨胀供液制冷系统,且受供液高度和环境温度影响;在不同供液高度时,重力供液制冷系统压缩机吸气压力高于直接膨胀供液制冷系统压缩机吸气压力,供液高度的增加,吸气压力升高,压缩机的排气压力的变化趋势与蒸发压力相似;重力供液制冷系统制冷量高于直接膨胀供液制冷系统制冷量,且随蒸发温度升高而增大,但制冷量的增加幅度却有着相反的变化趋势.供液高度为1200mm时,制冷量最大增幅达到35.59%;重力供液制冷系统COP大于直接膨胀供液制冷系统COP,重力供液制冷系统存在最佳供液高度.%Using thermal balance method and R404A as refrigerant, the operating characteristics of refrigeration system with supply liquid refrigerant by gravity (RSSLRG) and direct expansion have been analyzed by experimental method in frost formation operating mode. The experiments indicate that the evaporating temperature and pressure of RSSLRG are higher than that of direct expansion system and affected by evaporating temperature and supplying height. In different supplying height of RSSLRG, the suction pressure and discharge pressure are higher than that of direct expansion system and changed with supplying height and environment temperature. The refrigerating capacity of RSSLRG is larger than that of direct expansion system and increasing with evaporating temperature, but the additional magnitude has opposite change trends. When supplying height is h1=1200mm, the max additional magnitude is 35.59%. In addition, the COP of RSSLRG is higher than that of direct expansion system, and it remarks that the RSSLRG exits an optimal supplying height.