直接供液与重力供液制冷系统的对比研究

重力再循环供液是指蒸发器依靠制冷剂自身的重力送入蒸发器,在供液高度大于蒸发器对制冷剂的阻力情况下,部分制冷剂液体在蒸发器和气液分离器所形成的回路中再循环。由于再循环作用不需要外加动力,并强化管内制冷剂的沸腾换热,蒸发器的效率得以明显提高。文中介绍了重力再循环供液制冷系统和蒸发器的结构,提出采用J.Chawla关系式和Shah关联式相结合的方法预测再循环蒸发器制冷剂侧的换热系数。采用空气侧热平衡法,对直接膨胀供液和重力再循环供液制冷系统分别进行了多蒸发温度下的性能测试。表明重力再循环供液制冷系统比直接膨胀供液制冷系统的制冷量平均增加26%,COP平均增加18%,蒸发温度平均升高1.1℃,传热系数是直接供液的1.57倍。J.Chawla关系式和Shah关联式相结合预测再循环蒸发器制冷剂侧的换热系数,其曲线结构与实验值近似,平均误差不大于20.6%。文章还对各热工参数的变化原因进行了分析。

Comparative study on the supply liquid of direct expansion cooling system and gravity recirculation cooling system

Gravity recycling for liquid means that the refrigerant flows into evaporator by its own gravity if the liquid height is greater than the resistance of evaporator.And part of the refrigerant liquid which is formation by evaporator and gas-liquid separator will recycle in the loop.Due to the recycling system doesn’t require additional power,but enhancing the boiling heat transfer of the refrigerant in the tube,so the efficiency of evaporator can be significantly improved.This article described the recycling of gravity for liquid cooling system and the structure of the evaporator first,then put forward with the method of combining J.Chawla relation and Shah relation.In this way,we could predict the heat transfer coefficient of the recycling evaporator refrigerant.Using the method of Air-side heat balance,performance test of more evaporation temperature was carried out with the supply liquid of direct expansion and gravity recirculation cooling system.Compared with the direct expansion cooling system,the cooling capacity of the gravity recirculation cooling system is increased by an average of 26%,COP increased by an average of 18%,heat transfer coefficient is 1.57 times of the direct expansion cooling system.Combined of the relation J.Chawla and the relation Shah,predict the heat transfer coefficient of the recirculation evaporator refrigerant was predicted and the curve structure was similar to the experimental value,and the average error is less than 20.6%.This article also made an analysis about the cause of the thermal parameters’ change.