再循环重力供液制冷系统实验

Experiment on refrigeration system with supply liquid refrigerant for evaporator by gravity

对重力供液制冷系统形成再循环的条件和再循环时蒸发器的传热性能进行理论分析,建立相应的数学模型。将重力供液制冷系统与直接膨胀供液制冷系统进行比较,得到两种不同制冷系统工作特性上的差异。通过在焓差实验室中测定制冷系统在不同工况下的压力、风量、制冷量以及耗功等技术参数,得到重力供液制冷系统和直接膨胀供液制冷系统在室外干球温度一定的情况下传热系数、制冷量以及系统COP的变化规律。实验表明:再循环的形成可以增大制冷剂流速同时充分润湿传热表面,强化换热效果显著,在测试的工况下蒸发器的传热系数可增大近40%,COP最大提高7.6%,低温工况的增幅更大。

The conditions of re-circulation in the refrigeration system with supply liquid refrigerant and heat transmission performance of evaporator in re-circulation were analyzed and the corresponding mathematical model was established. By comparing the supply liquid refrigerant by gravity with direct expansion supply liquid refrigerant, the difference of operating characteristic between two different kinds of refrigeration systems was obtained. Through determining the parameters of temperature, pressure, air volume and waste work under different operating mode in the enthalpy difference laboratory, the changing rules of evaporating temperature, refrigerating capacity and COP of the systems in certain outdoor dry bulb temperatures of sup- ply liquid refrigerant for by gravity and direct expansion were obtained. The experiment indicated that through re-circulation, increasing velocity of refrigerant can strengthen the heat transmission and the heat transfer coefficient of evaporator increased. Under the low temperature -operating mode, the system thermalsiphon phenomenon was more obvious and the refrigeration system with supply liquid refrigerant for evaporator by gravity has much better heat-transfer characteristics than the direct expansion refrigeration system.The heat transfer coefficient increase nearly 40% and COP increase 7.6%.