风速对不同流程数CO2蒸发器性能的影响

为研究迎面风速对不同流路数CO₂翅片管蒸发器性能的影响,本文建立分布参数模型对蒸发温度为-25℃,风速为0.5～4 m/s条件下5种流路数CO₂翅片管蒸发器的制冷剂压降、换热量、温度分布及传热系数的变化进行分析,并通过实验验证了蒸发器模型的可靠性。蒸发器模型的换热量、制冷剂压降和风侧压降等参数模拟值与相同工况下实验值的误差均在±4%以内。结果表明:同一流路数蒸发器的换热量、制冷剂压降及传热系数均随风速的增大而增大,而其涨幅随风速增大而减小,综合考虑换热效果和能耗可得最佳风速范围为2.5～3.5 m/s;在一定风速条件下,蒸发器设计时在合理范围内选择较多流路数可有效提升蒸发器换热性能并增强换热均匀性,本次实验中24流路蒸发器为最佳设计方案。

Effect of Air Velocity on the Performance of CO2 Evaporator with Different Flow Numbers

In order to study the relationship between air velocity and heat transfer performance of CO₂ finned-tube evaporator,a distributed parameter model was established in this paper.The changes of refrigerant pressure drop,heat transfer,temperature distribution and heat transfer coefficient of five kinds of flow-number were analyzed under conditions of evaporation temperature of-25℃and air velocity of 0.5~4 m/s,and the reliability of the model was experimentally verified.Compared with the experimental values under the same working conditions,the relative error of the simulation model for predicting the heat transfer,refrigerant pressure drop and air side pressure drop was less than±4%.Simulations demonstrated the heat transfer,refrigerant pressure drop and heat transfer coefficient of the evaporator with the same flow number all increase with the increase of air velocity,while the increase range decreases with the increase of wind speed.The optimal air velocity range is 2.5~3.5 m/s,reflecting the heat transfer effect and energy consumption.Choosing more flow numbers in a reasonable range can effectively improve the heat transfer performance and enhance the heat transfer uniformity in evaporator design.In this experiment,the 24 flow number evaporator is the best design scheme.