自然工质R290与R22滴状凝结换热特性的对比分析

通过对自然工质R290与传统工质R22滴状凝结换热特性的对比分析得出,表面过冷度要远大于蒸气饱和温度对直接凝结长大小液滴的最小半径和临界半径的影响,过冷度越大,小液滴半径和临界半径越小,R290的小液滴半径和临界半径与R22的相比相差不大。通过R290与R22制冷工质单个液滴的传热量随着接触角的增加呈现出先增加后减小的变化趋势,存在最大值。通过单个液滴的传热量随着表面过冷度的增加而增大,随着饱和温度的升高而减小,通过R290单个液滴的传热量要明显大于通过R22单个液滴的传热量。通过R290与R22滴状凝结换热表面的热通量随接触角的变化具有最大值,存在最佳的接触角。R290滴状凝结换热的热通量要明显大于R22滴状凝结换热的热通量。

Analysis on heat transfer characteristic of dropwise condensation of natural refrigerant R290 and R22

By comparing the heat transfer characteristics of dropwise condensation of natural refrigerant R290 and conventional refrigerant R22,following conclusions are obtained.The effect of surface subcooling degree on the smallest radius and the critical radius of droplet is much larger than that of the saturation temperature,and larger surface subcooling degree makes the smallest radius and the critical radius of droplet smaller.The smallest radius and the critical radius of R290 show little difference from those of R22.The heat transfer capacity through the single droplet of R290 or R22 increases first and then decreases with the increase of contact angle,suggesting the existence of the maximum heat transfer capacity.The heat transfer capacity through the single droplet increases with the increase of surface subcooling degree and decreases with the increase of the saturation temperature.The heat transfer capacity through the single droplet of R290 is obviously larger than that of R22.The dropwise condensation heat flux of R290 or R22 through the heat transfer surface has maximum value at the optimum contact angle.The dropwise condensation heat flux of R290 is obviously higher than that of R22.