基于滴膜共存理论热虹吸管冷凝段传热模型

引入滴膜共存冷凝传热理论分析管内存在滴状冷凝的热虹吸管冷凝段传热,将热虹吸管冷凝段传热表示为滴状区和膜状区传热之和建立传热模型。滴状区,以Rose冷凝传热模型计算单个液滴的传热,基于随机分形理论建立了液滴的空间和尺度分布函数,进而求解整个滴状区的热通量。膜状区,根据Nusselt竖壁层流膜状凝结理论进行热通量的计算。通过沟流级别计算滴状区和膜状区的面积比率,从而建立滴膜共存冷凝传热模型。传热模型计算结果与实验结果较为吻合,能够反应热管冷凝段传热本质。

Heat transfer model of thermosyphon condenser based on dropwise and film co-existing condensation theory

The theory of dropwise and film co-existing condensation was introduced to elucidate the heat transfer characteristics in the condensing section of a two-phase closed thermosyphon.The heat flux in the condensing section was expressed as the sum of the heat flux through the dropwise region and rivulet filmwise region.The heat transfer model in the dropwise region was proposed,based on the fractal characteristics associated with spatial and size distributions of drops on the condensing surface.The heat flux through a single drop was calculated by using Rose classical model.In the rivulet filmwise region,the liquid film thickness and the area fraction covered by the rivulet region were calculated by using Nusselt model of condensation through a liquid film on a vertical wall.The ratio of area covered by drops to that covered by film was obtained by the rivulet degree.The heat flux prediction based on the proposed model agrees well with the experimental results,and thus it can reflect the substantial heat transfer mechanism of the condensing section of the thermosyphon.