Heat Transfer Characteristics and transition Mode in condensation Curves

采用特制的凝结液流向长度较大的冷凝块，对冷凝面上游冷凝水流动的影响进行了实验研究。换热块由六个热独立的铜子块组成，用于测量局部换热值，并消除了换热面边缘的影响。冷凝表面吸附的丙二醇和乙二醇两种有机蒸气和十八硫醇分别作为试验蒸汽和实现疏水表面的促进剂。给出了局部热流密度和换热系数的分布、凝结程度以及上游冷凝水覆盖的表面分数。在此基础上，利用由分离液滴直径归一化的无量纲距离，系统地确定了过渡区冷凝深度小河的数密度，以及最大热流点处的最大热流密度和最大热流点处的冷凝水所覆盖的表面积对冷凝水流动方向的依赖关系。

An experiment was carried out on the effect of condensate flow from upstream of the condensing surface by using a specially devised condensing block which had relatively large length in the direction of condensate flow. The heat transfer block was composed of thermally independent six copper sub-blocks to measure the local values of heat transfer, and was built to remove the effect of the edge of heat transfer surface. Two kinds of organic vapors, i. e. propylene glycol and ethylene glycol vapors, and octadecanethiol adsorbed on the condensing surface were used as a test vapor and a promoter realizing the lyophobic surface, respectively. The results of the distributions of local heat flux and heat transfer coefficient, the aspect of condensation and the surface fractions covered by condensate flowing from upstream were shown. Further, it was clarified that the number density of the rivulets of depdrting condensate formed in the transition region and the dependencies of maximum heat flux and the surface fraction covered bydeparting condensate at the maximum heat flux point on the direction of condensate flow were determined systematically by using non-dimensional distance normalized by the departing drop diameter.