V形沟槽纳米线团簇表面的毛细抽吸-补液蒸发传热特性研究

Heat transfer characteristics of capillary pumping-replenishment evaporation on nanowire clusters surfaces with V-grooves

利用V形沟槽纳米线团簇表面的毛细抽吸和补液特征,结合实验观测和建模分析对表面的薄液膜蒸发进行研究。探究了表面结构参数和沟槽液位对蒸发性能的影响,建立薄液膜蒸发模型求解纳米线团簇和V形沟槽中的液膜轮廓方程并分析传热性能。结果表明,随着纳米线直径减小和高度增大,薄液膜蒸发传热系数增大,最高可达369kW/(m_(2)·K)。团簇内液膜在毛细力驱动下具有极高的爬升速度,使得小持液量下液膜仍位于团簇顶端蒸发。沟槽液膜完全润湿沟槽且与团簇顶端液膜相连通,为团簇蒸发补液,沟槽液位下降不影响团簇顶端蒸发,能够延伸薄液膜长度并减薄沟槽侧壁液膜厚度,进一步强化传热。纳米线团簇中液膜宏观传热系数显著高于沟槽,证明了团簇在整体蒸发中的决定性贡献,阐明了V形沟槽纳米线团簇表面薄液膜蒸发微观机制。

Capillary pumping and replenishment features on nanowire clusters surfaces with V-grooves were used to investigate thin liquid film evaporation on nanowire clusters surfaces with V-grooves by experimental observation and model analysis.The effects of surface structural parameters and the liquid level of grooves on the evaporation performance were investigated,and a thin liquid film evaporation model was established to solve the equations of liquid film profiles in nanowire clusters and V-grooves,and to analyze the heat transfer performance.The results show that the heat transfer coefficient of thin liquid film evaporation increases with the decrease of nanowire diameter and the increase of nanowire height,up to 369 kW/(m^(2)·K).The liquid film in the cluster has an extremely high climbing speed driven by capillary force,so that the liquid film still evaporates at the top of the cluster under small liquid holding volume.The liquid film in V-grooves completely wets the trench and connects with the liquid film at the top of the clusters to replenish the liquid for the evaporation of the clusters,and the drop of the liquid level in grooves does not affect the evaporation in the top of clusters,which extends the length of the thin liquid film and decreases the thickness of the liquid film on the side wall of the groove to further strengthen the heat transfer.The macroscopic heat transfer coefficient of the liquid film in the nanowire clusters is significantly higher than that in the grooves,which proves the decisive role of the clusters in the overall evaporation,and elucidates the microscopic mechanism of the thin liquid film evaporation on nanowire clusters surfaces with V-grooves.