对流效应下幂律流体接触熔化理论及实验研究  

Theoretical and Experimental Study of Close-contact Melting for Power-law Fluids Under Convective Effects

作　　者：胡楠[1] 许哲文 李梓瑞 范利武[1,2] HU Nan;XU Zhewen;LI Zirui;FAN Liwu(Institute of Thermal Science and Power Systems,School of Energy Engineering,Zhejiang University,Hangzhou 310027,China;State Key Laboratory of Clean Energy Utilization,Zhejiang University,Hangzhou 310027,China)

机构地区：[1]浙江大学能源工程学院热工与动力系统研究所,杭州310027 [2]浙江大学能源清洁利用国家重点实验室,杭州310027

出　　处：《工程热物理学报》2023年第1期162-170,共9页Journal of Engineering Thermophysics

基　　金：国家自然科学基金面上项目(No.52276088)。

摘　　要：接触熔化是一种具有高传热速率的固液相变形式,但现有研究通常假设相变材料为牛顿流体,也未考虑熔融薄液膜内的对流效应。本文基于幂律流变模型和标度分析建立了对流效应下典型非牛顿流体接触熔化的理论模型,利用基于拍照记录法和激光干涉法分别测量了瞬时熔化率和薄液膜厚度。结果表明,模型能准确地预测幂律流体接触熔化过程中的熔化速率和液膜厚度变化规律,液膜中的对流效应会降低固液相界面上的热通量从而导致熔化速率降低。液膜内对流受斯蒂芬数Ste、幂律系数C和幂律指数n影响,而基本与相变材料的样品高宽比和固液密度比无关。减小幂律系数C和幂律指数n会加速熔化过程,熔化末期的液膜厚度取决于幂律系数C。Close-contact melting(CCM) is a form of solid-liquid phase change with high heat transfer rate, but the existing studies usually assume that the phase change materials(PCM) are Newtonian fluids and that the convective effects within the molten thin liquid film are neglected.In this paper, a theoretical CCM model for typical non-Newtonian fluids under convective effects is developed based on the power-law rheological model and the scaling analysis. The instantaneous melting rate and the thickness of the thin liquid film are measured using the photo-based recording method and the laser interference method, respectively. The results show that the model can accurately predict the melting rate and liquid film thickness during the CCM of power-law fluid, and the convective effect in the liquid film will reduce the heat flux at the solid-liquid phase interface, leading to a slower melting rate. The convection in the liquid film is influenced by the Stephan number,power-law coefficient C and exponent n, which are independent of the aspect ratio and solid-liquid density ratio of the PCM. Decreasing the power-law coefficient C and exponent n accelerates the melting process, and the thickness of the liquid film at the end of melting depends on the power-law coefficient C.

关 键 词：相变材料 接触熔化 薄液膜 幂律流体 对流效应 

分 类 号：TK121[动力工程及工程热物理—工程热物理]