梯形沟槽-丝网复合吸液芯圆柱热管传热特性的数值研究

Numerical Study of Heat Transfer Characteristics in Cylindrical Heat Pipes with Trapezoidal Groove-Mesh Composite Wick

摘要

本文通过建立圆柱热管内部相间耦合的二维瞬态数值模型，对水平放置条件下梯形沟槽-丝网复合吸液芯热管的流动与传热特性进行研究。采用多孔介质模型并结合用户自定义函数(UDF)，模拟了复合吸液芯中气液流动与传热过程。研究结果表明，相比单一的梯形沟槽吸液芯，复合吸液芯因过流面积的变化改变了工质流动状态，液相流速与压降随吸液芯流道增宽而减小，气相流速与压降则因蒸汽腔流道收缩而增大。高目数丝网虽因高导热性降低了热阻，但也因低渗透率加剧了流动损失，从而削弱了工质回流能力。此外，蒸发段热流密度的增大在强化传热的同时，也会形成显著的气液两相压降梯度，进一步削弱了回流驱动力。

Abstract

A two-dimensional transient numerical model with interphase coupling inside a cylindrical heat pipe is established to investigate the flow and heat transfer characteristics of a horizontal trapezoidal groove-mesh composite wick heat pipe. A porous medium model combined with a user-defined function (UDF) is adopted to simulate the gas-liquid flow and heat transfer processes within the composite wick. The results show that compared with the single trapezoidal groove wick, the composite wick changes the flow pattern of the working fluid due to the variation of the flow cross-sectional area. The liquid velocity and pressure drop decrease with the widening of the wick channel, while the vapor velocity and pressure drop increase as a result of the contraction of the vapor chamber channel. Although a high-density mesh screen helps reduce thermal resistance owing to its high thermal conductivity, its low permeability aggravates the flow loss and thus weakens the backflow capacity of the working fluid. In addition, increasing the heat flux in the evaporator section enhances heat transfer, but also induces a significant gas-liquid pressure drop gradient, which further limits the backflow driving force.

关键词

热管 / 复合吸液芯 / 瞬态模型 / 流动特性 / 传热特性

Key words

heat pipe / composite wick / transient model / flow characteristics / heat transfer characteristics

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