Abstract This paper utilizes the CFD approaches to investigate the unsteady flow, heat and mass transfer mechanisms in an axial microchannel Ω-shape aluminum-ammonia grooved heat pipe (GHP) under zero gravity condition. The established numerical model considers the spurious velocity due to discretizing the gradient term of phase volume fraction adjacent to the phase interface. The dynamic contact angle, which is a function of the local velocity, is also modeled based on the Hoffman function via user-defined function (UDF). The Lee model is used to calculate the mass transfer rate between the phases in the evaporator as well as condenser section, while the empirical coefficients in the model are calibrated by comparing the calculated temperature distributions with the experimental data by ourselves. The whole mathematical framework is also evaluated by the experiment. Different heat flux and filling ratios are modeled to probe the heat transfer mechanisms in the GHP. The results capture the pressure profiles along the axial direction and the pressure difference across the phase interface in the cross-section perpendicular to the axis, which is balanced by the surface tension with the different contact angles along the axis. It is found that the Ω-shape GHP is capable of transporting heat over relatively large distances with a minuscule temperature difference. The results give rich insights into the flow, heat and mass transfer mechanism of the studied heat pipe.

中文翻译：

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零重力条件下微通道Ω形热管流动传热机理的CFD分析

摘要 本文利用CFD方法研究了零重力条件下轴向微通道Ω形铝氨槽热管(GHP)中的非定常流动、传热和传质机制。建立的数值模型考虑了由于离散相界面附近相体积分数的梯度项而引起的寄生速度。动态接触角是局部速度的函数，也是基于霍夫曼函数通过用户定义函数 (UDF) 建模的。Lee 模型用于计算蒸发器和冷凝器段中各相之间的传质速率，而模型中的经验系数是通过将计算出的温度分布与我们自己的实验数据进行比较来校准的。整个数学框架也通过实验进行评估。对不同的热通量和填充率进行建模以探测 GHP 中的传热机制。结果捕获了沿轴向的压力分布和垂直于轴的横截面中相界面上的压力差，这通过沿轴具有不同接触角的表面张力来平衡。发现Ω形GHP能够以微小的温差在相对较大的距离上传输热量。结果对所研究的热管的流动、传热和传质机制提供了丰富的见解。结果捕获了沿轴向的压力分布和垂直于轴的横截面中相界面上的压力差，这通过沿轴具有不同接触角的表面张力来平衡。发现Ω形GHP能够以微小的温差在相对较大的距离上传输热量。结果对所研究的热管的流动、传热和传质机制提供了丰富的见解。结果捕获了沿轴向的压力分布和垂直于轴的横截面中相界面上的压力差，这通过沿轴具有不同接触角的表面张力来平衡。发现Ω形GHP能够以微小的温差在相对较大的距离上传输热量。结果对所研究的热管的流动、传热和传质机制提供了丰富的见解。