Next step towards high-fidelity numerical simulations of turbulent heat transfer toliquid metals: forced and mixed convection with non-uniform wall heat flux, conjugate heat transfer and temperature dependent thermophysical properties

在高热流密度和中高温的应用中，液态金属（LMs）是传热流体（HTFs）的有希望的候选者。潜在的物理传热机制受到LMs高导热系数的强烈影响，与空气和水等HTFs有很大不同。尽管LMs作为高温燃料的应用显示出提高效率的潜力，但缺乏关于LMs湍流传热的高保真数据。为了提高对所涉及的物理过程的理解，本文提出了一种扩展的、彻底的数值分析。基于之前关于强迫对流的非均匀热边界条件的研究，接下来的步骤是加入浮力（混合对流）以及热交换器固体部分的热传导（共轭传热）和热物理性质的温度依赖性的影响。高保真数值模拟将由大规模并行化、高阶、开源代码Nek5000执行，该代码在之前的工作中已经过广泛的测试、验证并显示出准确的结果。两个不同普朗特数下的LM，包括例如铅铋共晶（LBE）和钠（Na），将在一系列参数范围内进行研究，这些参数范围涵盖了反对和辅助混合对流的不同制度以及不同的流体动力操作条件。本研究的结果为进一步研究影响LM传热的现象提供了信息。它们为lm中湍流传热的测试和调整以及改进模型提供了重要的参考数据。

Liquid Metals (LMs) are promising candidates for Heat Transfer Fluids (HTFs) in applications where high heat flux densities and medium to high temperatures are present. The underlying physical heat transfer mechanism is strongly influenced by the high thermal conductivity of LMs and is substantially different from HTFs like air and water.Even though the application of LMs as HTFs show the potential of increasing the efficiency there is a lack of high-fidelity data on the turbulent heat transfer of LMs. In order to improve the understanding of the involved physical processes, an extended, thorough numerical analysis is proposed herein.Based on previous work on non-uniform thermal boundary conditions for forced convection, the next steps are to add the effects of buoyancy forces (mixed convection) as well as heat conduction within the solid part of the heat exchanger (conjugate heat transfer) and the temperature dependency of thermo-physical properties.The high-fidelity numerical simulations will be performed by the massively-parallelized, high-order, open source code Nek5000, which has been extensively tested, validated and shown to yield accurate results in the previous work.LM at two different Prandtl numbers, encompassing e.g. lead-bismuth eutectic (LBE) and sodium (Na), are to be studied over a range of range of parameters covering different regimes in opposed and aided mixed convection as well as different hydrodynamic operating conditions. The results of this study provide information to which extend the investigated phenomena influence heat transfer in LM. They provide essential reference data valuable for testing and tuning as well as improving models for turbulent heat transfer in LMs.