In the struggle for a more sustainable economy, thermal energy storage is a relevant solution either for solving the intermittency that is intrinsic to many renewable power plants, or for promoting energy efficiency and the reuse of waste heat. Among the available storage technologies, some rely on latent heat with solid-liquid phase transitions, where natural convection often plays a significant role. For practical and historical reasons, this problem is usually modeled through diffuse interface methods involving two fundamental effects that require specific treatment. The first one concerns canceling the velocity field in the solid phase, usually handled with a penalization term. The second one deals with the phase change property, and is roughly connected to the melting temperature or temperature range of the phase change (pure substances and mixtures respectively) and associated latent heats. Two main issues are associated with these parameters: firstly, there is no reliable method to unambiguously determine them, and secondly and more importantly, their influence and mutual interaction have received little attention. The present study aims to tackle these issues and to help non-specialists or engineers to have a clearer view of the possible mistakes or confusions that can easily pollute such simulations. As a rule of thumb, it is thus demonstrated that the proper definition of the temperature range for the phase change is a cornerstone, equally significant with the latent heat. Moreover, the penalization term (i.e. the mushy zone constant) can compete with or hide the effects of this transition range. This means that its value is not independent of the temperature range in which the phase transition occurs. Consequently, its value should be set carefully.

中文翻译：

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对流主导熔融模拟的一些关键因素的数值研究


在争取更可持续的经济的过程中，热能存储是一种相关的解决方案，可以解决许多可再生发电厂固有的间歇性问题，也可以提高能源效率和废热的再利用。在可用的存储技术中，有些依赖于固液相变的潜热，其中自然对流通常发挥重要作用。出于实际和历史原因，该问题通常通过扩散界面方法进行建模，涉及需要特定处理的两个基本效应。第一个涉及消除固相中的速度场，通常用惩罚项处理。第二个涉及相变性质，大致与相变的熔化温度或温度范围（分别为纯物质和混合物）以及相关的潜热有关。与这些参数相关的两个主要问题：首先，没有可靠的方法来明确确定它们，其次也是更重要的是，它们的影响和相互影响很少受到关注。本研究旨在解决这些问题，并帮助非专业人士或工程师更清楚地了解可能容易污染此类模拟的错误或混乱。根据经验，这证明相变温度范围的正确定义是一个基石，与潜热同样重要。此外，惩罚项（即糊状区域常数）可以与该过渡范围竞争或隐藏该过渡范围的影响。这意味着它的值并不独立于发生相变的温度范围。因此，应仔细设置其值。