In numerical simulations on horizontal supercritical heat transfer, the tube model excluding or including the solid wall is usually employed. However, a systematic comparison and in-depth elucidation between the non-conjugate and conjugate heat transfer (NCHT, CHT) models are still in absence. To address this critical issue, the present work employs both horizontal models to perform comparative numerical simulations using the shear stress transport (SST) turbulence model. The results show that the discrepancies in heat transfer between the two modes are negligible under weak buoyancy effect. However, the inconsistencies become more pronounced with intensified buoyancy strength, especially along the top generatrix. Under strong buoyancy effect, the largest deviations in wall temperature and heat flux of the top generatrix between two modes reach up to 396.1°C and 43.5 , respectively, the incorporation of tube wall in CHT computations greatly improved the heat transfer uniformity. The mechanisms that the tube wall acts as a “damper” regulating the heat flow are revealed, which is mainly via the circumferential heat transport and spread from the top where the fluid convection thermal resistance augments; whereas the exclusion of the solid tube wall results in the loss of the surface heat flux adjustment, and the top heat transfer degradation progressively worsens then the wall temperatures sharply rise. As the buoyancy level is within the range of , the heat migration from the top within the tube wall of CHT simulations is less than 17.8%, indicating the simplified NCHT model can be effectively used for sCO heat transfer simulations of the studied horizontal tube with acceptable accuracy.

中文翻译：

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共轭热边界对超临界CO2水平管内湍流传热的影响

在水平超临界传热数值模拟中，通常采用不包括或包括实体壁的管模型。然而，非共轭传热和共轭传热（NCHT、CHT）模型之间仍缺乏系统的比较和深入的阐明。为了解决这个关键问题，目前的工作采用两种水平模型来使用剪切应力传递（SST）湍流模型进行比较数值模拟。结果表明，在弱浮力效应下，两种模式之间的传热差异可以忽略不计。然而，随着浮力强度的增强，这种不一致变得更加明显，特别是沿着顶部母线。在强浮力作用下，两种模态的壁温和顶母线热流密度最大偏差分别达到396.1℃和43.5℃，管壁纳入CHT计算大大提高了传热均匀性。揭示了管壁作为“阻尼器”调节热流的机制，主要是通过周向传热并从顶部扩散，流体对流热阻增大；而排除实心管壁会导致表面热通量调节损失，顶部传热退化逐渐恶化，壁温急剧上升。由于浮力水平在 范围内，CHT 模拟中从顶部到管壁内的热迁移小于 17.8%，表明简化的 NCHT 模型可以有效地用于所研究的水平管的 sCO 传热模拟，并且具有可接受的性能。准确性。