Abstract This paper conducts a numerical investigation of spacer effects on heat transfer of supercritical R-134a flows in a vertical annular channel. The simulations are conducted with SST k-ω turbulent model in Fluent 15.0. The investigation range is in the normal and improved heat transfer region at supercritical pressure. The results show that the spacer end enthalpy has remarkably influence on the spacer effects at supercritical pressure, which is different from that at subcritical pressure. In the liquid-like region, the enhancement effectiveness of spacers increases with increasing spacer end bulk enthalpy. However, in the in the gas-like region, the enhancement effectiveness of spacers decreases with increasing spacer end bulk enthalpy. The enhancement effectiveness reaches a peak value near the pseudo-critical enthalpy. For the parameters sensitivity, besides the blockage ratio, spacer end enthalpy and dimensionless distance to the spacer end, the flow parameters and local enthalpy also have significant influences on the spacer effects. Mechanism analysis shows that the characteristic of the mechanism of disruption of boundary layer is the main cause for the appearance of peak value of enhancement effectiveness near the pseudo-critical region at supercritical pressure. The HTC ratio of bare channels can be used to help the prediction of the HTC ratio in the corresponding spacer downstream.

中文翻译：

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环形通道中超临界流体传热的间隔效应数值研究

摘要 本文对垂直环形通道中超临界R-134a 流的传热效应进行了数值研究。使用 Fluent 15.0 中的 SST k-ω 湍流模型进行模拟。研究范围在超临界压力下的正常传热区和改进传热区。结果表明，间隔端焓对超临界压力下的间隔效应有显着影响，这与亚临界压力下的不同。在类液体区域，间隔物的增强效果随着间隔物末端体积焓的增加而增加。然而，在类气体区域，间隔物的增强效果随着间隔物末端体积焓的增加而降低。增强效果在伪临界焓附近达到峰值。对于参数敏感性，除了堵塞比、间隔端焓和到间隔端的无量纲距离外，流动参数和局部焓也对间隔效应有显着影响。机理分析表明，边界层破坏机制的特点是超临界压力下拟临界区附近出现增强效果峰值的主要原因。裸通道的 HTC 比率可用于帮助预测下游相应间隔区的 HTC 比率。机理分析表明，边界层破坏机制的特点是超临界压力下拟临界区附近出现增强效果峰值的主要原因。裸通道的 HTC 比率可用于帮助预测下游相应间隔区的 HTC 比率。机理分析表明，边界层破坏机制的特点是超临界压力下拟临界区附近出现增强效果峰值的主要原因。裸通道的 HTC 比率可用于帮助预测下游相应间隔区的 HTC 比率。