Internally ribbed tubes (IRTs) with better heat transfer capability have been widely applied in many fields. Several studies focused on the flow and heat transfer in IRTs with special structure configurations, but there is still lack of clear understanding regarding the influence of spiral ribs/grooves on the local flow structure and heat transfer capability of supercritical water. In the present paper, numerical simulation on turbulent heat transfer of supercritical water through a vertically upward IRTs is investigated. It is found at low heat fluxes, heat transfer enhancement occurs; the temperature of IRT is lower than that in the smooth tube by 6~7 °C, but at high heat fluxes; deteriorated heat transfer occurs in ST rather than in IRTs; the maximum temperature difference reaches 36 °C. The heat transfer ratio between IRT and ST is about 1.81 in the pseudocritical region, where the velocity deviation is about 20–50%. Once the deterioration heat transfer exists, a thin layer with high temperature but low density and low thermal conductivity so that (with a 20% reduction) fluids will be covered on the surfaces. Effects of rib height, width, lift angle and threads on turbulent heat transfer are analyzed, an optimum rib structure based on the performance evaluation criteria is obtained (α = 50°, e = 0.58 mm, S = 3.5 mm, m = 6), which can achieve the best performance.

中文翻译：

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竖向内肋肋管中超临界水传热特性的数值分析

具有更好传热能力的内肋管（IRT）已广泛应用于许多领域。一些研究集中在具有特殊结构配置的IRT中的流动和传热方面，但是对于螺旋肋/沟槽对局部流动结构和超临界水的传热能力的影响，仍然缺乏清晰的了解。本文研究了超临界水通过垂直向上的IRT湍流传热的数值模拟。发现在低热通量下，会发生传热增强。IRT的温度比光滑管的温度低6〜7°C，但在高热通量的情况下；传热恶化发生在ST而不是IRT中；最大温差达到36°C。IRT和ST之间的传热比约为1。在伪临界区中的速度为81，其中速度偏差约为20–50％。一旦存在恶化的热传递，则高温但低密度和低导热率的薄层将被覆在表面上（减少20％）。分析了肋条的高度，宽度，升角和螺纹对湍流传热的影响，根据性能评估标准获得了最佳的肋条结构（α= 50°，e = 0.58 mm，S = 3.5 mm，m = 6），可以达到最佳性能。