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Heat transfer regimes for a flow of water at supercritcal conditions in vertical channels

机译：垂直通道中超临界条件下水流的传热方式

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摘要

Heat transfer regimes observed in experiments with water at supercritical conditions flowing in vertical channels of various cross-sections (such as round pipes, annulus, or rod bundles) are analyzed. In accordance with the established practice, the normal and the deteriorated heat transfer regimes were singled out as the basic regimes specific for heat carriers with highly variable properties. At the same time, it has been established that most published experimental data on supercritical pressure water heat transfer along the length of test sections demonstrate combined (or transient) heat transfer regimes. The features can be presented as a superposition of characteristics of the above-mentioned basic regimes. The combined regimes are not stable in certain ranges of water flow conditions in which sudden transitions between the basic regimes can occur. A system of similarity criteria governing heat transfer rate in the vicinity of the critical point is examined. As applicable to cores of water-cooled reactors, due to a small hydraulic diameter of cooling channels, buoyancy forces acting in these channels are negligible as compared with the inertia effects caused by thermal acceleration of the flow and viscous force. This concept yields two integrated criteria whose use in the correction factors for the basic heat transfer equation, which we proposed previously for the normal regimes, adequately (with an error of 20-25%) describes the specific of the heat transfer coefficient in the normal, deteriorated, and combined regimes. A system of equations is proposed for design calculation of heat transfer in channels of nuclear reactors cooled with supercritical pressure water.
机译：分析了在超临界条件下水在各种横截面的垂直通道（例如圆管，环形空间或棒束）中流动的水中进行的实验中观察到的传热机制。按照既定的惯例，正常和恶化的传热机制被选为具有高度可变特性的热载体特有的基本机制。同时，已经确定的是，关于超临界压力水沿测试部分的长度方向进行热传递的大多数实验数据都证明了组合的（或瞬态的）热传递机制。这些特征可以表示为上述基本方案的特征的叠加。在某些水流条件范围内，组合的状态不稳定，在这些范围内可能发生基本状态之间的突然过渡。研究了控制临界点附近传热速率的相似性准则系统。由于冷却通道的水力直径较小，因此适用于水冷堆的堆芯，与由流动的热加速度和粘性力引起的惯性效应相比，作用在这些通道中的浮力可忽略不计。这个概念产生了两个综合标准，它们在基本传热方程的校正因子中的使用（我们先前针对正常状态提出），足以（误差为20-25％）描述了正常情况下的传热系数。 ，恶化和合并的政权。提出了一个方程组，用于设计计算超临界压力水冷却的核反应堆通道中的传热。

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