半球体窄缝通道流动换热与冷却能力试验

Experiment of flow and quenching for hemispherical narrow gaps

在美国TMI-2发生严重事故时,反应堆下封头内累积了大量的熔融物,经过一段时间观察,下封头未被熔融物熔穿。因此提出了一些可能的冷却机理,其中间隙冷却机理被认为是最有可能的一种。本文进行了窄通道流动换热与冷却能力的试验,旨在探索窄缝的传热机理和冷却能力。试验中半球形采用向下加热,并观察流动换热现象。在分组试验过程中窄缝间隙选取为2mm和4mm两种,采用不同的加热功率对铜球进行加热。试验结果表明:在窄通道试验中,冷却过程与壁面加热、间隙大小有着不可分割的关系;壁面温度对窄通道冷却有着较大的影响;在窄通道流动换热与冷却过程中,对于单相对流换热,强制对流冷却的效果大于自然对流的冷却效果;对于多相对流换热,强制对流的冷却效果也大于自然对流的冷却效果。

Many molten corium relocated in the lower head of TMI-2 reactor after severe accident. The lower head was not pene- trated during the accident. There are some cooling mechanisms have been suggested and a gap cooling mechanism is considered to be the most plausible one which plays a major role in the cooling of the corium. A narrow gap flow and heat transfer experiment was done to investigate mechanisms of heat transfer and the coolability. Hemispherical copper was heated downward and the flow heat transfer behavior was investigated. The gaps between the copper shell and plastic vessel were 2 mm and 4 mm, respectively. The effect of the gap cooling was investigated. In the experiment, the copper was heated with different powers, and the effects on the heat transfer should be noticed. The experimental results show that the coolability is affected by the wall heat and the gap width. The wall temperature is important for the coolability of the narrow gap. The effect of the forced convection is more markedly than that of the nature convection in single phase convection heat transfer and multi-phase convection heat transfer ex- periments.