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本文通过实验研究了池沸腾和液膜沸腾条件下的临界热流密度。实验结果表明,初始液膜厚度对于临界热流密度没有影响,并且液膜沸腾的临界热流密度值和相同条件下的池沸腾的临界热流密度值相当。这一实验结果验证了‘尺度分离’假设。通过高速摄像机对液膜沸腾进行直接观测,发现在高热流密度时,绝大多数的气泡底下有微液膜存在,只有少量气泡底下出现干斑,但是由于高频的气泡生长过程,干斑很快被润湿而消失。接近临界热流密度时,干斑的面积占据整个加热表面的比例不超过10%。当热流密度达到临界值时,干斑由于不能被润湿而渐渐扩大,最后导致加热壁面烧毁。
In this paper, we study the critical heat flux density under the conditions of pool boiling and liquid film boiling experimentally. The experimental results show that the initial liquid film thickness has no effect on the critical heat flux density, and the critical heat flux density value of liquid film boiling is equal to the critical heat flux value of pool boiling under the same conditions. This experimental result validates the ’scale separation’ hypothesis. Direct observation of liquid film boiling by high-speed camera showed that at the high heat flux density, most of the bubbles exist under the micro-liquid film, and only a few bubbles appear dry spots, but due to the high-frequency bubble growth process, dry spots are very Quickly be wet and disappear. Near critical heat flux density, the area of dry spots occupies no more than 10% of the total heating surface. When the heat flux density reaches the critical value, the dry spots gradually expand due to the inability to be wetted, which eventually leads to the burning of the heated wall.