对通道尺寸为 1400 mm ×250 mm ×2.75 mm的竖直矩形窄通道内沸腾换热特性及液滴夹带进行了实验研究,分析了不同液位、加热蒸汽流量、补液温度下换热性能以及液滴夹带的变化规律.实验结果表明:随着初始液位高度的提高会出现一个拐点,在到达拐点后,继续提高初始液位以及增加补液量将不会改变最终液位的高度;实验段的传热系数随着液位的升高先增大,并在拐点附近达到最大值,随后减小;在相对液位低时,未出现液滴夹带,而当液位逐渐接近液位拐点时,通道出口逐渐出现液体,而夹带量在液位达到拐点后迅速上升;随着加热蒸汽流量的提高,换热量的增加使沸腾换热更加剧烈,传热系数和带液量显著增大;补液温度越高,传热系数越大,但是补液温度对带液量无明显影响.
Experimental Study on Boiling Heat Transfer Characteristics and Droplet Entraiment in a Vertical Rectangular Narrow Channel
The experimental study was carried out on the boiling heat transfer characteristics and droplet entrainment in a vertical rectangular narrow channel with the size of 1 400 mm x 250 mm × 2.75 mm.The variation law of heat transfer performance and droplet entrainment was analyzed under different liquid levels,heating steam flow rates and replenishment temperatures.The experimental results indicate that there is a point of inflection as the initial liquid level height increases.After reaching the inflection point,continuing to increase the initial liquid level and increasing the amount of replenishment can not change the height of the final liquid level;the heat transfer coefficient of the test section first increases with the increase of liquid level,reaches its maximum value near the inflection point,and then decreases;when the relative liquid level is low,there is no droplet entrainment.However,as the liquid level gradually approaches the inflection point,droplet gradually appears at the outlet of the channel,and the amount of entrainment rapidly increases after the liquid level reaches the inflection point;with the increase of heat-ing steam flow rate,boiling heat transfer becomes more intense and the heat transfer coefficient and the a-mount of droplet entrainment significantly increase;the higher the replenishment temperature is,the greater the heat transfer coefficient is,but the replenishment temperature has no significant effect on the amount of droplet entrainment.
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