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首页> 外文期刊>International communications in heat and mass transfer >An empirical study on evaporation heat transfer characteristics and flow pattern visualization in tubes with coiled wire inserts
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An empirical study on evaporation heat transfer characteristics and flow pattern visualization in tubes with coiled wire inserts

机译：盘绕金属丝管中蒸发传热特性和流型可视化的实证研究

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In the present work, heat transfer and flow pattern visualization during forced convection evaporation of hydrocarbon R-600a (Isobutane) inside a horizontal tube with coiled wire inserts has been experimentally studied. The system consists of a pump, two preheaters, the test section, two condensers, flow meter and bypass. The test evaporator was an electrically heated copper tube of 1000 mm length, 8.1 mm inside diameter and a wall thickness of 0.71 mm. Coiled wires with three different wire diameters of 0.5,1.0 and 1.5 mm and three different coil pitches of 10,20 and 30 mm were made and used in full length of test evaporator. The test runs were carried out at refrigerant mass fluxes from 109.2 to 505 kg/m~2 s and heat fluxes between 18.6 and 26.1 kW/m~2. The use of coiled wires was found to increase the flow boiling heat transfer coefficients up to maximum value of 124% above the plain tube values with wire coiled having a twist ratio (~p/_(D_(in)) ) of 1.243 and a thickness ratio {~e/_(D_(in)) of 0.183. Four different flow patterns were observed and classified as bubbly, stratified, intermittent and annular flow. This study reveals the developments of the flow patterns. Also it was observed that the presence of coiled wire inserts induces disturbance into gas and liquid flows and so that the shape and motion of bubbles and slug are different from those observed in a plain tube. The correlation suggested by Shah gave the best prediction to the flow boiling heat transfer coefficient in the plain tube within the studied ranges.
机译：在目前的工作中，已经对通过缠绕金属丝插入的水平管内的碳氢化合物R-600a（异丁烷）的强制对流蒸发过程中的传热和流态可视化进行了实验研究。该系统由一个泵，两个预热器，测试部分，两个冷凝器，流量计和旁路组成。测试蒸发器是长度为1000毫米，内径为8.1毫米，壁厚为0.71毫米的电加热铜管。制作了三种直径分别为0.5、1.0和1.5 mm的线圈导线以及三种不同的螺距为10,20和30 mm的线圈导线，并将其用于测试蒸发器的全长。在制冷剂质量通量为109.2至505 kg / m〜2 s和热通量为18.6至26.1 kW / m〜2的条件下进行测试。发现使用盘绕的线绕线时，其沸腾传热系数可增加至比普通管值高124％的最大值，盘绕的盘绕线的扭曲比（〜p / _（D_（in）））为1.243。厚度比{〜e / _（D_（in））为0.183。观察到四种不同的流型，并分为气泡流，分层流，间歇流和环形流。这项研究揭示了流动模式的发展。还观察到，盘绕的金属丝插入物的存在引起了对气体和液体流动的干扰，因此气泡和弹丸的形状和运动与在普通管中观察到的不同。 Shah提出的相关性对研究范围内的普通管中的流动沸腾传热系数给出了最佳预测。

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