In power plants, the condenser section plays an important role in total thermal efficiency. Extensive considerations by researchers are put toward increasing the heat dissipation efficiency while maintaining low cost and water consumption. One way to archive such situation is to consider replacing the water cooled condenser (WCC) with an air cooled condenser (ACC), but resulting in a significant increase in the condenser size due to the relatively low heat transfer coefficient (HTC = 20 -50 W/m~2K) of the air compared to that of the water. Inspired by the phase change heat transfer of water during the perspiration of mammals, a sweating boosted air cooling approach is proposed herein to dramatically increasing the HTC and minimizing the water consumption. In this experimental study, a wind tunnel and distilled water dripping system were used to examine the thermal performance of copper samples with a tested surface area of 2 in by 2 in. Two surface enhancement approaches were adapted herein. In the first approach, the testing samples were integrated with microchannels, copper woven meshes (200 meshes/in) that were sintered on top of the surface, and finally nanostructures that was synthesized by a hot alkaline oxidation process. In the second approach, the tested samples were coated with TiO2 via an atomic layer deposition (ALD) process. This method allows for rapidly spreading of the dripping water droplets over the whole tested surface. This rapid spreading behavior is due to two main reasons, first the low resistance flow of microchannel which delivered the water globally; second the high capillary pressure generated by the micro-ano- structures which delivered the water locally. Three different flat-surface samples were developed in this study, as flat surface with sintered copper meshes (design A), grooved surface with sintered copper meshes (design B); and grooved surface with sintered copper meshes coated with ALD TiO2 film (design C). The performance of the surfaces of this approach was quantitatively characterized with the wick testing. The heat transfer performances for all samples were also examined. The experimental results showed that the convection heat transfer plays a limited role in the heat dissipation. In addition, HTC was enhanced by increasing the dripping water rate consumption until the surface reached the flooding condition. The results showed that the evaporation rate of water was augmented with the increase of Reynolds number. The maximum HTC was 182.45 W/m~2K with a water dripping rate of 12 ml/h, resulting in an enhancement approximately 214.07% compared to the case without water dripping. Further research on a higher HTC requires an optimized combination of Reynolds number and water consumption.
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机译：在发电厂中，冷凝器部分对总热效率起着重要作用。研究人员对提高散热效率同时保持低成本和水消耗进行了广泛的考虑。解决这种情况的一种方法是考虑用风冷冷凝器（ACC）替换水冷冷凝器（WCC），但由于传热系数相对较低（HTC = 20 -50 W / m〜2K）与水相比。受哺乳动物出汗期间水的相变传热的启发，本文提出了出汗促进空气冷却的方法，以显着增加HTC并使水消耗最小化。在该实验研究中，使用风洞和蒸馏水滴落系统检查了测试表面积为2 in x 2 in的铜样品的热性能。本文采用了两种表面增强方法。在第一种方法中，将测试样品与微通道，在表面顶部烧结的铜编织网（200目/英寸）集成在一起，最后与通过热碱性氧化工艺合成的纳米结构集成在一起。在第二种方法中，通过原子层沉积（ALD）工艺将测试样品涂上TiO2。这种方法可以使滴落的水滴迅速散布在整个测试表面上。这种迅速的传播行为是由于两个主要原因，首先是微通道的低阻力流，该微通道向全球输送了水。其次，由微/纳米结构产生的高毛细管压力将水局部输送。在这项研究中开发了三种不同的平面样品，分别是带有烧结铜网的平坦表面（设计A），带有烧结铜网的沟槽表面（设计B）;槽表面带有ALD TiO2薄膜涂层的烧结铜网（设计C）。该方法的表面性能通过吸液芯测试进行了定量表征。还检查了所有样品的传热性能。实验结果表明，对流换热在散热中的作用有限。另外，通过增加滴水率的消耗直至地表达到淹没状态，从而提高了HTC。结果表明，水的蒸发速率随雷诺数的增加而增加。 HTC的最大值为182.45 W / m〜2K，滴水率为12 ml / h，与不滴水的情况相比，提高了约214.07％。对更高的HTC的进一步研究需要雷诺数和水消耗的优化组合。
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