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首页> 外文期刊>International Journal of Heat and Mass Transfer >Thermal-hydraulic performance and entropy generation of supercritical carbon dioxide in heat exchanger channels with teardrop dimple/protrusion
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Thermal-hydraulic performance and entropy generation of supercritical carbon dioxide in heat exchanger channels with teardrop dimple/protrusion

机译：带有泪滴凹痕/凸起的换热器通道中超临界二氧化碳的热工水力性能和熵产生

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摘要

Supercritical carbon dioxide (SCO2) is an excellent candidate for refrigeration system, energy utilization and new power cycle due to its easy-to-reach pseudo-critical point and the advantages of thermophysical properties. As an efficient and passive thermal control technology, teardrop dimple/protrusion has great potential in heat transfer enhancement and resistance reduction. In this paper, three types of teardrop dimple and protrusions are novelly introduced into the SCO2 rectangular channels. Numerical calculations have been carried out to obtain the detailed flow structures, friction and heat transfer characteristics, overall thermal performance and amount of entropy generation under full turbulence regions. Moreover, the effects of geometrical structure, eccentricity of teardrop dimple/protrusion, Re, temperature and pressure of SCO2 are discussed with in-depth analysis. According to the results, complex and different evolution and development patterns of vortices are presented for three different structures. Positive eccentricity dimple (PED) produces the best overall thermal performance, owing to significant heat transfer enhancement and less friction, and the maximum TP reaches 1.17, indicating a 17% improvement compared with the smooth case. The variation of eccentricity has little effect on overall thermal performance and entropy generation for PED structure, while plays a major role in positive eccentricity protrusion (PEP) and negative eccentricity protrusion (NEP) cases. However, the increase of Re is unfavorable to the overall thermal performance. In addition, the temperature and pressure of CO2 have significant effects on the overall thermal performance for PED cases, and corresponding high TP and thermal performance deterioration regions have been captured, which is advantageous to fast positioning the specific ranges of temperature and pressure, and whose coupled mode. Specifically, the maximum TP greater than 6 can be obtained near the temperature 305 K and pressure 8 MPa. (C) 2019 Elsevier Ltd. All rights reserved.
机译：超临界二氧化碳（SCO2）具有易于达到的伪临界点和热物理性质的优点，因此是制冷系统，能源利用和新的功率循环的极佳候选者。泪滴凹痕/突起作为一种有效的被动式热控制技术，在增强传热和降低电阻方面具有巨大潜力。在本文中，将三种类型的水滴凹痕和突起新颖地引入了SCO2矩形通道中。已经进行了数值计算以获得详细的流动结构，摩擦和传热特性，整体热性能以及在整个湍流区域下的熵产生量。此外，通过深入分析，讨论了几何结构，滴眼窝/凸起的偏心率，Re，SCO2的温度和压力的影响。根据结果​​，提出了三种不同结构的复杂而不同的涡旋演化和发展模式。正偏心凹痕（PED）产生了最佳的整体热性能，这归因于显着的传热增强和较少的摩擦，并且最大TP达到1.17，与光滑情况相比，提高了17％。偏心距的变化对PED结构的整体热性能和熵产生影响很小，而在正偏心距凸起（PEP）和负偏心距凸起（NEP）情况下起主要作用。但是，Re的增加不利于整体热性能。此外，CO2的温度和压力对PED情况下的整体热性能有重大影响，并且已捕获到相应的较高TP和热性能劣化区域，这有利于快速定位温度和压力的特定范围，并且耦合模式。具体地，可以在温度305 K和压力8 MPa附近获得大于6的最大TP。 （C）2019 Elsevier Ltd.保留所有权利。

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