箭鱼形翅片微通道流动换热特性研究

Flow and Heat Transfer Characteristics of Swordfish Fin Microchannel

超临界二氧化碳布雷顿循环是第4代核能采用的新一代热能循环系统。紧凑式微通道换热器作为超临界二氧化碳布雷顿循环的高低温回热器,其流动换热特性直接影响整体热电转化的效率。降低回热器的流动阻力,同时维持较高的换热效率是微通道换热器优化设计的重要研究内容。箭鱼形翅片微通道设计借鉴仿生学原理,理论上可显著降低流动阻力。本文以超临界二氧化碳为流动工质,建立箭鱼形翅片换热器的模型并进行三维数值模拟,分析不同排列下的箭鱼形翅片设计对换热器流动换热特性的影响。同时对箭鱼形翅片设计与传统商用折线形微通道换热器流动换热特性进行对比分析。研究分析表明,在相同雷诺数下,箭鱼形翅片微通道的努塞尔数为折线形流道的2倍,而压降仅为其1/2,所以箭鱼形翅片微通道换热器的流动换热特性明显优于折线形换热器。通过优化分析,发现箭鱼形翅片设计最优的排列间距为沿流动方向的翅片间距La=8 mm,垂直于流动方向的翅片间距Lb=6 mm。

The supercritical carbon dioxide Brayton cycle is a new generation of thermal cycle used in the fourth generation of nuclear energy.As a high or low temperature recuperator of supercritical carbon dioxide Brayton cycle,the thermal hydraulic characteristics of the compact microchannel heat exchanger directly affect the power cycle efficiency.Reducing flow resistance of the temperature recuperator while maintaining high heat transfer efficiency is an important research for microchannel heat exchanger optimization design.The swordfish fin microchannel design considering bionics theory can significantly reduce the flow resistance.In this work,the swordfish fin heat exchanger model was established with supercritical carbon dioxide fluid as the flow medium.The effect of swordfish fin design with different arrangements on heat transfer characteristics was analyzed by three-dimensional numerical simulation.At the same time,the thermal hydraulic characteristics of swordfish fin design were compared with those of traditional commercial Z-shaped microchannel heat exchanger.The results show that under the same Reynolds number,the Nusselt number of the swordfish fin microchannel is twice as much as that of the Z-shaped microchannel,but the pressure drop is only half of that.Therefore,the thermal hydraulic performance of swordfish fin microchannel heat exchanger is obviously better than that of Z-shaped heat exchanger.It is obtained from optimization analysis that the optimal pitches for swordfish fin design is that the La=8 mm along the flow direction,and the Lb=6 mm perpendicular to the flow direction.