非对称紧凑式换热器内超临界二氧化碳与液态铅铋合金耦合换热特性研究

Coupled heat transfer characteristics of supercritical carbon dioxide and liquid lead-bismuth-eutectic in asymmetric compact heat exchange

超临界二氧化碳布雷顿循环与铅冷快堆的结合被认为是最为理想的动力循环之一,系统通过中间换热器传递热量,其性能影响着整个发电系统的高效与安全运行。由于超临界二氧化碳和液态铅铋合金(LBE)物理性质和热输运性质差异显著,对称式结构无法匹配两侧工质的换热要求,构建了1种非对称式紧凑式耦合换热器,采用数值模拟方法研究了超临界二氧化碳与液态铅铋合金耦合换热特性。结果表明:提升冷侧流体入口速度会显著增强换热;增加热侧LBE入口速度时,总换热系数先降低后增加;提升换热器冷热流体入口温度,换热器的换热系数先减小后增大,存在最优值;在拟临界区内,强浮力作用会大幅提升冷侧换热,而加速效应则抑制换热。

The combination of supercritical carbon dioxide Brayton cycle and lead cooled fast reactor is considered as one of the most ideal power cycles.The system transfers heat through the intermediate heat exchanger,and its performance affects the efficient and safe operation of the whole power generation system.Due to the significant differences in physical properties and heat mass transport properties between supercritical carbon dioxide and liquid lead bismuth eutectic,the symmetrical structure cannot match the heat transfer requirements of the working fluids on both sides.In this study,an asymmetric compact coupled heat exchanger was constructed,and the coupled heat transfer characteristics of supercritical carbon dioxide and liquid lead bismuth eutectic were studied by numerical simulation.Increasing the inlet velocity of the cold side fluid will significantly enhance the heat transfer;When the inlet velocity of LBE at the hot side is increased,the total heat transfer coefficient first decreases and then increases;When the inlet temperature of the cold and hot fluid of the heat exchanger is increased,the heat transfer coefficient of the heat exchanger first decreases and then increases,and there is an optimal value;Due to the high proportion of thermal resistance in the cold side,the similarities and differences of heat transfer characteristics of cold side supercritical carbon dioxide under buoyancy and thermal acceleration under different operating parameters are compared;It is found that in the quasi critical region,the strong buoyancy will greatly enhance the cold side heat transfer,while the acceleration effect will inhibit the heat transfer.