超临界二氧化碳在微细管内的换热特性

Heat transfer characteristics of supercritical carbon dioxide in a micro-capillary tube

建立了内径为1.31mm单管的三维模型,使用CFD软件Fluent分析了超临界二氧化碳在竖直微细管道内的换热特性,并对热通量、进口质量流速、流动方向和压力对超临界二氧化碳换热和压降的影响进行了研究。数值结果表明:增加进口质量流量能够使壁面边界层减薄,增强换热效果。改变热通量的大小对超临界二氧化碳换热和压降影响很小。由于重力和浮升力的影响,流动方向对换热性能的影响较大,流体竖直向上流动时的传热系数大于竖直向下和水平方向流动时的传热系数。

Three-dimensional model of single tube with an inner diameter of 1.31 mm was established; using CFD software Fluent,the flow and heat transfer characteristics of supercritical carbon dioxide in the micro-capillary tube was analyzed.The influences of the heat flux,inlet mass flow rate,flow direction and pressure on the heat transfer of supercritical carbon dioxide and pressure drop are analyzed.It was shown that:boundary wall thinning by increasing the import mass flow rate;which could enhance heat transfer. Changing the heat flux has little influence on heat transfer and pressure drop of supercritical carbon dioxide.Due to the effects of gravity and buoyancy,the impact of the flow direction on the heat transfer performance was large;the heat transfer coefficient of vertically upward fluid flow is greater than that of the vertical downward flows and horizontal flow.