横置正弦型凹穴微通道中超临界LNG流动传热特性研究

Study on heat transfer characteristics of supercritical LNG in transverse sinusoidal concave microchannels

为强化印刷电路板式换热器(PCHE)中超临界LNG强化换热特性,基于处理表面强化换热技术,提出一种正弦型凹穴矩阵微通道模型,并对超临界LNG在其内部流动换热特性进行数值模拟研究。研究了不同凹穴结构阵列微通道流动换热性能和入口质量流量、正弦型凹穴高度和重力对范宁摩阻系数、对流传热系数及综合换热评价因子的影响,最后引入壁面平均涡强对正弦型凹穴局部流动与换热机理分析。结果表明:正弦型凹穴能够强化超临界LNG换热特性,换热效果与入口质量流速成正比,且环向横置阵列优于环向竖置阵列;凹穴高度增加,微通道中流动传热系数也随之增大;通过对比施加不同方向的重力对通道的流动换热影响,施加逆流方向的重力可以强化正弦型凹穴微通道的流动换热特性;结合综合换热评价因子分析,正弦型凹穴能够显著强化通道流动换热性能,并且凹穴高度0.2 mm阵列微通道换热性能最佳;通过壁面平均涡强分析正弦型凹穴通道局部流动换热机理,其能够产生强力漩涡使边界层变薄,对主流区域恶化程度低,能够加速热量由壁面向主流区传递,实现微通道表面强化换热。

In order to enhance the heat transfer characteristics of supercritical liquefied natu-ral gas(LNG)within printed circuit heat exchangers(PCHE),a surface enhancement heat transfer technique was employed.A sinusoidal cavity matrix microchannel model was proposed,and nu-merical simulations were conducted to investigate the internal flow and heat transfer characteristics of supercritical LNG.The influence of different cavity array microchannel flow structures,inlet mass flow rate,sinusoidal cavity height,and gravity on the friction factor,convective heat transfer coefficient,and overall heat transfer performance evaluation factor(PEC)was studied.Further-more,the analysis introduced the effect of wall-averaged vorticity strength on the local flow and heat transfer mechanisms of the sinusoidal cavity microchannels.The results indicated that the si-nusoidal cavity design could enhance the heat transfer characteristics of supercritical LNG.The heat transfer performance was directly proportional to the inlet mass flow rate,with a preference for a circumferential horizontal array over a circumferential vertical one.As the cavity height in-creased,the flow heat transfer coefficient within the microchannels also increased.The application of gravity in different directions demonstrated that imposing gravity in the opposite direction could strengthen the flow and heat transfer characteristics of the sinusoidal cavity microchannels.In con-junction with PEC analysis,the sinusoidal cavity design significantly improved the flow heat trans-fer performance within the channels,with an optimal cavity height of 0.2 mm in the array micro-channels.Through an analysis of wall-averaged vorticity strength,it was found that the sinusoidal cavity channels produced strong vortices that thinned the boundary layer,resulting in minimal deg-radation of the mainstream flow region.This design facilitated the accelerated transfer of heat from the wall to the mainstream flow region,thus achieving enhanced surface heat transfer within the microchannels.