正弦波微通道PCHE中超临界LNG流动换热研究

Study on supercritical LNG flow and heat transfer in sinusoidal wave microchannel PCHE

超临界LNG在正弦波微通道印刷电路板式换热器中流动换热时,因物性在拟临界点附近剧烈变化和涡流剪切作用的影响使流动换热过程更为复杂。采用数值模拟方法研究了在6组振幅模型下不同流量时各节距处Nu数、摩阻因子f、对流换热系数h、压降△P及综合换热性能评价因子PEC的变化规律,并提出面协同角概念来分析局部流动换热机理。结果发现:沿流向Nu数先上升后下降,峰值在拟临界点附近出现;由于湍流强度的增大,△P和h随流量的增大而提高;振幅和流量一定程度的增大有利于综合换热效果提升;相比于直流道,由于涡流剪切作用的增强,流体边界层变薄,速度/温度场协同性与流道曲率(振幅)呈正相关,速度/压力场协同性与流道曲率(振幅)呈负相关。

The flow and heat transfer process of supercritical LNG was more complicated due to the dramatic change of physical properties near the quasi-critical point and the influence of eddy shear in sinusoidal wave microchannel printed circuit board heat exchanger(PCHE).The variations of Nu number, friction factor f,convective heat transfer coefficient h,pressure drop △P and comprehensive heat transfer performance evaluation factor PEC at each pitch under 6 amplitude models with different flow rates were studied using numerical simulation method. The face synergy angle was proposed that analyzed mechanism of local flow and heat transfer.The results show that the Nu number first increases and then decreases along the flow direction. The peak value of Nu appears near quasi-critical point. △P and h increase with the improvement of flow rate due to the enhancement of turbulence intensity.To a certain extent, the increases of amplitude and flow rate are conducive to the improvement of comprehensive heat transfer effect. Compared with the straight channel, the fluid boundary layer becomes thinner due to the enhancement of eddy shear. The concordance of velocity and temperature field is positively correlated with the channel curvature(amplitude) of passageway. The concordance of velocity and pressure field is negatively correlated with the channel curvature(amplitude) of passageway.