过渡流状态下圆柱列流动与传热特性的数值模拟

Study on Flow and Heat Transfer Effect of Middle Row Cylinders to Front-Row and After-Row Cylinders in Transition Flow

紧凑型换热器的管径变细,管径细化后,换热器内的管外流动由湍流向过渡流转变,而对过渡流的研究较少。为了研究过渡流状态下管束的传热强化机理,采用基于复合网格系统的计算方法对两列顺排圆柱列与三列叉排圆柱列进行数值模拟,并对比研究流体与温度对流动传热特性的影响。数值模拟结果表明:当中间圆柱列不加热时,整流作用与尾流不稳定性作用的共同影响能够保证流动传热强化效果;当中间圆柱列加热时,温度场发生的变化会弱化传热。

The tubes of the compact heat exchangers are thinner.The trend of miniaturization of the heat exchangerresults in the changing of flow field outside the heat exchanger tubes from turbulent flow to transitional flow.There are less studies about the transitional flow.A numerical simulation and relative analysis of two models is carried out to research the enhancement mechanism of heat transfer.The calculation method is based oncompound grid. The results show that： The middle row cylinders has tinny influence on front-row cylinders but has strong influences on after-row cylinders. The strong influences are as followed：（1）Whenthe middle row cylinders areunheated,the rectifying effect together with the effects of the wake flow instability ensure flow and heat transfer enhancement.（2）When the middle row cylinders are heated,the temperature field change will deteriorate flow and heat transfer.