封头形状对板翅式换热器入口段流场影响的数值研究

Numerical study on effect of header’s curve of plate-fin heat exchanger on uniformity of entrance flow field

板翅式换热器入口段存在流场分布不均匀,并由此会引起换热效率低下。首先从封头曲线对流体的引导作用出发,进而优化换热器入口段流场均匀性,提出了板翅式换热器一次封头进一步的改进和优化思路和方法。即结合封头截面曲线函数及其导数特性,将前人提出的下抛物型一次封头改进为上抛物型和正切型,并利用CFD数值模拟方法对3种封头条件下换热器入口段的流场分布进行了对比研究。研究结果表明,使用后两种曲线的封头时,换热器入口段的物流分配更为均匀,在入口条件为7 m/s时,流速不均匀度由封头I的5.9分别下降到0.5和0.4;流速最大值与最小值之比由封头I的73.6分别下降到60.5和41.5。

The uniformity of entrance flow field results in the heat transfer efficiency of plate-fin heat exchanger.Two kinds of meliorative header construction of plant-fin heat exchanger based on the change of header＇s curve and the guidance for fluid in entrance were presented.Combined with the curve function and its differential equation,the upward parabolic type and tangential type were substituted for the downward parabolic type header.The flow field distributions of different inlet velocity of these header constructions,which were obtained by numerical simulation,indicated that under some certain velocity conditions,the uniformities in entrance flow of the upward parabolic type and tangential type were better than that of downward parabolic type header.While the inlet velocity is 7 m/s,velocity non-uniformity decreased from 5.9 to 0.5 and 0.4 respectively,and the ratio between the maximum and minimum velocity in the outlet plane decreased from 73.6 to 60.5 and 41.5 respectively.