叉排板束换热器传热特性数值研究

Numerical Study on Heat Transfer Characteristics of Cross Row Plate Bundle Heat Exchanger

为提高换热器的传热性能,设计了叉排板束换热器,利用Fluent软件中的RNG k-ε模型数值研究了叉排板束的传热特性。分析了叉排板束排数对于整体Nu的影响以及板束的局部传热特性,比较了不同横纵比对整体Nu的影响,并给出不同Re下叉排板束的Nu经验公式。实验结果表明:叉排板束整体传热性能随板排数的增多而增强,当达到一定排数后传热性能趋于稳定,不同Re下趋于稳定的排数不同,当Re=4.3×10^(5)时进入稳定阶段需13排,当Re=4.3×10^(3)时进入稳定阶段仅需7排;叉排板束局部传热性能在各板排中先增大后减小,在第2~4排局部Nu达到峰值,板的局部传热性能在两个直角处以及撞击点位置大大增强;板束在横纵比为5时传热性能最佳,横纵比大于或小于5时,传热性能均会减弱;给出Re在1~500,500~1 000,1 000~200 000范围内板束整体Nu拟合公式,当Re>30 000时,与叉排圆管束相比,叉排板束传热性能提高25%。

In order to improve the heat transfer performance of the heat exchanger,a cross row plate bundle heat exchanger is designed.Using RNG k-εmodel in Fluent software,the heat transfer characteristics of cross row plate bundles are studied numerically.The influence of the number of plate rows on the overall Nu and the local heat transfer characteristics of plate bundles are analyzed.The effects of different aspect ratios on the overall Nu are compared,and the Nu empirical formulas of cross row plate bundles at different Re are given.The experimental results show that the overall heat transfer performance of the cross row plate bundle increases with the increase of the number of plate rows.When a certain number of rows are reached,the heat transfer performance tends to be stable,and the number of rows tending to be stable at different Re is different;when Re=4.3×10^(5),rows are required to be 13 to enter the stable stage,and only 7 rows are required to enter the stable stage at Re=4.3×10^(3);the local heat transfer performance of the cross row plate bundle first increases and then decreases in each plate row,and the local Nu reaches the peak approximately from row 2 to 4.The local heat transfer performance of the plate bundle is greatly enhanced at two right angles and the position of the impact point;When the aspect ratio is 5,the heat transfer performance of plate bundle is the best,and when the aspect ratio is greater than or less than 5,the heat transfer performance will be weakened;the overall Nu fitting formula of plate bundle is given when Re is in the range of 1 to 500,500 to 1000,1000 to 200000.When Re is greater than 30000,the heat transfer performance of cross row plate bundle is improved by 25%compared with the cross row circular tube bundle.