汽车排烟余热回收强化换热管的数值模拟与分析

对汽车排烟余热回收装置的双斜向流线型内肋换热管进行了数值模拟研究,主要分析了内肋的结构特性参数对换热性能的影响。结果表明,流线型内肋在肋长、肋倾角、肋高度和肋间距上存在最优值,分别为38mm,45°,2.5mm和60mm。当Re=1.2×104～5×104时,与同条件下普通圆管相比,努塞尔数Nu可增加54.5%～90.7%,摩擦阻力系数f增加157.6%～204.2%;同时,双斜向流线型内肋管内场协同角从90°减小到80°,换热效果显著提升。运用场协同理论分析,发现管内场协同角在每一个内肋附近都出现骤减现象,并体现其为换热效果增强的主要原因。

Numerical simulation and analysis of enhanced heat transfer tube for heat recovery of vehicle exhaust

A numerical simulation is carried out for the analysis of Double-Inclined Streamline Ribs tube（DISR tube）which is used in vehicle exhaust heat recovery.The influence on the heat exchange performance by structural parameter is analyzed.The results shows that the DISR tube structural parameter exists the optimal value of rib length（l=38mm）,rib inclined degree（α=45°）,rib height（h=2.5mm）and rib pitch（P=60mm）.Comparing a DISR tube with a plain tube in the same condition and range of Reynolds numbers（Re=1.2×104~5×104）,the Nusselt number is enhanced up to 54.5%~90.7%,and the friction factor increases to 157.6%~204.2%.Meanwhile,when the field synergy angle was reduced from 90°to 80°,the heat transfer effect is enhanced significantly.The paper presents that the field synergy angle decline greatly near every ribs,which is the main reason for the heat transfer enhancement.