汽车尾气温差发电器换热通道强化换热性能的数值模拟

On Numerical Simulation of Heat Transfer Performance of Heat Exchanger for Automobile Thermoelectric Generator

提出一种适合汽车尾气温差发电器的方型双面翅片换热通道结构,利用流体仿真软件FLUENT,在一定的尾气流速下,对该强化换热通道进行数值模拟.通过改变翅片结构特性尺寸(翅片长度l、间距d、高度h)进行仿真计算,得到不同翅片结构管道的壁面努塞尔数(Nu)、摩擦因子(f)以及综合换热效率(η),发现翅片换热通道的综合换热效率与翅片长度和高度成正比,与翅片间距成反比.综合考虑翅片结构特性尺寸的多因素影响,得到强化换热性能最优的翅片结构为l=400mm,d=20mm,h=50mm.

A numerical study has been undertaken for investigating the heat transfer enhancement in a rec-tangular channel with longitudinal fins for the automobile thermoelectric generator.The fins have been in-serted near the channel wall.Sixty-four kinds of fins in different dimensions (fin length l,fin spacing d, fin height h)have been considered.Uniform heat flux has been applied to external surface of the channel and air selected as working fluid.Number calculations have been performed with FLUENT code,in the range of flow rate(wi)10 m/s-50 m/s.The results obtained from a smooth channel have been compared with the finned channels,finding that the overall enhancement ratios increase with increasing fin length and fin height,also the overall enhancement ratios decrease with increasing fin spacing.Consequently,the variation of Nusselt number,friction factor and overall enhancement ratios for the channel with fins have been presented and best overall enhancement of 24.9% has been achieved for wi=10 m/s for which the fin dimensions is l=400 mm,d=20 mm,h=50 mm.