磁场作用下椭圆管内铁磁流体的流动及传热特性

Flow and heat transfer characteristics of ferrofluid in elliptical tube under magnetic field

为了探索磁场对椭圆管内铁磁流体的流场及换热特性的影响,对其进行数值模拟研究。分析椭圆管道中磁场-流场-温度场之间的协同效应,并考虑不同雷诺数Re、磁场强度及椭圆管长短轴比对对流换热系数h及压降的影响。研究结果表明:由于磁场-流场-温度场的协同作用,铁磁流体在椭圆管内形成旋流流动,强化传热明显。对流换热系数随着雷诺数、磁场强度和椭圆管长短轴比的增大而增大。综合考虑流体换热和压降对换热性能的影响,在磁场强度较高、长短轴比值较小、雷诺数较低的情况下,磁流体流动和传热的综合性能较好,管型A0—A4的综合换热因子分别为1.456、1.447、1.429、1.393和1.35。

In order to investigate the influence of magnetic field on the flow field and heat transfer characteristics of ferromagnetic fluid in elliptical tube,numerical simulation was carried out.The synergistic effect between the magnetic field-flow field-temperature field in the elliptical tube was analyzed,and the effects of the Reynolds number,the magnetic field intensity and the length-to-short axis ratios of the elliptical tubes on the convective heat transfer coefficient and pressure drop was considered.The results show that the swirling flow is gradually formed in elliptical duct due to the coupling of thermal-magnetic-velocity fields,which enhances heat transfer significantly.The heat transfer coefficient increases with the increase of the Reynolds number,the magnetic field intensity and the length-to-short axis ratio.Considering the influence of fluid heat transfer and pressure drop on the heat transfer performance,the comprehensive performance of ferrofluid flow and heat transfer are better at higher magnetic field intensity,smaller long and short axis ratios and lower Reynolds number.The composite heat transfer factors of tube A0-A4 are 1.456,1.447,1.429,1.393 and 1.35,respectively.