双排平直翅片管换热器换热和流动性能的三维稳态模拟

利用三维稳态模拟研究了叉排和顺排布置形式、几何尺寸和雷诺数ReD对双排平直翅片管换热器换热和流动特性的影响。研究结果表明:尾流区面积是影响换热量的主要因素,其原因是尾流区的风速很小,部分空气无法被主流带走,造成了空气和翅片间的温差很小,努塞尔数NuD接近零;顺排管换热器前排管的尾流区较宽,并与后排管的连接形成宽度为D的尾流通道,形成了比叉排管换热器大的尾流区面积,因而前者的换热效果比后者差。在几何参数中,翅片间距对换热量的影响最为显著,因为翅片间距较大时,管前和管侧会产生向下游移动的马蹄形漩涡,显著强化了换热;流动方向或垂直于流动方向的管间距的减小,会增大前排管尾流区对后排管的影响,从而恶化传热。

Three-dimensional steady simulation of flow and heat transfer of two-row plate-fin and tube heat exchangers

Air flow and heat transfer of two-row plate-fin and tube heat exchangers for both staggered and in-lined tube arrays are studied when structural parameters and Reynolds are different.The results show that the ratio of a wake region is the most main factor affecting the heat transfer rate.The air in the wake is trapped and at low velocity.And the temperature difference between the air and the fin in it is very small.Thus,the Nu is very small there,close to zero.Moreover,the ration of the wake region for in-lined tube arrangement is higher than that for the staggered tube arrays.The wake of the first row tube is widened and connected with that of the second row tube for in-lined tube arrangement,which result in the greater wake area.Finally,the fin spacing of the geometric parameters has the most notable influence of the heat transfer rate.For bigger fin spacing,the horseshoe vortex system show up at the front of tube and extend towards the downstream.Correspondingly,the heat transfer is enhanced.However,for the smaller longitudinal and transverse tube pitches,the heat transfer around the second row tube is worse because the wake of the first row is closer and has more impact.