新型扭带在层流中强化传热性能的数值模拟研究

提出一种新型的正反两个方向交替扭转的扭带模型,并基于ANSYS FLUENT软件在层流状态下(Re=400～18 00)对换热管中插入新型扭带的换热特性、流体阻力特性和综合性能指标进行数值模拟研究。对y=3.0,4.5,6.0三种扭率下的无缺口正反扭转扭带与传统单一方向扭带进行对比研究,并对扭率y=3.0的无缺口正反扭转扭带和带有三角、半圆及方形缺口的正反扭转扭带进行了对比计算。研究结果表明:插入不同扭率的扭带,换热管的努赛尔数Nu、摩擦系数f与综合性能PEC值均随着扭率的减小而增大;相同扭率下无缺口的正反扭转扭带在强化换热效果和综合性能表现上要优于传统扭带;扭率为3.0时,无缺口的正反扭转扭带比带三种缺口的正反扭转扭带换热效果好,而缺口的存在可以大幅度地降低插入扭带产生的摩擦阻力,且缺口的面积越大,摩擦和换热效果降低越多。

Numerical studies on heat transfer enhancement of a new type of twisted tape in laminar flow

A new tape of twisted tape is presented which has alternateLYrotation in left and right two directions. Numerical investigation based on ANSYS FLUENT are carried out on characteristics of heat transfer, fluid flow and performance evaluation criteria (PEC) in heat exchanger with this new twisted tape for laminar flow (Re=400-1800). The comparison of typical twisted (TT) and Left and Right twisted tape (LRTT) without cut with twisted ratio 3.0, 4.5, 6.0 has been studied together with the comparison of LRTT without cut and LRTT with triangle, semicircle and square cuts with twisted ratio 3.0. The results show that the Nusselt numbers, friction factors and PEC are increased with decreasing of twist ratio. The heat transfer enhancement and PEC of LRTT without cut are better than that of TT with same twist ratio. Heat transfer effect of LRTT without cutsisbetter than that of LRTT with three type of cut, while the existence of the cuts can extremely reduce friction resistance with for LRTT. And the friction resistance and heat transfer are reduced with increasing area of cuts.