Numerical investigation of thermal hydraulic performance of a automobile heat transfer tube with ellipsoid dimples

Abstract

The heat transfer tube is one of the key components affecting the heat transfer performance of automobile radiators. Proposes a new kind of heat transfer tube with ellipsoidal dimples based on the elliptical heat transfer tube. The effects of the arrangement and pitch ellipsoidal dimples on the turbulent heat transfer and flow resistance of the heat transfer tube are further studied by numerical simulation in the range of Reynolds number in 4080~24480. The results show that the ellipsoid dimple arrangement makes the near-wall fluid produce different flow forms, which enhances the turbulence degree of the tube fluid and thus improves the convective heat transfer capacity of the tube. Among them: vertical parallel arrangement (Case1) causes convergent flow, oblique parallel arrangement (Case2) causes helical flow, and diagonal symmetrical arrangement (Case3) causes cross-helical flow. The cross-helical flow causes the most significant degree of turbulence, followed by the helical flow. Furthermore, the arrangement and pitch of the ellipsoidal dimples also have an essential influence on the heat transfer performance and flow resistance of the heat transfer tube. The Nusselt number and Friction factor of Case1, Case2 and Case3 increase successively. But the Nusselt number and Friction factor gradually decrease with the rise of the pitch of ellipsoidal dimples. However, under different ellipsoidal dimples pitch, the comprehensive performance of Case1, Case2 and Case3 is better than that of smooth elliptical tubes. Among them, Case3 has the best performance when P=15mm, and the performance evaluation criteria value is up to 1.39.