科研之友
微信
新浪微博
Facebook
分享链接
摘要
As an effective technology to reduce flow resistance, drilling holes on the surface of vortex generators had been studied extensively. In this paper, thermal performance of punched rectangular winglet vortex generators (PRWVGs) in turbulent regime (Reynolds number was in the range of 9, 090 similar to 21, 210) was studied experimentally and numerically. Air was applied as the working fluid. The PRWVGs were inserted into the tube with three attack angles (alpha = 30 degrees, 45 degrees, 60 degrees). The punched holes were set in three different positions (g = 3mm, 5mm, 7mm) in the vertical direction and at three different hole heights (d = 1mm, 3mm, 6mm). The performance of PRWVGs was quantified by the heat transfer coefficient ratio (h/h(0)), the friction factor ratio (f/f(0)), and a combined thermal enhancement factor (TEF) of the two. The results revealed that h/h(0) as well as f/f(0) values of PRWVGs compared with those of planar VGs (without holes) were reduced. The flow and temperature fields of different cases were obtained by numerical simulations, and the experimental results were verified by analyzing the fluid flow behaviors. The results showed that the jet flow (defined as a jet emanating from the punched hole of a VG), would enhance the heat transfer efficiency in the recirculation area. And the TEF value of VGs was improved by punching holes on the surface of VGs. However, the shape of the jet flow depended on the position of the hole. When the position of the hole was lower in the vertical direction, the jet flow was effective in increasing its TEF value. Additionally, the size of the hole had a large effect on the TEF value. Besides, entropy generation analysis showed that PRWVGs were thermodynamically advantageous. Whend = 1 mm, w = 5 mm, the Bejan number reached the minimum. Under this condition, the proposed PRWVGs performed best in practice. When the height of the hole was d = 1 mm, TEF was the maximum, which was 1.25 at alpha = 45?degrees and Re = 9,090.
-
单位衢州学院; 1
