Seyfi Girgin
Istanbul Technical University, Turkey
Title: An Investigation of heat transfer performance of rectangular plate-fin heat exchanger by using common flow up & common flow down configurations of vortex generators with different wings attack angle
Biography
Biography: Seyfi Girgin
Abstract
Statement of the Problem: The need of high performance of thermal systems in many engineering applications has increased. The convectional heat exchangers are generally improved by surface augmentation. There are two enhancement techniques of convective heat transfer for compact heat exchangers. One is to extend heat transfer surface area like a fin, the other is to increase heat transfer coefficient between solid surface and fluid such as using turbulators as vortex generators. The purpose of this study is to increase the intensity of secondary flow and reduce the size of wake regions in rectangular plate fin heat exchangers os as to increase to heat transfer coefficient to gain size and effectiveness. In this study, a new type of vortex generator called common flow up-common flow down and its various configurations reported.
Methodology & Theoretical Orientation: In rectangular channel, three configurations have been analyzed; common flow up, common flow down and mix type (both up and down) with 15-30-45 and 60-degree wings attack angle. The height of the vortex pair is half of the channel height.
Findings: 3D CFD results showed that 30-degree common flow up configuration provides the better heat transfer rate under the same inlet velocity and temperature. 15-45 and 60 degree increases the heat transfer rates about 26%-33% and 42% while 30-degree configuration gives 59% more heat transfer performance compared to channel without vortex generators. However, at that configuration, pressure drop penalty occurs which is about 34% more pressure drop compared to channel without vortex generators pairs. Results showed that wings attack angel play an important role in determining the heat transfer performance. In detailed results; Nusselt number, Reynolds number, pressure drop, heat transfer coefficient and corresponding vortex generator configurations are compared. Further studies can be based on the effect of length, height and placement of the vortex generators.
Figure 1: Velocity streamlines over 30-degree common flow up type heat exchanger
Figure 2: Velocity streamlines at z=5 and z=7 mm (30-degree common flow up)
Figure 3: Velocity contours at Re=2000, 30-degree common flow type