Evaluation of Vortex Generators in the Heat Transfer Improvement of Airflow through an In-Line Heated Tube Arrangement

Syaiful Syaiful,Tri Wahyuni,Nazaruddin Sinaga,Bambang Yunianto

doi:10.3390/fluids6100344

Abstract

Improving heat transfer from surface to airflow is a current research concern for enhancing energy efficiency. The use of vortex generators for improving heat transfer from the surface to the airflow is very effective. Therefore, this study focuses on applying flat and concave vortex generators with and without holes in order to improve heat transfer. In this study, the number of pairs of vortex generators was varied from one to three pairs at a certain angle of attack for various forms of vortex generators. The airflow velocity through the duct was varied in the range of 0.4 to 2.0 m/s at 0.2 m/s intervals. From the investigation results, we observed that the highest thermal performance was found with the use of concave delta winglets without holes for various pairs of vortex generators in terms of the overall Reynolds number. The highest thermal enhancement factor was found to be around 1.42 at a Reynolds number of approximately 9000. From this study, it was also shown that the lowest cost–benefit ratio was about 1.75 at a Reynolds number of approximately 3500 for three pairs of vortex generators.

Highlights

Fin and tube condensers are widely used in household air conditioning, power generation, and the chemical industry
It was found that the addition of pairs of vortex generators (VGs) was able to increase the rate of heat transfer, as indicated by the increase in the Nusselt number ratio with the rise in the number of pairs of VGs at the same Reynolds number
The main reason for this is that the addition of pairs of VGs increases the number of longitudinal vortex (LV) generated and strengthens the LV [18]

Summary

Introduction

Fin and tube condensers are widely used in household air conditioning, power generation, and the chemical industry. Li et al [6,7] numerically and experimentally studied the effect of using a vortex generator on increasing heat transfer in a finless heat exchanger. The longitudinal vortex (LV) produced by the winglet-type VG can enhance heat transfer better than the transverse vortex (TV) produced by the wing-type VG [9]. This is due to the three-dimensional flow from the LV with the rotation axis in the direction of the main flow, resulting in a better mixing of the flow than that from the TV [10]. Mixing the cold fluid flow away from the wall with the hot fluid flow near the wall results in increased heat transfer [11]

Methods

Results

Conclusion