Experimental study on thermo-hydraulic performance of a novel envelope winglet vortex generator in a TEG hot-side engine exhaust heat exchanger

Abstract

The power output of the TEG system will be improved by using a surface roughness that is appropriate for enhancing the convection heat transfer coefficient. This study aims to conduct experimental research to ascertain the thermal and hydraulic impacts of novel envelope winglet-type longitudinal vortex generators (EWVGs) installed in a rectangular channel of a TEG hot-side heat exchanger. Using engine exhaust, the best design configuration for the thermo-hydraulic performance evaluation of EWVGs has been established regarding tilt angles (θ =30°, 45°, 60°, 90°) with various axis ratios in a longitudinal direction. Also, to observe the temperature and velocity profiles at various flow velocities, a numerical analysis of EWVGs has been conducted. The experimental result revealed that the EWVGs at θ =60° perform better in terms of heat transfer rate when compared to smooth ducts and has a 38.69% higher heat transfer rate than heat exchanger without EWVGs. The pressure drop increased along with the increase in tilt angle; hence, the pressure loss penalty for EWVGs was adversely affected. EWVGs installed at θ =45° have a higher thermal enhancement factor of 3 at an axis ratio of 0.3. The thermal-hydraulic performance, JF factor rapidly declines along the heat exchanger’s longitudinal axis, and the EWVGs of θ =90° have the lowest JF factors. Furthermore, an optimum cost–benefit ratio (CBR) obtained at x/L of 0.4 and the CBR of EWVGs at θ =45°, has 43.17%, 74.23%, and 85.83% higher CBR than EWVGs at 30°, 60°, 90°, respectively. As a result, the heat exchanger’s unique EWVGs can improve thermo-hydraulic performance compared to those without them. Also, studies have shown the benefits of using VGs over smooth heat exchangers without VGs in the form of increased heat transfer rates. An extensive comparative analysis is carried out for this new shape for different configurations (tilt angles and velocities). © 2023, Akadémiai Kiadó, Budapest, Hungary.