Parametric analysis of the influence of geometric variables of vortex generators on compact louver fin heat exchangers

Abstract

This paper studies the performance of vortex generators (VG) in compact louvered fins and tubes heat exchangers. CFD simulations and genetic algorithm optimization were used to create surrogate models for the Colburn and friction factor of the heat exchanger as a function of VG positioning, size, and angle of attack. The models were used to study how the design parameters affects heat transfer enhancement and pressure losses. The study was conducted with a Reynolds number of 208 based in the hydraulic diameter of the flow channel. It was found that the performance of the VG in the first row of tubes is coupled to the aspect ratio of the VG of the second row of tubes. Further that vortex generators with large angles of attack produce recirculation areas behind them diminishing the heat transfer. Also, that best performing vortex generators correspond to small aspect ratios. Yet, these produce a low impact on the heat transfer enhancement when their angles of attack are greater than 50°. Vortex generators with large aspect ratios produce no significant effects on the heat exchanger performance. Larger vortex generators produce stronger and more intense vortices, greater drag, and frictional losses. This work shows how the different parameters of the VG affect heat transfer and pressure losses. The optimal model presents a PEC value of 1.055, in correspondence with a j/j0 ratio of 10.43 and a f/f0 ratio of 14,38.