Numerical optimization of a heat exchanger with slit fins and vortex generators using genetic algorithms

Abstract

Abstract Heat exchangers are devices very commonly found in heating and air conditioning appliances. This work is about the optimization of compact heat exchangers with three rows of tubes and slit fins, using built-in longitudinal vortex generators on the fins. The Colburn factor and the friction factor were obtained out of numerical simulations from a universe of 32 geometries. Geometries were selected using the Latin hypercube design, and were numerically simulated. Two objective functions were employed as surrogate models for the Colburn and friction factor. The functions were determined by multiple regression with a level of R square higher than 99.5%. A multi-objective numerical optimization was made, to find the best location for delta winglet vortex generators and its angle of attack; searching for an increase of heat transfer and a low value in pressure penalty. Group of optimal geometries was obtained, because of the optimization process using genetic algorithms. The geometry, with the best performance was simulated, and the results were used to validate the optimization process. This geometry, when compared to the slit fin without vortex generators (smooth condition), increased by 8.74% the heat transferred and augmented by 14.77% the pressure drop. The angle of attack, module, and module angle of the optimized geometry were 49.86°, 5.08 mm and 22.51° respectively.