Correlations and shape optimization in a channel with aligned dimples and protrusions

In this study, the friction factor and Nusselt number in a plate heat exchanger with dimples and protrusions were investigated according to geometric and operating conditions. The numerical results of a steady-state laminar model for the laminar region and a steady-state SST (shear stress transport) k-ω turbulence model for the turbulent region were in good agreement with an unsteady analysis. For efficient analysis, a correlation for the critical Reynolds number was derived as a function of the geometric parameters. Based on these results, Nusselt number and friction factor correlations applicable to various geometric parameters and operating conditions (500 ⩽ ReH ⩽ 15,000) were obtained. Multi-objective optimization was carried out, where the objective function was a function of the normalized Nusselt number and normalized friction factor. To investigate the variation of the optimal points according to weighting factors, a Pareto front was generated using a micro-genetic algorithm. When JF factor was used as a single-objective function, the performance of the optimal point was enhanced by 28% compared with that of the reference model. The optimal point was independent of the Reynolds number.