Flow optimization in a microchannel with vortex generators using genetic algorithm

Abstract

• The effect of different geometrical and flow conditions for microchannels with VGs. • Thermal-hydraulic performance of the microchannels with VGs is examined in details. • Response Surface Methodology is adopted for optimization work. • Pareto optimal solution is obtained from Multi-Objective Genetic Algorithm method. • Predictive sensitivity of the empirical correlations proposed for Nu and f is fairly well. In this study, delta winglet-type vortex generators, widely used in conventional macro channels and proven to be effective, are used in microchannels to increase their heat transfer capacities. The effects of vortex generators on heat transfer and pressure loss characteristics are studied numerically for different angles of attack, vortex generator arrangement type, the transverse and longitudinal distance between vortex generators, vortex generator length and height, and different Reynolds numbers. The thermal and hydraulic characteristics are presented as the Nusselt number, the friction factor, and the performance evaluation criteria number ( PEC ) that takes into account the heat transfer enhancement and the corresponding increase in pressure loss. The variation of Nu/Nu 0 , f/f 0 , and PEC are found to be in the range of 1.03–1.87, 1.04–1.8, and 0.92–1.62, respectively. A multi-objective optimization study are performed with the response surface methodology analysis to see how different parameters affect heat transfer and pressure loss and to determine the most optimum design. Besides, local sensitivity analysis study is carried out through the RSM, and water inlet velocity for heat transfer enhancement is found to be the most effective parameter. Among the geometric parameters, vortex generator height is determined as the most effective factor. Finally, practical Nusselt number and friction factor correlations taking many parameters into account are proposed to be able to compare the results of other researchers, and for engineers designing microchannel cooling systems.