Performance analysis and multi-objective optimization for tubes partially filled with gradient porous media

Abstract Based on the excellent performance of porous media and the popularity of additive manufacturing technology, gradient porous media with unique properties are gradually applied in the increasing fields. In this paper, the flow and heat transfer characteristics for fully developed flow in a tube partially filled with gradient porous media are investigated by numerical simulation, where the pore-size (dp) and porosity (e) vary linearly along the radius. Keeping average pore-size dpa = 0.007 m and average porosity ea = 0.875, the comparison of four configurations, classified by the pore-size and porosity distributions in the radial direction, is performed to investigate the difference in flow and heat transfer performance. Subsequently, the parametric analysis under the different filling ratios is conducted to learn the combined effect of the gradients of porosity and pore-size. The results show that the configurations with pore-size decreasing in radial direction have a better heat transfer performance where the effect of porosity arrangement on the flow and heat transfer can be neglected. As the filling ratio increasing, the performance is more sensitive to the variation of the gradients. Furthermore, a multi-objective genetic optimization coupled Kriging surrogate model is conducted with the consideration of maximum Nusselt number Nu and minimum friction factor f as objectives. The distribution of design variables corresponding to the optimal configurations is obtained by weighing two optimization objectives. The optimal results show that the flow resistance can be reduced by up to 19.573%, and the heat transfer efficiency can be increased by up to 7.088% compared with the homogeneous porous media under the filling ratio rd = 0.7.