Contents lists available at ScienceDirect International Communications in Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ichmt Optimization of geometry and nano-fuid properties on microchannel performance using Taguchi method and genetic algorithm Seyed Morteza Javadpour a,1 , Elyas Abbasi Jannat Abadi b,1 , Omid Ali Akbari c , Masoud Goharimanesh d, ⁎ a Mechanical Engineering Department, University of Gonabad, P.O. Box 9691957678, Gonabad, Iran b Young Researchers and Elite Club, Mashhad Branch, Islamic Azad University, Mashhad, Iran c Young Researchers and Elite Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran d Mechanical Engineering Department, University of Torbat Heydarieh, P.O. Box 9516168595, Torbat Heydarieh, Iran ARTICLE INFO Keywords: Nanofuids Ribbed microchannel Genetic algorithm SNR ABSTRACT The aims of the present study are to develop and validate a new numerical model to estimate Nusselt number and friction factor as a function of ribbed length, rib's height, the distance between each rib, and nanoparticle volume fraction. For this, heat transfer of water-based Al 2 O 3 nanofuids in laminar fow conditions via a ribbed mi- crochannel with triple and fourth rib shapes of triangular, rectangular, and trapezoidal under a constant fux of heat was considered numerically by implementing fnite volume scheme. Three-dimensional simulations were performed using design nodes appointed systematically by Taguchi method within a rectangular microchannel with a length of 4 mm and a height of 50 μm. The problem is subjected to maximization and minimization of the Nusselt number and friction factor of the microchannel, respectively. Based on the design parameters in the Taguchi method continuous approximation functions for Nusselt number and friction factor were developed. Finally, a multi-objective genetic algorithm was exploited to detect the optimum solutions of Pareto in a multi- criteria diagram. Utilizing this diagram, designers could gather the information required for a trade-of between each criterion and design a microchannel that best fulflls their needs. The maximum error of 4% for Nusselt number and 16% for friction coefcient which was confrmed by CFD simulation show the efciency of the Pareto front prediction. 1. Introduction The properties of nanofuids (NFs) have been studied extensively in recent years due to their productive roles in industrial sections, such as improving the efciency of many energy systems [1]. One of the most critical problems in the use of NFs is preparing and fabricating, which are time and cost consuming. Fortunately, numerical methods could attract the attention of the researchers to overcome these challenges. However, there is a gap between numerical results and experimental achievements [2]. Microchannels (MCs) as the road of NFs are eye-catching in heat sink devices, especially the interrupted ones, which are fabricated by ribs or fns to improve the transfer of heat. The geometry of ribbed- microchannels (RMCs) and the properties of NFs used are the most important factors to design an efcient MC, which is successful in maximizing the average Nusselt number and the minimizing the coefcient of friction. Behnampour et al. [3] studied hydrodynamic and heat transfer behavior of laminar water-based silver NF in MCs by three shapes of ribs, triangular, rectangular, and trapezoidal. They presented that rectangular rib has a lower average Nusselt number compared to trapezoidal one, and triangular rib causes to the lowest coefcients of friction. Akbari et al. [4] studied how rib height can increase the rate of heat transfer. They used a laminar water/ Al 2 O 3 NFs fow in a two- dimensional rectangular MC. They revealed, increasing the height of the rib and the proportion of nanoparticles (NPs), simultaneously rises the coefcient of friction, average Nusselt number, and rate of heat transfer of the RMCs. Abdollah et al. [5] investigated simulation of laminar heat transfer forced convection in a heat sink with an elliptical and diamond RMCs numerically. They showed ellipse ribs perform more efciently than diamond ribs. Shamsi et al. [6] analyzed the fow of the non-Newtonian NFs of water/CMC/Aluminum oxide in triangular RMCs. They investigated the efect of triangular ribs with three https://doi.org/10.1016/j.icheatmasstransfer.2020.104952 ⁎ Corresponding author. E-mail address: m.goharimanesh@torbath.ac.ir (M. Goharimanesh). 1 These authors contributed equally to this work. International Communications in Heat and Mass Transfer 119 (2020) 104952 0735-1933/ © 2020 Elsevier Ltd. All rights reserved. T