In the present study, the effects of the heights and widths of the hexagonal fins, streamwise and spanwise distances between fins. and flows velocity on the heat and pressure-drop characteristics were investigated using the Taguchi experimental-design method. Nusselt number and friction factor were considered as performance statistics, An L-18(2(*)(1)3(7)) orthogonal array was selected as the experimental plan for the five parameters mentioned above, While the optimum parameters were determined, the trade-off among goals was considered. First of all. each goal was optimized, separately. Then, all the goals were optimized together. Considering the priority of the goals, and the optimum results were found to be a fin width of 14 mm. a fin height of 150 mm, spanwise distance between fins of 20 nun, and streamwise distance between fins of 20 mm for a flow velocity of 4 m/s. (c) 2005 Elsevier Ltd. All rights reserved.