A double pipe heat exchanger with outward helically corrugated tube is numerically studied and optimized. Under the determined geometry parameters of the corrugated tube, the parameter of the shell side is desired to obtain. Also, the mechanism of enhanced heat transfer and complex flow features on the shell side is investigated and compared with the tube side. Matching flow rates of tube and shell sides are solved by a multi-objective optimization method concerning simultaneously the heat transfer performance, pressure drop and energy benefit. It was found that, the variation tendencies of local heat transfer and pressure drop on tube and shell sides are exactly the same, and both the heat transfer and pressure drop are increased with decreasing the shell diameter. For a comprehensive consideration, the shell diameter of 38 mm is the best parameter to obtain a high heat transfer coefficient, and a low pressure drop. The optimal solutions of the matching flow rates on tube and shell sides are obtained by the genetic algorithm, and two equilibrium solutions are obtained for the tube and shell sides. (C) 2019 Elsevier Ltd. All rights reserved.