Numerical investigation of hydrothermal performance of double pipe heat exchangers with corrugation configuration

•Enhanced geometry is introduced through the changing pipes into corrugated.•Increase in heat transfer rate is investigated.•For each Reynolds number, the optimal outer pipe diameter for maximum hydrothermal performance is introduced.•An optimal ratio of outer pipe diameter to inner pipe diameter is introduced at a specified Reynolds number. This paper investigates heat transfer in a counterflow shell-and-tube heat exchanger across three configurations: (i) smooth tubes (Case a), (ii) a corrugated inner tube with a smooth outer tube (Case b), and (iii) both tubes corrugated (Case c). The study models turbulent flows of cold air in the shell and hot water in the tube using the k-ωSST model, solving the governing equations with the finite volume method (FVM). Parameters such as pipe and corrugation geometry, Reynolds numbers (Re), outer tube diameters (Do), and the ratio of outer to inner tube diameter (Do / Dio) were examined. The results show that increasing the corrugation amplitude (α) and decreasing the corrugation pitch (p) significantly raise both the Nusselt number and the friction factor. For an inner tube diameter (Dio) of 120 mm paired with an optimal outer tube diameter of 170 mm at Re = 15,000, a thermal performance factor (TPF) of 1.32 is achieved, which is 25.5 % higher than with a 150 mm outer tube. The optimal Do / Dio ratio ranges between 1.3 and 1.6, with a maximum TPF increase of 72.8 % observed at a ratio of 1.6 compared to a ratio of 1.1. This study uniquely explores the impact of hydraulic diameter on hydrothermal performance in heat exchangers, introducing new insights into optimal design configurations.