Heat transfer characterization of waste heat recovery heat exchanger based on flexible hybrid triply periodic minimal surfaces (TPMS)

Heat exchangers(HX) based on triple periodic minimal surfaces (TPMS) show superior heat transfer performance to conventional structures due to extremely high surface area-to-volume ratios and complex geometrical topologies. While current studies primarily examine flow and heat transfer within original TPMS structures, research on hybrid TPMS structures is limited. Therefore, this study aims to construct flexible hybrid TPMS structures based on the original TPMS structures by sigmoid transition parameters and to analyze their internal flow and heat transfer mechanisms in depth, as well as to comprehensively evaluate the heat transfer performance of several TPMS original structures and hybrid structures based on the complex proportional assessment (COPRAS) method. The results show that the unique topology of TPMS induces a continuous change in the internal fluid flow direction, which significantly enhances the convective heat transfer. Gyroid-Diamond TPMS HX had the highest heat exchange efficiency of 37.78%. the convective heat transfer coefficients of Primitive-Gyroid and Primitive-Diamond HX were increased by 47.31% and 67.38%, respectively, compared with the Primitive HX. In addition, Gyroid-Diamond HX exhibits the highest convective heat transfer coefficient of 2380.15 W/m(2)center dot K at a = 0.5, relative density of 40%, but also results in a relatively large pressure drop.