The matching effect of the cold-to-hot fluid on the thermohydraulic characteristics of heat exchangers using gyroid-typed triply periodic minimal surfaces

The triply periodic minimal surface (TPMS) is a potential candidate for constructing the next-generation heat exchanger (HEX) due to its considerably high specific area and flexible topology. Considering the flow rate and volume ratio of the cold-to-hot fluid domain, this work aims to probe the matching effect of the cold-to-hot fluid on the thermohydraulic features of cross-flow HEXs using gyroid TPMS structures. The results indicate that owing to the contiguous and intertwined path, TPMS structures induce a three-dimensional spiral flow with three typical flow characteristics (“merge-split,” parallel, and circulation) from different perspectives, dominating the fluid mixing and heat exchanger. The flow rate and volume ratio have a negligible influence on the thermohydraulic features but with different intensities. Increasing the cold-side velocity with a constant hot-side velocity can remarkably enhance convection heat transfer of the cold side with an increased pressure drop, while the hot side is influenced negligibly. Finally, the total heat transfer rate is gradually raised but reaches stability due to the limited hot-side heat transfer. A slightly higher flow rate ratio is recommended for improving HEXs. In comparison, the volume ratio simultaneously affects the fluid–solid interface area and internal fluid velocity under the mutual restriction between cold and hot fluids with an optimum volume ratio of Rvol = 1.0. With Rvol from 0.42 to 1.0, the heat transfer rate is increased by 7.7%, and the outlet temperature decreases by 1.5 K. Compared with the traditional structures, the gyroid structure offers a 100% higher specific surface area and 150%–225% higher volume-based power density.