Study on flow and heat transfer characteristics of a D-type triple-period minimal surface heat exchanger

Rising thermal loads in aircraft engines and onboard systems demand efficient compact heat exchangers. D-type three-period minimal surface (TPMS) offers high specific surface area, smooth continuous surfaces, and favorable parametric design. We numerically study flow and thermal behavior in a D-type TPMS heat exchanger, focusing on vortex evolution, heat-transfer intensification, and asymmetric hot/cold channel responses to hot-side velocity. Periodic D-type geometry generates four vortex tubes at flow junctions. Their downstream re-pairing enhances radial mixing and disrupts thermal boundary layers, maintaining large wall temperature gradients and improving heat transfer but causing flow losses. Wall heat flux depends jointly on both streams. Increasing hot-side inlet velocity strengthens hot-side convection but deteriorates cold-side heat transfer due to higher near-wall temperature and thickened cold-side boundary layers. j-F factor quantifies the trade-off: higher hot-side velocity boosts convection yet amplifies pressure penalty, lowering efficiency under asymmetric flow. This reveals flow–heat coupling mechanisms for aerospace thermal management.