Porous supercritical transpiration cooling characteristics of triply periodic minimal surface

• Transpiration cooling mechanisms of triply periodic minimal surface porous. • Step-like pressure drop and oscillatory temperature rise occur in through-flow channel. • Increased coolant mass flow rate delays temperature oscillation. • Diamond structure achieves the highest average cooling efficiency. Transpiration cooling technology is crucial for thermal protection in extreme environments such as rocket engine combustion chambers. Triply periodic minimal surface (TPMS) structures have demonstrated significant potential in this field due to their excellent comprehensive performance; however, the underlying flow and heat transfer mechanisms at the pore scale remain unclear. To address this, six TPMS porous structures with different topological configurations were constructed in this work, and the transpiration cooling process of supercritical methane within them was simulated using a real-gas model. The results indicate that the flow channel topology is a key factor influencing performance: structures with through-flow channels (P-A, P-B, IWP-A) exhibit step-like pressure drops and oscillatory temperature rises, accompanied by higher flow resistance. In contrast, structures with only bypass flow channels (IWP-B, D, G) demonstrate smooth pressure drop and temperature rise curves, along with lower flow resistance. Under low coolant flow rates, the maximum wall temperatures of IWP-B, D, and G structures (204.3 K) were significantly lower than those of through-flow channel structures, indicating superior cooling performance. Under the same heat load, the D structure achieved the highest average cooling efficiency of 78.2 %. These findings highlight that TPMS structures with bypass flow channels can simultaneously achieve high cooling efficiency and low flow resistance, providing an optimal design solution and theoretical foundation for high-performance transpiration cooling systems.