## 4 Conclusions  
This study investigated the effect of three distinct porous structures with varying pore sizes and geometries fabricated using binder-jetting 3D printing on pool-boiling heat transfer performance. Experiments were conducted using de-ionized and de-gassed water at atmospheric pressure. The main conclusions from this study are as follows:  
1. Superior performance of 3D-printed structures: The 3D-printed heat transfer surfaces consistently exhibited significantly better boiling heat transfer performance than the Sintered Plain surface, being particularly notable in the low heat flux region;
2. CHF and peak heat fluxes: * The Sintered Plain surface reached its CHF at 782 kW/m\({}^{2}\) at a wall superheat of 18.03 K. * The Staggered surface showed a substantial CHF enhancement, reaching 2342.4 kW/m\({}^{2}\) at a wall superheat of 24.6 K (approximately 199.7% higher than the Sintered Plain CHF). * Notably, Large Lattice and Small Lattice structures did not reach CHF within the tested range. Instead, these surfaces sustained high heat fluxes, reaching peak values of 2397.7 kW/m\({}^{2}\) (at a 55.6 K wall superheat) and 2577.2 kW/m\({}^{2}\) (at a 39.5 K wall superheat). These peak heat fluxes represent increases of approximately 206.8% and 229.7%, respectively, over the Sintered Plain CHF. 3.HTC Performance: * The Sintered Plain surface showed an increasing HTC trend up to a maximum of 43.34 kW/(m\({}^{2}\cdot\)K) corresponding to its CHF. * The Staggered surface exhibited a rapid increase in HTC at low heat fluxes, reaching a peak of 95.34 kW/(m\({}^{2}\cdot\)K) at its CHF of 2342.4 kW/m\({}^{2}\). * The Large Lattice and Small Lattice surfaces showed rapid HTC growth in the low to medium heat flux region, reaching their highest values early. Small Lattice peaked at 95.62 kW/(m\({}^{2}\cdot\)K) at a heat flux of 272.72 kW/m\({}^{2}\) (2.85 K wall superheat), while the Large Lattice peaked at 133.41 kW/(m\({}^{2}\cdot\)K) at 513.97 kW/m\({}^{2}\) (3.85 K wall superheat). Beyond these peaks, the HTC for the lattice structures decreased or flattened towards their maximum sustained values (the Small Lattice HTC was 65.3 kW/(m\({}^{2}\cdot\)K) at a heat flux of 2577 kW/m\({}^{2}\); the Large Lattice HTC was 43.14 kW/(m\({}^{2}\cdot\)K) at a heat flux of 2397 kW/m\({}^{2}\)). * At low heat fluxes, the structured surfaces significantly enhanced the HTC over the Sintered Plain. The Staggered surface showed an enhancement of up to 118.7% (approximately 2.04 times), the Small Lattice up to 119.3% (approximately 2.21 times), and the Large Lattice up to 206% (approximately 3.08 times). * Mechanisms for enhanced performance: The superior performance of the 3D-printed structures is attributed to their porous nature, which provides enhanced nucleation site density and facilitates effective bubble management. Interconnected porous cavities create separate pathways for liquid and vapor flow, with capillary forces being crucial in replenishing liquid to the heated surface. This capillary action, combined with potential wettability gradients (particularly in the lattice design), delays dry-out and sustains high heat fluxes. * Implications: This research clearly demonstrates the substantial improvement in pool boiling heat transfer achieved using porous copper surfaces fabricated via BJ3 DP technology. While the Staggered surface exhibited an impressive 199.7% enhancement in critical heat flux (CHF) compared to the plain surface, the Large Lattice and Small Lattice configurations showed an even more remarkable performance achieving 206.8% and 229.7% CHF enhancements at their highest recorded heat fluxes. These surfaces maintained stable boiling even under very high wall superheats, exhibiting extraordinary resistance to boiling crises. This significant finding highlights the potential of precisely engineered BJ3 DP porous structures to fundamentally alter boiling behavior, paving the way for next-generation thermal management solutions capable of stable operation under extreme heat flux conditions.