Effects of surface defects on flow and heat transfer in additively manufactured ellipsoidal Kelvin lattices

Most studies on forced convection in ellipsoidal Kelvin lattices rely on ideal geometries or equivalent roughness, overlooking the combined influence of additive-manufacturing-induced surface roughness and geometric deviations. This study investigates the flow and heat transfer performance of AlSi10Mg ellipsoidal Kelvin lattices fabricated by selective laser melting (SLM). Six unit-cell configurations with strut diameters of 0.5–1.0 mm were fabricated and characterized using micro-CT, laser confocal microscopy, and point-cloud registration. The reconstructed geometries were used for CFD simulations and validated by wind-tunnel experiments on a 50 mm × 50 mm × 10 mm lattice under a constant heat flux of 40 kW/m 2 and inlet velocities of 5–20 m/s (Re ≈ 121–988). Experimental pressure-drop and heat-transfer results agreed well with numerical predictions. Characterization shows that the printed lattices exhibit manufacturing-induced roughness and slight geometric deviations, which modify local flow passages and consequently affect pressure loss and heat transfer. Their influence depends on strut diameter. For small struts (0.5 mm), roughness-enhanced near-wall mixing dominates, resulting in a 14% higher convective heat transfer coefficient than the ideal model at 20 m/s, although with increased pressure loss. For large struts (1.0 mm), geometric deviations become dominant, reducing the heat transfer coefficient by 14.9% compared with the ideal model. These results clarify the competing roles of surface roughness and geometric deviations in additively manufactured Kelvin lattices and provide guidance for the design and optimization of lattice heat exchangers.