Giacomo Tosatti, Sandra Corasaniti, Michele Potenza, Ivano Petracci
Abstract: The compactness of electronic devices and mechanical components and the constant increase in power density pose significant challenges in thermal management. These geometric constraints imply a reduced length of the channels dedicated to cooling, hence the need to properly analyse the conjugate heat transfer problem and develop innovative heat dissipation systems, such as lattice structures. This paper aims to numerically investigate the thermo-fluid dynamics properties of a short, empty duct, hence with porosity φ = 100%, named K0, 80 mm long, with a cross-section of 15 x 5 mm, in two different flow conditions: fully developed and developing flow. Then, the same channel is equipped with a Kagome-truss lattice with a truss diameter of 0.8 mm, designated as K1, characterised by a porosity of φ = 87%, and the analysis is repeated for both outflow conditions. The fluid is air, and the operating Reynolds numbers range from 2852 to 17115, thus falling within the transitional flow regime. Results for the smooth duct demonstrate its sensitivity to flow conditions, revealing a substantial increase in the Nusselt number by up to 13% at the cost of a higher friction factor, as expected from existing studies available in the literature. On the contrary, no significant variation in both the friction factor and the Nusselt number is observed for the K1, suggesting that its thermo-fluid dynamic properties are more influenced by the lattice structure rather than the flow profile. Finally, the two ducts are compared in terms of energy efficiency, evaluated as Nu/λ1/3, revealing that at the same Reynolds number, the efficiency of the Kagome duct is up to 2.2 and 2.4 times greater than that of the empty duct in fully developed and developing flow conditions, respectively. After the independence of the entry length for the K1 duct had been verified, the analysis was extended to two additional porosities, namely 96% and 76%, to assess whether an optimum in heat exchange and energy efficiency could be found. Results showed that increasing the pillar diameter leads to higher heat while leaving the flow pattern unchanged; however, the rise in pressure drop causes a saturation of the energy efficiency.
Keywords: RANS Numerical Simulations; Conjugate Entry Length Problem; Kagome Lattice Channel; Smooth Duct; Porous Media; Convective Heat Transfer; Pressure Losses
Date Published: January 12, 2026 DOI: 10.11159/jffhmt.2026.001
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