Enhanced Heat Transfer Through Additively Manufactured Architectured Lattice Frame Materials in SS316L and Ti-6Al-4V

High porosity metal foams have been proven to yield high rates of heat dissipation. However, metal foams are available in limited configurations in terms of pore density and porosity as well as in limited materials, such as aluminum, copper etc. For the design and development of next generation high temperature heat exchangers, a significant increase in the heat transfer performance is required at a reasonable increase in pumping power, while at the same time, the materials should withstand the high temperatures as well as the mechanical loads. To this end, novel architectured materials with superior thermal performance as well as load bearing capabilities are designed and developed, with the support of state-of-the-art metal additive manufacturing. Three different unit cell topologies, viz. Tetrakaidecahedron (TKD), Rhombic-Dodecahedron (DDC) and Octet, are additively manufactured for porosities ranging between 0.7 and 0.9, in two materials Stainless Steel 316L and Ti-6Al-4V. Experiments have been conducted to determine the effective thermal conductivity and the convective heat transfer coefficient for the above samples with air as working fluid. The convective heat transfer experiments were carried out for air flow velocities ranging from 1–7 m/s through lattice frame samples which were one unit cell thick. The single unit cell configuration was designed to fully leverage the conjugate heat transfer capabilities where the struts are directly attached to the wall subjected to heat load. In general, the heat transfer for the lowest porosity samples of each topology was higher compared to the two higher porosity samples. The same is true for the pressure drop. For the highest porosity (0.9) samples, Octet performed marginally better than the TKD and DDC configurations for SS316L materials, while for the Ti-6Al-4V, the performance of the three unit cells were nearly similar for the 0.9 porosity. SS316L test articles exhibited higher convective heat transfer compared to the Ti-6Al-4V samples.