Experimental and numerical investigation of nozzle geometry effects on pressure drop in gyroid triply periodic minimal surface cores

Abstract

Compact heat exchangers with triply periodic minimal surface (TPMS) cores have emerged as a promising option for advanced thermal management; however, they typically exhibit high pressure drops, making it necessary to evaluate design aspects such as inlet nozzles to mitigate this penalty. This study addresses the gap regarding inlet-nozzle design for pressure-drop reduction by investigating whether and to what extent the inlet-nozzle geometry can reduce the pressure drop in TPMS cores at different porosity levels. To this end, three different nozzle geometries were proposed and evaluated across multiple porosity levels: a divergent nozzle, a conical nozzle, and a divergent–convergent nozzle that penetrates the core. Pressure drop was experimentally measured in additively manufactured polymer gyroid cores with porosities ranging from 0.33 to 0.42 for each nozzle geometry. Simulations were validated against experimental data for a porosity of 0.39, with a maximum deviation of 4.4%. Experiments demonstrated that pressure drop is inversely proportional to the porosity. The divergent nozzle presented the highest pressure drop at any porosity, while divergent–convergent nozzle yielded the lowest values. The maximum pressure-drop reduction from divergent to conical was 30.8% for 0.4 porosity, whereas the reduction from divergent to divergent–convergent reached 40% at 0.42 porosity. Simulation results indicated that the conical nozzle generates the lowest local pressure drop due to its flow-distribution pattern. Recirculation zones were observed in the inlet region due to geometric transitions and near the external walls. Overall, the results show that nozzle geometry is a critical design feature in TPMS heat exchangers; conical configurations can distribute the flow more effectively, reduce momentum variation, and increase local flow velocity in the inlet region.