Construction of a Heat Transfer Rig based on Energy Balance for Rapid Production of Correlations for Additively Manufactured Geometries

Sammanfattning: This thesis has set the first milestones towards building a Nusselt number correlation that adapts to the current state of art designing and manufacturing processes at Siemens Industrial Turbomachinery AB, focusing on cooling mini-channels produced with Additive Manufacturing.  Additive manufacturing (AM), also known as 3D printing, is a gamechanger technology that has revolutionised manufacture and design know-how, bringing down production cost, time and waste. There are techniques within AM that can be applied in the gas turbine industry. Particularly, Selective Laser Melting (SLM) can be utilised to build high-temperature-alloy components without the design constraints imposed by conventional manufacturing. However, when assessing the performance of these AM components, challenges arise due to surface roughness inherent to the SLM process. The goal is to assess SLM parts for a specific application: thermal performance of AM cooling minichannels. This thesis presents the design, construction and validation of a heat transfer experimental rig, capable of assessing the Nusselt number in SLM single mini-channel samples. The SLM samples vary in the material alloy used for its fabrication, the shape of the mini-channel, and hydraulic diameter. The results show that SLM channels have a higher Nusselt number than smooth, conventionally manufactured channels. This heat transfer enhancement comes at a cost: an increased friction factor coefficient, which was the subject of study in a parallel thesis conducted in the same facilities. The relative friction growth of an SLM sample is significantly higher than the increase in relative Nusselt number for the same SLM when compared to the smooth channel performance. These results are aligned with the expectations, matching the general trends observed in the literature. However, some contradictions with other studies were obtained: surface roughness, the key factor affecting flow performance, yielded inconclusive effects for the results obtained in the present thesis. Further assessment and validation of the heat transfer rig built is to be pursued.