Predictive capabilities in CFD simulations of additively manufactured extraction grid cooling channels for the DTT NBI system

Metal Additive Manufacturing (MAM) technology ena-bles the possibility of integrating the cooling system in ac-celerator components during the manufacturing process phase, obtaining extremely high density, and high thermal, and mechanical properties in metals. In the Neutral Beam Injector for the Divertor Tokamak Test facility, the beam acceleration components are submitted to extremely high-power loads and MAM represents a valid technology to manufacture the acceleration grids. One of the limitations of using such technology is the high surface roughness, which can affect the maximum admissible pressure drop for the design constraints of the cooling system. In this work, different single-channel samples have been additively manufactured and they have been tested by measuring pressure drop at different water flow rates. The single-channel samples have been internally smoothed via a chemical process to reduce the pressure drop and tested again. Computational Fluid Dynamics (CFD) models have been calibrated to properly predict the pressure drop of the single-channel samples. Based on this validation, the CFD models have been implemented to simulate the perfor-mance of the new Extraction Grid cooling system. The optimized shape of the EG cooling channels has been adopted to manufacture different scaled prototypes to reproduce the thermal power map, which is similar to the nominal one.