Computational fluid dynamics Study with heat transfer inside the embedded cooling channels for prototype ion extractor grid-1 and comparison with experimental results

Abstract

This study examines Computational Fluid Dynamics (CFD) with heat transfer analysis in the embedded semi-circular wavy mini cooling channels of the Steady State Superconducting Tokamak-1 (SST-1) Neutral Beam Injection (NBI) Prototype Ion Extractor Grid-1. A detailed analysis is conducted to assess heat transfer performance during long pulse operation by validating the numerical simulations for the experimental results. A prototype ion extractor grid of size 150 mm × 60 mm (say PG-1) is fabricated with 4 Computer Numerical Control (CNC) milled semi-circular wavy water mini cooling channels (R 1.1 ± 0.05 mm) on Oxygen Free Electronic (OFE) copper base plate for SST-1 NBI system as a part of in-house technology development. These cooling channels are covered by the copper electro-deposition technique. This PG-1 consists of 19 apertures, each of diameter 8 mm. The present work described CFD with heat transfer analysis of PG-1 using the ANSYS Fluent code. The analysis was performed by considering the Shear Stress Transport (SST) k-ꞷ turbulence model to simulate the present computational fluid domain. This analysis would help to understand the thermal and fluid dynamic behaviours of the grid when subjected to thermal loads. The flow analysis focuses on key parameters such as surface temperature distribution, water velocity distribution, and water flow patterns inside the mini cooling channels of the grid along with the water-to-copper surface interface temperature. The flow analysis considered the following boundary conditions: absorbed heat load of 5.49 kW, water mass flow rate of 0.078 kg/s, and inlet water temperature of 26 °C. The flow analysis results reveal that the maximum surface temperature of OFE copper is 122.32 °C, while the average surface temperature is 82.80 °C. The maximum surface-to-water interface temperature is 75.92 °C. The average water velocity within the channels is observed as 10 m/s. The flow simulated results are also compared with the High Heat Flux Test results and found moderate agreement within a maximum surface temperature deviation of ∼ 20 %.