Optimization of Pin-fin Arrays for Helium-cooled Finger-type Divertor

The helium-cooled modular divertor concept with integrated pin array developed by the Karlsruhe Research Center (FZK) is unusual among helium-cooled tungsten divertor designs in that it relies upon an array of pin fins on the back of the cooled surface, instead of jet impingement, to cool the plasma-facing surface. The Georgia Tech group experimentally studied a similar design constructed of brass which combined jet impingement with an array of identical cylindrical pin fins using air at nondimensional coolant mass flow rates, i.e. Reynolds numbers, which spanned the range expected under prototypical conditions. The results suggested that the pin-fin array, at least for the particular geometry studied, provides little, if any, additional cooling beyond that provided by jet impingement. Given that this earlier study considered only one pinfin array geometry, however, a numerical study was performed to investigate whether changes in the array geometry could improve performance. Specifically, numerical simulations using the commercially available computational fluid dynamics software package ANSYS 14.0 was used to examine how varying the pitch-todiameter ratio for the fin array and the aspect ratio of the fins affected average pressure boundary temperature and the pressure drop across the divertor. These results can, with appropriate experimental validation, be used to determine whether pin-fin arrays can be used to improve the thermal performance of a variety of helium-cooled tungsten divertors.