Fusion Science and Technology / Volume 60 / Number 1 / July 2011 / Pages 228-232
Divertor & High Heat Flux Components / Proceedings of the Nineteenth Topical Meeting on the Technology of Fusion Energy (TOFE) (Part 1)
The helium-cooled plate-type divertor can reduce the number of divertor modules while accommodating heat fluxes q" up to 10 MW/m2 incident on tungsten-alloy armor. Dynamically similar experimental studies were performed to evaluate the thermal performance of variants of this divertor design at conditions that spanned the prototypical operating Reynolds number Re of 3.3 × 104. In the studies, a jet of air issuing from 0.5 mm and 2 mm wide slots impinged on and cooled a heated planar surface 2 mm away from the slot, then flowed through either a 2 mm wide channel or an array of cylindrical pin fins. The studies indicate that the fins, which increase the cooled surface area by a factor of 3.76, increase the effective heat transfer coefficient (HTC) by as much as 160% at a relatively modest increase in pressure drop of less than 40%.
These experimental results were used to determine the thermal performance of the actual plate design with helium cooling under prototypical conditions. Although the benefit of the fins is reduced because the fin efficiency decreases as the HTC increases, the predictions suggest that the fins could increase the maximum q" that can be accommodated by this design to ~18 MW/m2. Alternatively, for a given heat flux (e.g. 10 MW/m2), adding fins could allow operation of the divertor at lower coolant flow rates, and hence pumping powers.