Fusion Science and Technology / Volume 60 / Number 1 / July 2011 / Pages 190-196
Divertor & High Heat Flux Components / Proceedings of the Nineteenth Topical Meeting on the Technology of Fusion Energy (TOFE) (Part 1)
The addition of fins to the cooled surface of gas-cooled divertor modules has been proposed as a means to enhance their thermal performance, in the HEMP concept, for example. Such fins enhance heat transfer by significantly increasing the surface area over which convection occurs. However, adding fins also increases pressure losses and manufacturing costs and can adversely affect coolant flow over the cooled surface. More importantly, the high heat transfer coefficients expected with helium (He) cooling may significantly lower the fin efficiency, thereby limiting the extent of heat transfer enhancement to values well below the increase in the area ratio. An experimental investigation was undertaken to quantify the extent of heat transfer enhancement and corresponding pressure loss increase associated with the addition of pin fins to the cooled surface of a modular, helium-cooled, finger-type divertor. Four test cases, including configurations similar to the HEMP and HEMJ concepts, were studied. The results show that the addition of fins to helium jet-cooled finger divertors may not provide enough heat transfer enhancement to justify the associated increases in design complexity and pressure loss. Generalized charts for the thermal performance of helium-cooled divertors have been developed; these allow the designers to estimate the maximum allowable heat flux and corresponding pressure drop for a specified set of operating conditions and maximum operating temperature.