Thermohydraulics of rib-roughened helium gas running cooling channels for first wall applications

Abstract

Improved cooling channel designs of helium cooled first wall (FW) applications focus on efficient heat transfer enhancement and reduced material temperatures, even for high incident heat flux densities of more than 0.5MW/m2. To this end, thermohydraulics of turbulent flow in a one-sided heated, one-sided rib-roughened channel with squared, round-edged cross section were predicted by Detached Eddy Simulations (DES) at Reynolds numbers ranging from ReDh=1.0E4 to ReDh=1.5E5 and at heat up rates ranging from q+=1.1E−3 to q+=7.48E−4, encompassing the envisaged operation envelope of helium cooled FW cooling channels. The rib-roughened channel wall consists of centrally positioned, transversally oriented rib elements with a rib-pitch-to-rib-height-ratio of p/e=10, a rib-height-to-hydraulic-diameter-ratio of e/Dh=0.0638 and a rib-width-to-channel-width-ratio of l/W=0.6. Mean flow and heat transfer quantities, turbulent fluxes and flow structures were analyzed. Anisotropic, large-scale eddies originated in separated shear layers are shed vertically and laterally to the flow. Maximum heat transfer correlates with regions of maximum span- and crosswise turbulent fluctuations and is located at the rib leading edge. Minimum heat transfer occurs within the region of the counter-rotating vortex behind the rib.