Forced convective heat transfer in square-ribbed coolant channels with helium gas for fusion power reactors

Square-ribbed coolant channels with helium gas for fusion power reactors were designed to enhance the turbulent heat transfer in comparison with smooth coolant channels. Heat transfer coefficients and friction factors in the square-ribbed annular channels were investigated quantitatively under high pressure. The turbulent heat transfer coefficients in the square-ribbed annulus, with a ratio of the rib pitch to a height of ten, were 200-300% higher than those in the smooth annulus and then the thermal-hydraulic empirical correlations were derived. The average heat fluxes from the heated wall were predicted using the present empirical correlations and the maximum heat flux at p/h = 10 reached x 1.5 MW/m(2) at Re = 65 000. From the results of the present study, it can be expected that the proposed rib-roughened coolant channels are available to remove surface heat fluxes at the first wall and blanket in the fusion power reactors. (C) 2000 Elsevier Science B.V. All rights reserved.