Experimental study of heat transfer in snake-shaped variable cross-section channels with different ribs heights

The influence of the rib heights on heat transfer characteristics in U-shaped variable cross-section channels was experimentally studied in the steady state.The design parameters include:relative roughness pitch 15 mm,rib width 2 mm,and relative roughness heights 1 mm,1.5 mm,2 mm,and 2.5 mm,respectively,and Renault number from 12 000 to 56 000.Based on ribless channel of the same shape,the influence of rib heights on heat transfer effect and resistance of a channel with 15 mm pitch was studied,so an empirical relational expression comprising geometrical parameters was obtained.The experimental results show that,the heat transfer of ribbed channel will be improved;the influence of the rib heights on the heat transfer of U-shaped variable cross-section channel is not monotone,but distributed with multi peak values.The influence of rib heights on the resistance coefficient increases with the rib heights.