Flow and heat transfer characteristics of supercritical hydrogen in unilateral heated channels with micro-ribs

Micro-rib is an effective method for heat transfer regulation in scramjet regenerative cooling channels. The coolant properties have remarkable influence on the cooling performance. In order to investigate heat transfer characteristics of supercritical hydrogen flow in the micro-ribbed cooling channel, developments of fluid boundary layers are illustrated and parametric studies of micro-rib height are conducted. Results indicate that micro-ribs cannot always effectively reduce wall temperature for supercritical hydrogen due to abnormally thickened thermal boundary layer. Under severe thermal stratification, thermal boundary layer thickness can be up to 1/3 of channel height and significantly thicker than velocity boundary layer. Only when fluid thermal diffusion of supercritical hydrogen in channel center is promoted, heat transfer will be locally enhanced. Under given conditions, heat transfer deterioration of supercritical hydrogen occurs at 4, 5 MW/m². Under deteriorated heat transfer at 5 MW/m², micro-ribs with h/H = 10 % could enhance local heat transfer in the channel.