Convective heat transfer characteristics of sparse hole wall in semi-closed narrow channel
In order to study the convective heat transfer characteristics inside the double-wall composite cooling turbine blade,a narrow semi-closed passage with lateral outflow through sparse holes was designed.Test methods were used to study the effects of different inlet Reynolds numbers and geometric parameters of outflow holes on the convective heat transfer characteristics of the outflow wall surface.The results showed that,the superposition of overflow effect and impact effect occurred in the downstream area of the outlet hole due to the outflow of cool air.A typical droplet cryogenic zone appeared in the downstream area of the outlet hole,and its coverage area increased with the increase of the outlet hole size and inlet Re number;the average Nusselt number of the outlet wall presented four variation characteristics along the flow direction.The average Nusselt number of the inlet section was 80％higher than that of the downstream section;there was an optimal outlet hole span spacing ratio,so that the average convective heat transfer coefficient on the wall reached the maximum.The average wall Nusselt number of the major hole spacing was 20％lower than that of the intermediate hole spacing.
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