Experimental investigation of heat transfer characteristics in a variable cross-sectioned two-pass channel with combined film cooling holes and inclined ribs

Heat transfer characteristics in variable cross-section two-pass channel with combined film cooling holes and ribs were studied experimentally. Rectangular ribs with an angle of 60° to the main flow roughened two opposite walls. The film cooling holes were distributed on the rib-roughened surfaces along the second pass. The relative roughness height was 0.123 and the relative roughness pitch was 12.5. The experiments were conducted under the Reynolds number range of 1.0 × 10⁴-6.0 × 10⁴. A series of experiments have been designed to explore how the exit mass flow rate effects on the heat transfer characteristics. Analysis of the experimental results may lead to the following conclusions, (1) with increasing the hole opening ratio, the heat transfer was enhanced while the exit mass flow rate keeping constant. (2) The flow resistance decreased with increasing the exit mass flow rate. (3) The relation between the exit mass flow rate and the Nusselt number was a quadratic function. (4) Different cooling hole locations produced different heat transfer effect.