Effect of hole shape on the heat transfer in a rectangular duct with perforated blockage walls

Heat transfer coefficients were measured by the improved hue detection based liquid crystal technique in a turbine blade internal cooling passage model with blockage walls. In the experiments, blockages with 9 holes of circular, wide, narrow shapes were used and for the circular shape, the number of hole of 7, 9, and I I were tested. For all cases, the perforated area was kept same. Results showed that the staggered impingement jets increased heat transfer coefficient, however. pressure drop also increased greatly. Generally, Nusselt number ratio and the thermal performance factor decreased as Reynolds number increased. For all Reynolds numbers tested, the blockage wall with wide holes gave more uniform heat transfer coefficient and higher thermal performance factor. As the number of hole increased from 7 to 11, the distribution of heat transfer coefficient became Uniform and the thermal performance factor increased.