Experimental and numerical investigation of cooling effectiveness and heat transfer coefficient for straight and curved holes

The present study focuses on the experimental and numerical investigation of heat transfer performance downstream of the cooling holes on a flat plate with zero streamwise pressure gradient. The experiment was conducted in a low speed wind tunnel. The holes are circular in either straight or curved shape with an angle of 90°. In the experiments, both local and transverse averaged cooling effectiveness and heat transfer coefficient in the surface are studied for single and multiple holes in a row over a range of blowing ratio from 0.5 to 1.22 for single hole and 0.32-1.18 for multiple holes. Surface temperatures downstream of the injection were measured by means of thermal liquid crystals (TLC) and its associated camera system. Numerical simulation were perform for single hole at blowing ratios 0.51 and 1.04 by using Detached Eddy Simulation (DES) method based on S-A one equation turbulence model. In comparison with the straight hole, the curved one shows better overall performance expressed by net heat flux reduction (NHFR) based on both the experimental and numerical results, such as a better transverse spreading, higher cooling effectiveness and an increased local heat transfer coefficient are concluded for the curved hole.