Analysis of Heat Transfer Phenomena on High Response Heat Insulation Coatings by Instantaneous Heat Flux Measurement and Boundary Layer Visualization

Coating the heat insulation materials on the combustion chamber walls is one of the solutions to reduce the cooling loss of internal combustion engines. In order to examine the coatings, the evaluation of the heat transfer coefficient and the analysis of the heat transfer phenomena on the heat insulated walls are important. Firstly, the highly-responsive wall temperature sensor is developed, and the instantaneous wall heat flux is measured to evaluate the heat transfer coefficient on the heat insulated walls. The results show that the Nusselt number on the heat insulated walls is less influenced by the Reynolds number variation than that on the metal walls. Secondly, the high speed µ-PIV is employed to analyze the various turbulent flow characteristics. The results show that the turbulent dissipation on the heat insulated walls is smaller than that on the metal walls.