DETAILED MEASUREMENTS OF HEAT TRANSFER ON AND AROUND A PEDESTAL IN FULLY DEVELOPED PASSAGE FLOW.

Many advanced gas turbines use sophisticated internal cooling passages to limit turbine blade temperatures. Within such passages pedestals (transverse cylinders) are frequently employed to increase heat transfer to the cooling air. This paper is concerned with the heat transfer enhancement associated with a pedestal situated in fully developed passage flow. Results of measured local heat transfer coefficient both on the cylinder itself and on the passage wall adjacent to the cylinder are presented. The experimental technique employed is a transient method which makes use of thermochromic liquid crystals to furnish a complete map of heat transfer coefficient. The current work has investigated the variation of these heat transfer distributions with both cylinder length to diameter ratio and Reynolds number. In addition a flow visualisation study has been conducted to determine the complex secondary flows developed around the cylinder. The relationship between heat transfer enhancement and the flow field is then discussed