Experimental Investigation of Heat Transfer Dependency on Conjugate and Convective Thermal Boundary Conditions in Pin Fin Channel

Abstract

The present work experimentally quantifies the effects of thermal boundary conditions, i.e., conjugate and convective boundary conditions, on heat transfer performance for the pin fin channel in trailing edge of gas turbine blade. The geometry of pin fin arrays is typical of x/D=y/D=2.5 and H/D=1. For conjugate case, model is constructed with a relatively high conductivity material so that the Biot number of the model matches engine condition. Uniform heat flux is imposed along the external wall of pin fin arrays and highly resolved temperature distributions of internal wall is obtained with steady liquid crystal, meanwhile external temperature is measured through thermocouples. For convective case, model is constructed with low thermal conductivity material to ensure the usage of transient liquid crystal to obtain heat transfer coefficients of the internal wall on the same configuration. Both the measurements are used as boundary conditions to conduct simulation of solid part of pin fin array. Internal and external wall non-dimensional temperature distributions, as well as isothermal lines distribution, of the two cases are compared, results indicate that it will produce large errors in temperature predictions without considering conjugate effect. Further analysis are made about the mechanism of thermal boundary conditions in determining wall temperature, which demonstrates the necessity of taking conjugate heat transfer effect in turbine cooling design.