1 Copyright © 2017 by ASME 0+Proceedings of ASME Turbo Expo 2017: Turbine Technical Conference and Exposition GT2017 June 26-30, 2017, Charlotte, NC USA GT2017-64982 HEAT TRANSFER ANALYSIS OF THE SURFACE OF NONFILM-COOLED AND FILM- COOLED NOZZLE GUIDE VANES IN TRANSONIC ANNULAR CASCADE Kasem E. Ragab Mechanical Engineering Department The American University in Cairo New Cairo, Egypt Lamyaa El-Gabry Mechanical Engineering Department The American University in Cairo New Cairo, Egypt ABSTRACT One of the approaches adopted to improve turbine efficiency and increase power to weight ratio is reducing vane count. In the current study, numerical analysis was performed for the heat transfer over the surface of nozzle guide vanes under the condition of reduced vane count using three dimensional computational fluid dynamics (CFD) models. The investigation has taken place in two stages: the baseline nonfilm-cooled nozzle guide vane, and the film-cooled nozzle guide vane. A finite volume based commercial code (ANSYS CFX 15) was used to build and analyze the CFD models. The investigated annular cascade has no heat transfer measurements available; hence in order to validate the CFD models against experimental data, two standalone studies were carried out on the NASA C3X vanes, one on the nonfilm-cooled C3X vane and the other on the film-cooled C3X vane. Different modelling parameters were investigated including turbulence models in order to obtain good agreement with the C3X experimental data, the same parameters were used afterwards to model the industrial nozzle guide vanes. Three Shear Stress Transport (SST) turbulence model variations were evaluated, the SST with Gamma-Theta transition model was found to yield the best agreement with the experimental results; model capabilities were demonstrated when the laminar to turbulent transition took place NOMENCLATURE C Chord length [mm] Cp Specific heat at constant pressure [J K -1 kg -1 ] Cr Nusselt number correction factor HTC Heat Transfer Coefficient [W m -2 K -1 ] κ Thermal conductivity [W m -1 K -1 )] k Specific heat ratio [-] k Kinetic energy [J kg -1 ] M Mach number [-] ̇ Mass Flow Rate [g s -1 ] p Pressure [kPa] ρ Density [kg m -3 ] Re Reynolds number   Momentum thickness Reynolds number T Temperature [K] Tu Turbulence intensity  + Dimensionless wall distance (   )  Dissipation rate  Intermittency  Normalized wall temperature  Dynamic viscosity [N s m -2 ]  Specific dissipation rate Subscripts and Abbreviations ASC Annular Sector Cascade BL Boundary Layer CC Curvature Correction CFD Computational Fluid Dynamics KTH Kungliga Tekniska Högskolan (in Swedish) LE Leading Edge N/A Not Applicable NGV Nozzle Guide Vane PS Pressure Side RANS Reynolds Averaged Navier Stokes SGT Siemens Gas Turbine SST Shear Stress Transport SS Suction Side TE Trailing Edge VKI Von Karman Institute 1 Inlet value 2 Exit value a adiabatic D Diameter exit Value at the vane exit g Gas hub Hub m mainstream mid Midspan r recovery s Static t Total turb Turbulence w Wall x Axial reference INTRODUCTION Gas turbines have aroused interest of researchers and technology developers over the last decades since they eliminate several problems associated with other types of engines, for instance, the balancing problems are reduced due to the absence of reciprocating and rubbing elements. Increasing the temperature of hot gases entering the turbine improves the overall turbine efficiency as well as the ratio of the positive turbine work to the negative compressor work,