Abstract: This study focuses on the numerical simulation of heat transfer and fluid flow within a cooling channel equipped with V-IV ribs. The dimensions of the cooling channel are consistent with those used in experimental investigations to ensure comparability of results. Simulations were conducted using the commercial software STAR CCM+ 2019, modeling three-dimensional, turbulent gas flow under implicit unsteady conditions with wall Y+ considerations. A no-slip velocity condition was enforced at the walls, with a turbulent velocity profile specified at the inlet and a pressure outlet condition at the outlet, maintaining an ambient temperature of 300 K. The Large Eddy Simulation (LES) technique was employed, utilizing high-performance computing resources to achieve timely results. The Wall-Adapting Local Eddy-viscosity (WALE) model was implemented for subgrid-scale turbulence modeling, with first-order temporal discretization and a time step size of 0.0001 seconds. A grid independence study was performed at a Reynolds number of 70,000, using trimmer and surface mesh techniques for mesh generation. Four mesh densities were tested: 2.3 million, 5.6 million, and 8.6 million cells, resulting in Nusselt numbers of 207.68, 228.83, and 228.24, respectively. The 5.6 million cell mesh provided results closely matching the finer mesh configurations and was thus selected for further simulations. The wall Y+ values were analyzed to ensure the effective use of prism layers near the walls, maintaining values below one to resolve the viscous sublayer accurately. Twelve prism layers with a stretching factor of 1.2 were utilized. The velocity distributions were examined for three cases, revealing that the V-IV ribs create secondary flows and recirculation zones, particularly in and after the bend region. This disruption leads to increased turbulence, which is consistently observed across all cases. The study highlights the complex interactions between airflow and rib structures, providing insights into optimizing cooling channel designs for improved heat transfer and fluid flow characteristics.KEYWORDS: Turbulence Modeling, Ribs, Heat Transfer Enhancement, LES, Gas Turbine cooling

The current research was carried out to investigate conventional heat transfer enhancement inside the tube by using twisted stainless-steel angle insert. Main objectives were to find the percentage of increment of heat transfer enhancement using twisted stainless-steel insert and to find the relation between Reynolds number and Nusselt number. A 940mm long copper tube of 26.6 mm internal diameter and 30 mm outer diameter, of which length of 762 mm has been used as the test section. A constant heat flux condition has been maintained by wrapping Nichrome wire around the test section and fiber glass insulation over the wire. K-type thermocouples and rotameter were used to measure temperature and rate of flow. With insert, heat transfer rate has been increased up to 140 percent. This technique does not rely on external power or activation. This experiment has shown simultaneous effects on Reynolds number and Nusselt number too.