The turbulent flow between coaxial cylinders, particularly when the inner cylinder is rotating, exhibits complex hydrodynamic and heat transfer behaviors critical for various engineering applications. While many previous studies have simplified these systems with idealized assumptions, real-world scenarios involve mixed convection and turbulence, making accurate predictions more challenging. This study numerically explores the hydrodynamic and thermal characteristics of turbulent flow within coaxial cylinders, considering different rotational and axial flow conditions. The investigation utilizes three turbulence models, namely k-ε, SST k-ω, and k-ω, to assess the effects of rotational speed and axial velocity on flow dynamics and heat transfer. The outer cylinder remains stationary as the inner cylinder rotates, and a steady flow of heat is directed onto the outer surface. The results show that increasing rotational and axial velocities enhances turbulence, significantly improving heat transfer. The coefficient of skin friction decreases by 35% from the inlet to the outlet. Additionally, doubling the angular velocity increases the friction coefficient by a factor of 5, while a fivefold increase boosts it by 16 times. These findings provide important insights for optimizing the design of heat exchangers, industrial mixing systems, and chemical reactors, where effective control of turbulent flow is crucial.
