In the present study, a novel deflector system was proposed to improve the performance of a Savonius wind turbine through Computational Fluid Dynamics (CFD) simulation. For this purpose, an airfoil-shaped deflector was proposed and placed in front of the turbine to prevent the negative torque affecting the convex surface of the returning blade and also making it possible for deflecting the wind into the advancing blade. Different configurations of the proposed deflector system were considered numerically using the CFD solver. A three-dimensional incompressible unsteady Reynolds-averaged Navier-Stokes simulation in conjunction with the SST k − ω turbulence model was done and validated with the available experimental data. The predicted results indicated that the performance of the Savonius rotor is highly dependent on the position and angle of the deflector. Thus, there was an appropriate position and angle values to obtain the highest torque and power coefficients. It was concluded that using the favorable airfoil-shaped deflector significantly enhanced the static torque coefficient values in all angular ranges especially in the rotation angles between 0°-30° and 150°-180°. By properly covering the returning blade using the airfoil-shaped deflector, the static torque coefficient values increased up to two times higher than that generated by without deflector case.

No abstract

In the present study analytical solution for forced convection heat transfer in a circular duct with a special boundary condition has been presented, because the external wall temperature is a periodic function of axial direction. Local energy balance equation is written with reference to the fully developed regime. Also governing equations are two-dimensionally solved, and the effect of duct wall thickness has been considered. The temperature distribution of fluid and solid phases is assumed as a periodic function of axial direction and finally temperature distribution in the flow field, solid wall, and local Nusselt number, is obtained analytically.

No abstract

No abstract