Prediction of local shear stress and heat transfer between internal rotating cylinder and longitudinal cavities on stationary cylinder with various shapes

A numerical analysis has been performed to simulate flow structure, heat transfer, and pressure drop of turbulent flow in an annulus with a few longitudinal cavities on the outer stationary cylinder. The cross sections of cavities are rectangular, closed and open trapezoidal shapes. This kind of annular flow is applicable to industries applications such as electrical generators where heat generates in the cavities containing wires, heating of axial compressor rotor drams, rotating heat pipes for cooling of superconducting machines or motor rotor. The governing equations of turbulent flow are solved by using Renormalization group (RNG) k–ε model for Reynolds and Taylor numbers in the range of 5×10 ³ <Re _a <6.5×10 ⁴ and 160<Ta<1900 respectively. The angle between the sides and the base of the trapezoid cavity is in the range of 70 ^∘ <β<135 ^∘ . The results show that the pressure drop is dependent on the cavity angle and reaches a maximum value at β=91 ^∘ , then declines. Furthermore, Sharp increase in heat transfer coefficient belongs to the corners of the cavity where are located in front of the fluid rotational flow. Furthermore, the averaged Nusselt number is dependent on both the effective Reynolds number and the aspect ratio but the Reynolds number is more effective. The present results are validated with available experimental data in the literature for rectangular cavities.