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Numerical and Experimental Investigation of Stator Grooves on Cooling of Generators

Erfanian Nakhchi Toosi, Mahdi | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50575 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nouri Borujerdi, Ali
  7. Abstract:
  8. The aim of this thesis is experimentally and numerically investigation of annular flow between the inner rotating smooth surface and the outer stationary grooved surface with or without axial fluid flow. Mounting grooves on the surfaces is important in cooling of rotating machineries such as electric generators and rotating heat pipes. The effect of different parameters such as the air gap between the surfaces, the geometry of the grooves, axial flow and rotation speed are numerically and experimentally investigated. The experimental results with axial grooves show that the entrance length decreases up to 17% with increasing the grooves depth. The reason is enhancement of the mixing and the perturbation of fluid flow inside the air gap. Heat transfer enhances up to 47% for . Increasing the Grashof number, increases the Nusselt number up to 2.2 of Nusselt number in stationary conditions. The results show that the heat transfer to pressure drop ratio is maximum for the case of and . The results show that with increasing the Reynolds number, the friction factor have similar trend with the friction factor of the air flow inside the pipes in the Moody chart due to similar behavior of the grooves with the surface roughness. The response surface methodology is used to obtain correlations for the pressure drop and the Nusselt number. Numerical investigation of turbulent flow in annular channels with rectangular and trapezoidal grooves with the opening angle of grooves in the range of by using (RNG) k– model is another part of this thesis. In this section, streamlines and isothermal lines are analyzed for different groove shapes. The numerical results show that the trapezoidal groove with increases the heat transfer up to 87% in comparison with the other groove shapes
  9. Keywords:
  10. Response Surface Methodology ; Entrance Region ; Pressure Drop ; Heat Transfer ; Annular Flow ; Annular Grooved Channel

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