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Numerical Simulation and Analytical Modeling of Pulse Tube Refrigerators

Jafarian Dehkordi, Ali | 2009

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 39093 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan; Kazemzade Hannani, Siamak
  7. Abstract:
  8. First and second law analyses of the pulse tube refrigerator cycle are performed in the present thesis. In this respect, mass, momentum and energy balance equations are employed to derive the system of governing equations. Three models have been resulted depending on the employed theoretical model to analyze the pulse tube and thermal regenerator sections. In the first model, the tube section governing equations have been descritised and finite volume technique has been employed to solve the equations. In the regenerator a linear trend was assumed for the pressure and temperature to complete the solution procedure. To improve the regenerator model, harmonic approximation technique has been used to solve the regenerator governing equations analytically. The regenerator energy equations have been considered under local thermal equilibrium (LTEM) and dual energy equation model (DEEM) assumptions. In the second model, the linear regenerator assumption was released and harmonic solution proposed for the regenerator. Employing the second law of thermodynamics, the main sources of entropy generation have been studied and the second law of thermodynamic efficiency has been calculated. The third model has been reported in the present thesis, considering the descritised equations of the pulse tube and regenerator. Finite volume technique has been applied to achieve the numerical solution. In the above three mentioned models, the system of governing equations, in the form of one dimensional compressible oscillatory flow were solved to predict the cryocooler behavior. To investigate the two dimensional flow effects in the pulse tube, the related governing equations have been solved, employing harmonic approximation technique. Based on this model, complex Nusselt number and friction coefficient have been calculated analytically. Results showed that, among the three proposed models to analyze the pulse tube refrigerator, harmonic analysis of the regenerator and numerical solution of the descritised system of equations, led to the precise predictions for the cooling capacity
  9. Keywords:
  10. Pulse Tube Refrigrator ; Oscillating Flow ; Operability Index ; Regeneration Temperature ; Cooling Capacity

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