טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentRofman Baruch
SubjectInvestigation of a Compressible, Oscillating Flow and Heat
Transfer in a Stirling Cryocooler
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Emeritus Gershon Grossman
Full Thesis textFull thesis text - English Version


Abstract

Stirling Cryocoolers serve in a number of advanced technological applications to cool a variety of important components, such as infrared (IR) detectors, high temperature super conductors (HTSC), and cryogenic catheters. The Stirling Cryocooler and its derivative - the Pulse Tube cryocooler - operate in a periodic mode under which the working fluid (usually Helium) undergoes several stages of compression and expansion with simultaneous heat transfer. Understanding the behavior of the compressible, oscillating flow and the concomitant heat transfer is of the utmost importance to the design of these devices. Over the years, several studies have been preformed toward this objective, with a number of limiting simplifying assumptions.

In this work we have preformed a CFD (Computational Fluid Dynamics) solution for the flow and heat transfer in a two dimensional channel under the assumptions of laminar, oscillating flow. The compressible nature of the flow, (such as that of Helium), was taken into consideration. The governing equations of the problem were formulated and studied in their dimensionless form. A CFD model was created using Gambit and Fluent programs. The model had been validated by comparing it to the incompressible analytical solution. The compressibility effects were studied using the CFD solution. An analytical approximation of the compressible flow was formulated and examined.

The main conclusions were that the friction factors and the radial heat flux in the compressible flow are grater in comparison to their incompressible counter parts. The suggested explanation is that due to the pressure - temperature - density coupling the compressible flow is more energetic (can produce more power).