شبيه سازي يك سرد ساز ضرباني و بررسي پارامترهاي موثر برعملكرد آن

چكيده انگليسي :

A Numerical Simulation of a Pulse Tube and Analysis of Effective Parameters on its Performance Bahador Mousavi b moosavi@me iut ac ir May 10 th 2010 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Ali Akbar Alemrajabi Rajabi@cc iut ac irAbstractPulse tube refrigerators PTR are being increasingly favored for cryocooler industry applications because of theirsimplicity and the absence of moving parts at their low temperature regions Therefore numerical simulations ofthem are very essential Most of proposed models used thermal equilibrium assumption for porous zones regenerator and heat exchangers Numerical simulation of an Inertance Tube Pulse Tube Refrigerator ITPTR based on dual energy equation model in the regenerator as a porous media is proposed in the present thesis In thismodel porous zone in the regenerator is simulated taking into account more realistic thermal condition namely thenon equilibrium between the gas and solid matrix Here the focus is mainly on considering the influence of the twoemployed models Local Thermal Equilibrium LTE and Dual Energy Equation DEE in the regenerator as aporous media on the predicted performance of an Inertance Tube Pulse Tube refrigerator ITPTR A detailedanalysis of the flow and heat transfer under oscillating flow condition is performed using Computational FluidDynamic CFD code The simulation represents an ITPTR operating in the quasi steady state condition The resultsshow that CFD simulation of the ITPTR is capable to model laminar oscillating flow through its components Tosimulate this ITPTR several User Defined Functions UDF are developed and hooked to FLUENT solver Theoscillating axis symmetric flow and temperature fields in various components of ITPTR are computed by solvingthe full set of conservation equations The working fluid in this system is helium In this simulation helium isassumed as an ideal gas and the viscosity of the working fluid is varying with temperature Here geometriccharacteristic of the studied ITPTR are the same as experimental Orifice Pulse Tube Refrigerator OPTR rig usedin Georgia Institute of Technology GIT except employing an inertance tube instead of orifice valve inertancetubes are used to control the phase shift between mass flow and pressure to improve the performance of thesecoolers The results of this simulation are in good agreement with experimental data Dynamic meshing is used tocreate deforming mesh used to model compression and expansion processes in the compressor in which the volumeof the domain changes with time A UDF is developed for creating the motion of the compressor piston Thesolution of equation is accomplished with the help of User Defined Scalars UDS defined for porous zone inregenerator The results confirmed that the DEE model is more accurate than LTE model Temperature profile inregenerator mean temperature in Cold Heat Exchanger CHX and cyclic heat transfer of CHX in DEE model arecloser to the experimental data than that of the LTE model An analysis of regenerator based on second law ofthermodynamics is carried out This analysis shows that the most entropy generation and energy loses are exited inhot head of regenerator To solve this problem a study of multi segments regenerator with different meshconfigurations is performed The results confirmed that the multi segment regenerator with higher porosity mesh atthe hot head of regenerator can improve regenerator efficiency Key wordsPulse Tube Regenerator Non Thermal equilibrium Multi Mesh

موسوي، بهادر

شبيه سازي يك سرد ساز ضرباني و بررسي پارامترهاي موثر برعملكرد آن

محيط متخلخل , بازياب , عدم تعادل حرارتي فاز جامد و سيال , بازياب يامش مركب