Pulse tube refrigerators are being increasingly favored for cryocooler industry applications because of their simplicity and the absence of moving parts at their low temperature regions. Therefore, numerical simulations of them are very essential. Most of proposed models used thermal equilibrium .Numerical simulation of an Inertance Tube Pulse Tube Refrigerator based on dual energy equation model in the regenerator as a porous media is proposed in the present thesis. In this model porous zone in the regenerator is simulated taking into account more realistic thermal condition, namely the non-equilibrium between the gas and solid matrix. Here, the focus is mainly on considering the influence of the two employed models, Local Thermal Equilibrium and Dual Energy Equation in the regenerator as a porous media on the predicted performance of an Inertance Tube Pulse Tube refrigerator .A detailed analysis of the flow and heat transfer under oscillating flow condition is performed using Computational Fluid Dynamic code. The simulation represents an ITPTR operating in the quasi-steady state condition. The results show that CFD simulation of the ITPTR is capable to model laminar oscillating flow through its components. To simulate this ITPTR several User Defined Functions are developed and hooked to FLUENT solver. The oscillating axis-symmetric flow and temperature fields in various components of ITPTR are computed by solving the full set of conservation equations. The working fluid in this system is helium. . Here, geometric characteristic of the studied ITPTR are the same as experimental Orifice Pulse Tube Refrigerator rig, used in Georgia Institute of Technology.except employing an inertance tube instead of orifice valve. The results of this simulation are in good agreement with experimental data. The solution of equation is accomplished with the help of User Defined Scalars defined for porous zone in regenerator. The results confirmed that the DEE model is more accurate than LTE model. Temperature profile in regenerator, mean temperature in Cold Heat Exchanger and cyclic heat transfer of CHX in DEE model are closer to the experimental data than that of the LTE model. An analysis of regenerator based on second law of thermodynamics is carried out. This analysis shows that the most entropy generation and energy loses are exited in hot head of regenerator. To solve this problem a study of multi segments regenerator with different mesh configurations is performed. The results confirmed that the multi segment regenerator with higher porosity mesh at the hot head of regenerator can improve regenerator efficiency. Key words: Pulse Tube, Regenerator, Non-Thermal equilibrium, Multi Mesh