COMPARISON OF 1D AND 2D FLOW NUMERICAL ANALYSIS APPLIED TO TWO STAGE PULSE TUBE CRYOCOOLER

In the recent years, for several applications such as cooling of sensors, super conducting magnets, cryo-pumping etc., there are worldwide efforts to replace cooling with liquid helium by cooling with closed cycle cryocoolers. The internal working processes in pulse tube cryocoolers are quite complex due to unsteady, oscillating compressible gas flow in the pulse tube. Although considerable theoretical studies have been carried out phenomena occurring in pulse tubes are still to be understood. Three different numerical models namely isothermal model, adiabatic model and energy equation model based on the assumption of one-dimensional flow are compared with a Computational Fluid Dynamics (CFD) model based on a two dimensional flow approach to analyze a two stage pulse tube cryocooler. The various experimental parameters have been incorporated in the models to carry out the analysis. The various losses of the pulse tube cryocooler are calculated separately and incorporated into the 1D models. CFD analysis is carried out without any assumptions except the helium is treated as ideal gas. The numerical results are compared with the experimental results obtained for a two stage pulse tube cryocooler for validation.