CFD analysis of nonlinear processes in pulse tube refrigerators: Streaming induced by vortices

Streaming in the pulse tube refrigerator is a crucial nonlinear flow and heat transfer phenomenon which considerably affects the refrigeration temperature and performance. The third type streaming in the pulse tube refrigerator is studied using computational fluid dynamics method for the first time. A two-dimensional simulation of an inline inertance tube pulse tube refrigerator (ITPTR) is performed for different operating frequencies with the help of the FLUENT® package. The streaming is found to be formed due to the generation, evolution and shedding of vortices and pressure drops which are induced by the hydrodynamic and thermodynamic asymmetries along the refrigeration system. The pressure drops due to abrupt changes of the tube cross sections at both hot and cold ends in the pulse tube are calculated and the mass flow rate of the streaming is predicted. The geometry, temperature gradient and especially frequency are revealed as the main factors influencing the streaming patterns and final refrigeration performance. The numerical results agree well with the substantial experiments and indicate further suppression and optimization methods.