Numerical Simulations of fluid flow and heat transfer in pulse tubes

Pulse tube refrigerators give rise to many loss mechanisms, particularly within the pulse tube component, which greatly affect their overall thermodynamic efficiency. These losses are not well understood, as a comprehensive model that can take into account the effect of such loss mechanisms does not currently exist. In addition, the difficulty of obtaining accurate experimental data has contributed to this lack of understanding. In this paper, a comprehensive model is developed which simulates the flow process and heat transfer within the pulse tube component of orifice pulse tube refrigerators. In the model, the fluid oscillations are simulated using two dynamic meshes that move periodically and have a specified phase difference. The model includes the pulse tube and cold and warm end heat exchangers at the end of the pulse tube. Simulation results for the dynamic evolution of the temperature and velocity profiles along the tube axis are presented for several case studies. The simulations indicate the formation of a wall jet near the tube wall, in agreement with experimental observations. They also confirm the existence of momentum streaming, as well as radial heat conduction losses to the pulse tube wall. The thermodynamic performance of the tube is also quantified and compared with the available experimental data.