Analysis of streaming effects in stirling-type inertance pulse tube cryocoolers using computational fluid dynamics

To look inside a pulse tube for streaming effects beyond 5–6 Hz is not possible experimentally. Therefore, CFD is a reliable tool for observing the streaming effects occurring in a cryocooler. In the present work, a numerical investigation on the inertance type pulse tube cryocooler (IPTCC) is carried out using computational fluid dynamics (CFD) at frequencies greater than 80 Hz. A numerical model is developed, and simulations are validated against the numerical results published in the open literature. As opposed to the local thermal non-equilibrium model, porous media are modelled using a local thermal equilibrium approach. The streaming effects are analysed in the pulse tube for various sizes and frequencies with temperature-dependent material properties. It was observed that Rayleigh streaming is most likely to occur when the viscous penetration depth is very small compared to the pulse tube radius. Further, it was also examined that streaming is purely acoustical, not due to the transition to turbulent flow in the pulse tube. While varying the whole length of IPTCC, Rayleigh streaming occurred at a particular combination of size and frequency. Furthermore, the streaming at different time periods was analysed for two cases of different IPTCC lengths. It was found that a combination of various factors and flow conditions resulted in the appearance and disappearance of vortices in the pulse tube in various instances. The present study also suggests an interplay between the acoustic power density, size, and frequency of the IPTCC. It is concluded that CFD modelling is necessary to observe the multidimensional effects and complex transport phenomena in IPTCC.