Multi-dimensional flow effects in pulse tube refrigerators

Pulse tube cryocoolers are often modeled as one-dimensional flow fields. We examine the adequacy of this assumption in this study. Two entire inertance tube pulse tube refrigerator (ITPTR) systems operating under a variety of thermal boundary conditions are modeled using a computational fluid dynamics (CFD) code. Each simulated ITPTRs includes a compressor, an after cooler, a regenerator, a pulse tube, cold and hot heat exchangers, an inertance tube, and a reservoir, and the simulations represent fully coupled systems operating in steady-periodic mode. The objectives are to ascertain the suitability of CFD methods for ITPTRs, and examine the extent of multi-dimensional flow effects in various ITPTR components. The results confirm that CFD simulations are capable of elucidating complex periodic processes in ITPTRs. The results also show that one-dimensional modeling is appropriate only when all the components in the system have large length-to-diameter (L/D) ratios. Significant multi-dimensional flow effects occur at the vicinity of component-to-component junctions, and secondary-flow recirculation patterns develop when one or more components have relatively small L/D ratios. Parameters in need of experimental measurement are discussed.