Phase shifting in pulse tube refrigerators

Different types of pulse tube refrigerators are described by alternative ph asor diagrams based on the volume flow rates applied at the ambient tempera ture inlets of the regenerator and of the pulse tube(s). This provides a si mple means for finding the optimum phase shift between pressure and flow ra te for PTRs operated with different kinds of phase shifters such as the ori fice system, the inertance tube, and the double inlet arrangement. The basi c features are discussed first for ideal systems with no losses. Then, thos e results are compared with experimental data of single- and two-stage puls e tube refrigerators and also with more comprehensive numerical calculation s which take account of irreversible losses caused by friction as well as h eat conduction and heat transfer. It is shown that for the pulse tube, the phase shift can be well estimated from the ideal model, whereas there is mo re discrepancy for the regenerator. Those phasor diagrams are shown to be h elpful tools for the design of multistage systems. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.