General pulse tube theory

A brief review of pulse tube thermodynamics is given. The underlying phenomena are described starting with a very simplified model. The concept of phasor analysis is used to show the fundamental behaviour. The concept of enthalpy flow is expanded to include entropy and Gibbs free energy flows and to apply these for the first time to regenerative refrigerators. A simplified model based on enthalpy, entropy and Gibbs free energy flows is presented to illustrate the effects of temperature gradients, thermal conduction and viscosity. As models become more sophisticated, more features are included. Furthermore, it is shown that, contrary to common usage, the concepts of work, flow and heat flow are not useful when applied to regenerative refrigerators. Rather, the Gibbs free energy flow fulfils the role usually assigned to work and heat flows. Recent advances in thermoacoustic and 2-D flow models are also reviewed.