A simple method for the analysis of sub-Kelvin refrigerators that use a dilute superfluid 3He–4He mixture as a working fluid Original Research Article

The recent development of new types of sub-Kelvin refrigerators that use dilute superfluid 3He–4He mixtures has made it apparent that a simple method of cycle analysis is needed. General control volume forms of the first and second laws of thermodynamics appropriate to this working fluid are presented. Simple analytic constitutive relations for the internal energy, entropy, enthalpy, osmotic enthalpy and 4He chemical potential are presented. Several examples are worked out using these relations.