ISOTHERMAL MODEL OF PULSE TUBE REFRIGERATOR

The isothermal model is very useful for analysis of Stirling refrigera tors because of its simplicity, but to date it has not been applied to pulse tube refrigerators. In this paper, an isothermal model for puls e tube refrigerators is introduced. This model is based on the premise that a pulse tube refrigerator can be considered to be a type of spli t Stirling refrigerator, and the gas in the pulse tube can be divided into three parts. The main assumptions of the isothermal model are tha t the gas in the middle part of the pulse tube is adiabatic and the ga s in the other parts is isothermal. Though the present isothermal mode l is more complex than the isothermal model for the Stirling refrigera tor, it is much simpler than a nodal analysis. The results from the is othermal model are compared with those of the nodal analysis. The gros s refrigeration power and the input power using the former are almost- equal-to 20% lower than values obtained using the latter. The pressure ratio and the average mass flow rate are almost-equal-to 5% lower usi ng the isothermal model.