Chapter 42 - Future trend of pulse tube cryocooler research

Abstract

One of the important subjects for the future progress of flexible pulse tube coolers is a substantial improvement of the software as a design tool of the cryocooler, which could be used to the actual application. Several proposals based on a basic cycle analysis are presented in this chapter. The flexibility of a pulse tube allows integrating the cryocooler with its application. However, the drawback will be a deterioration of thermodynamic efficiency because of the application oriented design philosophy. There are many analytical methods of pulse tube coolers. Some of them are precise analysis of a particular component; such as a regenerator, a pulse tube phase shifter and others are the simplified analysis of total system. Most of them, however, are not easy to use it extensively for the new users. In other words, the developed numerical codes are generally not easy to understand. To keep the thermodynamic efficiency high enough for the applications, several approaches have been described based on the simplified computer analysis. For valved type pulse tube coolers, the operating condition to minimize the valve loss is given. The use of resonant displacer as a phase shifter for valve-less pulse tube cooler gives Carnot efficiency as its maximum efficiency. Possibility of such a phase shift mechanism without use of an orifice and a reservoir is introduced by a simplified calculation.