Author : Rajesh V R and Biju T Kuzhiveli

The Stirling cycle cooler is a free piston linear motor driven device. The cooling technology using reversed Stirling cycle offers an outstanding opportunity to provide a compact, environment friendly system with comparable energy consumption. Analysis of Stirling cryocoolers has been an important research area for the past many years. This cooler operates as a closed regenerative cycle: closed because there are no valves, a fixed mass of working fluid (usually helium) being repeatedly circulated through the same thermodynamic processes; and it’s called as a regenerative cycle as the key component is the thermal regenerator. The linear motor can be considered as the heart of the entire cooler. It drives the compressor piston (or power piston), which compresses the working fluid alternately. In the present work, moving magnet concept has been employed in contrast to the conventional moving coil type motor. This innovative idea avoids the requirements of oscillating electrical connections and reduces the risk of contamination of the working fluid. The permanent magnet material and magnetization, coil gage size and the materials for the inner and outer yoke are important from the point of view of motor performance and cost. The influence of different geometric and electromagnetic parameters on the performance of the motor is analyzed in this paper. For the analysis of each configuration, the relation between the magnet height under the influence of magnetic field and piston amplitude is established mathematically. The periodic variation of active magnet height in the magnetic field has been analyzed electromagnetically and the relations among the parameters are determined.

Keywords: Stirling cooler, linear motor, moving magnet.

Article published in International Conference on Advances in Mechanical Sciences 2014, Special Issue-2 (Feb 2014)