Performance and Reliability Improvements in a Low-Cost Stirling Cycle Cryocooler

Abstract

The use of a free piston, gas-bearing Stirling cycle cryocooler for commercial high temperature superconductor (HTS) applications dictates the cooler must not only be low cost, but also have long life and high reliability. Over the past two years Superconductor Technologies Inc. (STI) has integrated a new cryocooler design into our commercial HTS systems. This cooler is an improvement over the previous cooler we were using in this application however, further improvements were still attained with this new design, which presently has achieved a 1/COP of <17 w/w at 77K cold end temperature and 23°C ambient temperature. This paper will describe the performance, life, reliability and manufacturing cost improvements made to the cooler design over this time period. Data will be presented detailing the performance of the cooler over an ambient temperature range of 20°C to 70°C at various operating conditions. In addition to laboratory results, a Weibull analysis of life and reliability data from over 140 units in the field with a combined runtime of over 300,000 hours will be presented.