Free-Piston Stirling Cooler for Electronics Cooling in High Temperature Environments

This paper discusses active cooling devices used to maintain acceptable temperature levels for electronics packages in a high temperature environment. The temperature control is provided by a free-piston Stirling cooler (FPSC). The FPSC is a compact, quiet, low-vibration, environmentally benign cooling device based on the Stirling cycle. In principle, the cold side temperature of the FPSC, that thermally regulates the electronics package, is controllable from a low end, at cryogenic temperatures, upwards to the hot side temperature, which is limited only to the maximum temperature survivable by the materials used to construct the driving motor. General characteristics of the FPSC are discussed from the standpoint of electronics cooling and various options for heat transport are presented. Two prototype FPSCs have been developed for cooling electronics packages in applications where it has not been possible to accomplish even close to the requirements with existing technology. The first prototype is being used to cool an electronics package to below 100°C in a 200°C operating environment. The hot side temperature of the FPSC was designed to operate at 230°C in order to reject heat to the 200°C ambient, while limiting the motor temperature to less than 250°C. A cooling capacity of 120 W was achieved. The second prototype is used to provide conditioned air for a sealed, waterproof, electronics enclosure that is exposed to a 60°C environment. The FPSC operating temperatures for this application are 30°C on the cold side and 80°C on the hot side, with a cooling capacity of 500 W.