Parasitic heat load in a miniature pulse tube cooler

Abstract

The parasitic heat load represents the heat flow disturbing the cold end of cryocoolers due to conduction, convection and radiation. On-board space missions, cryocoolers such as pulse tubes are typically employed in a cold redundancy scheme. Therefore, the heat flow through a pulse tube cooler in OFF state directly affects the cold performance of the operating cooler, bringing in heat and limiting the total available cooling power at the cold tip. The reference pulse tube is a miniature pulse tube cooler, developed for 2 W cooling at 80 K with a low input power. This study aims first to measure the parasitic heat load through three methods, which results are compared and confronted with numerical evaluation based on well-known correlations. Then a novel way in design is proposed, integrating an element of lower conduction replacing a part of the regenerator in order to reduce the heat load. The impact of this modification on the performance is measured and compared with its influence on the heat load.