Sizing and Dynamic Performance Prediction Tools for 20 K Hydrogen Sorption Cryocoolers

Abstract

Two continuous operation 18 K/20 K sorption coolers are being developed by the Jet Propulsion Laboratory (JPL) as a NASA contribution to the European Space Agency (ESA) Planck mission that is currently planned for a 2007 launch. The individual sorption coolers will each be capable of providing a total of about 200 mW of cooling at 18 K and 1.4 Wat 20 K given passive radiative pre-cooling at 50 K. The hydrogen sorption coolers will directly cool the Low Frequency Instrument HEMT amplifiers to approximately 20 K and will also serve to intercept parasitics and pre-cool a RAL 4.5 K closed-cycle helium J-T cooler to 18 K for the separate High Frequency Instrument. To design the Planck sorption coolers a general sizing model and a detailed performance prediction model have been developed.

In this paper we describe the underlying relationships that determine the required size of a 18/20K hydrogen sorption cooler, and the approach utilized to model and optimize designs. In addition an initial comparison with the first data on a compressor element test will be presented while experimental data for the rest of the cooler components are not available and will be validated in the near future.