Fabrication and Testing of the Metal Hydride Sorbent Bed Assembly for a Periodic 10 K Sorption Cryocooler

Abstract

The Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE) is being developed for a future space shuttle flight to demonstrate 10 K sorption cooler technology in a microgravity environment. Three hydride beds circulate hydrogen through the various operation modes of the 10 K periodic cryocooler. Two beds, a fast absorption bed filled with LaNi4.8Sn0.2 alloy and a low pressure bed with ZrNi as the sorbent material, sequentially absorb hydrogen to drop the pressure from 0.25 MPa to below 0.2 kPa within two minutes. The low pressure bed also maintains the refrigerant pressure at <0.2 kPa as solid hydrogen sublimes with T<11 K. The third bed, which is filled with the LaNi4.8Sn0.2 alloy, collects the hydrogen from the other beds at nominal 0.1–0.15 MPa in order to compress it to 10 MPa for transfer to a storage reservoir. Each bed incorporates design features that enhance heat transfer and hydrogen gas flow in order to meet performance goals. The three hydride beds and the complete sorbent bed assembly (SBA) have been built and the beds were tested in the laboratory. During measurements under various reaction conditions including those that simulate flight operation, the hydride beds were found to have reversible hydrogen storage capacities that exceed the BETSCE system requirements. The hydrogen absorption kinetics permit the absorption of appropriate quantities of hydrogen to meet the cool down goal of 10 K within 2 minutes. The completed SBA has been integrated with the other components of the BETSCE cryogenic refrigerator for system ground testing.