A LaNi5‐Hydride Thermal Absorption Compressor for a Hydrogen Refrigerator

The compound LaNi5 absorbs nearly 6 atoms of hydrogen per formula unit at an equilibrium pressure of 2.5 at and room temperature. LaNi5 exhibits a high rate of absorption and desorption of hydrogen and the heat of reaction is about 7.4 kcal/mol H2. The dependence of the equilibrium pressure in the two-phase region on temperature is utilized to compress hydrogen from 4 to 45 at, which are suitable working pressures for a hydrogen refrigerator. Three vessels containing LaNi5 are heated and cooled between 410 K and 290 K in cyclic operation. A system of selfoperating valves establishes a steady flow of hydrogen gas through a Joule-Thomson system. In the present design, employing precooling with liquid nitrogen at 78 K, 1 W of cold is produced at 26 K. Hydrogen-sorption properties of LaNi5 are given and the problems encountered in practical use of the material discussed.