Development of a 1 L/h Scale Liquid Hydrogen System

Abstract

A small-scale hydrogen liquefaction plant consists of cryocooler, cryostat, liquid nitrogen (LN2) precooling bath, two ortho-para (o-p) hydrogen converters, a heat pipe, multilayer insulations (MLI), sensors and auxiliary components. The liquefaction plant was designed as both a cryocooler-cooled liquefier and a long-term zero boil-off liquid storage reservoir. A Gifford-McMahon (GM) cryocooler was selected as a cold sink and purchased from Cryomech Inc. A vacuum-jacketed 200 L capacity cryostat was designed to provide highly efficient thermal protection to LH2 storage space. A heat pipe was uniquely designed and installed in the cryostat to enhance heat transfer between the cryocooler and hydrogen gas and liquid. A LN2-cooled precooling bath was designed to act as a precooler and an o-p hydrogen converter. MLT blankets with hydrogen getter under high vacuum in the cryostat minimize heat loss into LH2 storage. All the components were carefully assembled in dust, oil and solvent-free environment with extra caution of vacuum tightness followed by dry nitrogen and helium purge. After initial cool-down of the cryocooler under vacuum, 99.999% of 300 K hydrogen gas was introduced to the liquefaction plant. From a series of liquefaction tests with or without LN2 precooling, the hydrogen liquefaction plant successfully demonstrated 1.4 L/h of hydrogen liquefaction with LN2 precooling and two o-p hydrogen converters, and 0.7 L/h without LN2 precooling. ？ 2015 World Scientific Publishing Company.