THERMAL ANALYSIS ON CATALYST FILLED HEAT EXCHANGERS FOR ORTHO-PARA HYDROGEN CONVERSION

Hydrogen exists in two isomeric forms, namely para hydrogen and ortho hydrogen, which are determined by the spin direction of its two protons. These two isomers exhibit different energy levels, and their equilibrium ratio depends on the temperature. At room temperature (300K), the equilibrium ratio of para hydrogen is 0.25, which increases to 0.5 at 77K, and significantly rises to 99.8 at the liquefaction temperature (20.3K) under atmospheric pressure. During the hydrogen liquefaction process, it is essential to consider the conversion from ortho hydrogen to para hydrogen, as this transformation is an exothermic process. Neglecting the isomer conversion can lead to the evaporation of all the liquid hydrogen as the hydrogen reaches the ortho-para equilibrium ratio. To achieve both isomer equilibrium and cooling simultaneously, catalyst-filled heat exchanger is introduced. In this study, the influence of the thickness of the parting sheet and the width of the channel on the temperature and conversion of hydrogen was investigated in a 3-way catalyst-filled plate-fin heat exchanger to be installed in a 0.5-ton/day hydrogen liquefaction plant which is under construction in Korea. To describe the environment within the catalyst-filled heat exchanger, a porous medium was utilized, and the pressure drop was calculated based on Ergun's equation and empirical equation.