Exploration of energy transfer and catalytic processes in continuous conversion heat exchangers for hydrogen liquefaction

Liquid hydrogen is increasingly recognized as a pivotal renewable energy carrier due to its high purity and volumetric density. However, the considerable energy consumption associated with current hydrogen liquefaction systems poses a significant challenge. Cryogenic heat exchangers, responsible for substantial exergy destruction, are key to improving efficiency. This study develops a theoretical model of a countercurrent heat exchanger with ortho-para hydrogen conversion, with results aligning well with experimental data. The investigation assesses the energy transfer properties and catalytic effects of various coolants, including helium, neon, and hydrogen, demonstrating superior performance due to its high specific heat capacity and thermal conductivity. Notably, peak conversion heat occurs near channel walls, driven by reaction kinetics, temperature gradients, and flow dynamics. The heat transfer coefficient with a cold fluid at 3 MPa is enhanced by 5 %, accompanied by a 3 % increase in the outlet para-hydrogen fraction compared to other conditions. This improvement arises from the synergistic interplay between specific heat capacity and cooling demand. Conversely, increasing hot fluid inlet pressure improves liquefaction yield but compromises the temperature differential and mass conversion efficiency. This study offers theoretical insights essential for the comprehensive performance optimization of continuous conversion hydrogen heat exchangers.