Roles of catalysts’ porous media feature and catalytic conversion effect on the performance of plate-fin heat exchangers in hydrogen liquefaction

Abstract

Ortho-para hydrogen conversion is essential for hydrogen liquefaction and filling catalysts inside channels of plate-fin heat exchangers (PFHXs) is the most efficient method of conversion. However, the roles of the catalysts’ porous media feature and catalytic conversion effect on the performance of PFHXs filled with ortho-para hydrogen conversion catalysts are barely discussed. Three cases, i.e., Case A (normal PFHX), Case B (PFHX filled with non-catalytic particles acting as porous media), and Case C (PFHX filled with catalysts), are numerically studied and compared to illustrate the influence of filled ortho-para hydrogen conversion catalysts on the performance of the PFHX. The thermal-hydraulic performance coefficient (ηTHP) is defined to illustrate the combined performance of thermal (j factor) and hydraulic performance (f factor), and the conversion efficiency (ηCON) is defined to evaluate the conversion performance of the heat exchanger. The comparison between Case A and Case B shows that the particles acting as porous media restrain the hydraulic performance of normal PFHX while enhance the thermal performance. In comparison with Case B, as the ortho-para hydrogen conversion effect is considered in Case C, j factor is reduced by 1.8 % and the flow resistance is increased by 8.9 %, denoting that the conversion heat leads to deterioration of heat transfer and hydraulic performance. Parametric analyses show that, when the Reynolds number rises from 214.0 to 1569.1, ηTHP and ηCON in Case C increase by 304.9 % and 10.2 % respectively, implying that the Reynolds number is quite influential to the performance. Beside, the proportion of conversion heat in the total heat flux rises along the flow direction and tends to level off, reaching about 45 %.