Effect of catalytic structures on fluid flow and heat transfer characteristics using structure-resolved CFD simulations

Recent advancements in additive manufacturing have enabled the fabrication of complex catalytic structures with a high surface area to volume ratio such as triply periodic minimal surface (TPMS) based structures. However, the flow and heat transfer characteristics of these TPMS-based structures require further investigation for their effective application in solid-catalyzed gas-phase reactions. In the present study, we have performed structure-resolved CFD simulations of TPMS-based structures to understand flow and heat transfer characteristics. Further, their performance is compared with a few conventional monolithic structures (comprised of triangular, hexagonal and internal finned channels) in terms of pressure drop (ΔP), velocity and temperature distribution. We observed higher ΔP for TPMS-based structures compared to monolithic structures due to increased flow resistance provided by their geometric configuration. Whereas, the TPMS-based structures exhibited superior heat transfer performance, characterized by relatively uniform temperature distribution, attributed to enhanced fluid intermixing. Further, the local and bed-scale heat transfer characteristics are quantified using lateral and axial heat transfer coefficients (h_l, h_a) and bed Biot number (Bi_bed). A higher h_l and h_a of TPMS-based structures depicted the higher convective heat transport due to improved fluid intermixing. Additionally, Bi_bed < 20 suggests limited convective heat transport in the monolithic structures, while Bi_bed > 30 represents dominant convective heat transport in TPMS-based structures. The TPMS-based structures showed excellent heat transfer performance for different reaction conditions (from mild to severe heat effects). Additionally, geometric modifications to conventional triangular channels by enabling fluid intermixing led to improved heat transfer performance.