Numerical Analysis of Re-Liquefaction System for Liquefied CO2

Carbon capture, utilization, and storage (CCUS) has emerged as a key strategy for achieving net-zero greenhouse gas (GHG) emissions. In this context, the transportation of carbon dioxide (CO2) in liquid form is essential, requiring a re-liquefaction system to recondense the boil-off gas (BOG) generated during transport and storage. This study numerically investigates the thermal-fluid performance and operational stability of a liquefied carbon dioxide (LCO2) re-liquefaction system. One-dimensional thermal-fluid simulations were performed using Thermal Desktop (SINDA/FLUINT). The system model incorporated heat transfer mechanisms-conduction, convection, and radiation-as well as phase-change phenomena. Fluid properties were obtained from the NIST REFPROP database to ensure accurate representation under real operating conditions. The results indicate that periodic pressure control of both the storage tank and separator can be effectively maintained. During steady operation, approximately 4.5 kg/s of CO2 was processed, with about 75% successfully re-liquefied, primarily limited by throttling losses at the expansion valve. These findings confirm the thermodynamic stability of the proposed LCO2 re-liquefaction system and provide a foundation for future design optimization and validation of CCUS-based marine CO2 transport systems.