극저온 LNG 저장탱크에서 벽면 거칠기가 열성층화 및 자가 가압 현상에 미치는 영향에 대한 수치해석

초록

This study numerically investigates the influence of wall roughness on thermal stratification and self-pressurization phenomena in cryogenic LNG storage tanks. A multiphase CFD model incorporating phase change and natural convection was developed based on a cylindrical Type C tank. Various surface roughness heights (  = 0.01 m and 0.05 m) were applied to the tank wall, and their effects on internal flow, thermal stratification, and pressure rise were analyzed. Results show that natural convection induces thermal stratification, which enhances evaporation at the free surface, consequently accelerating internal pressure increase. Wall roughness significantly suppressed the wall-side buoyant flow by increasing shear stress, which delayed stratification development and reduced free surface temperature. Despite identical total heat input, the final pressure rise was 43.1% lower than the smooth wall case, indicating that wall roughness can serve as a practical design variable for enhancing structural stability and reducing fuel loss in cryogenic storage systems.

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