Postgraduate Seminar Presentation : CFD simulation of a full scale LNG storage tank

Speaker Abdullah Saleem (Supervisor: Prof Shamsuzzaman Farooq)

Host Department of Chemical and Biomolecular Engineering

Date/Time 11 Dec - 11 Dec, 11.00AM

Venue E5-02-32 , Faculty of Engineering, National University of Singapore

Synopsis

A well-insulated LNG (Liquefied Natural Gas) storage tank is a key facility in a regasification terminal. The management of Boil off Gas (BOG) produced from a LNG storage tank due to heat leak from the surrounding is an important issue. A comprehensive dynamic CFD model is presented in this study to thoroughly investigate an onshore full-scale LNG storage tank by analyzing internal flow dynamics and heat transfer characteristics owing to free convection. This study provides insights on the boiling phenomena and allows reliable quantification of BOG production. The ANSYS Fluent is used as solver for simulating a tank 80 m in diameter and 40 m high. An axisymmetric model is considered that accounts for the effect of gravity or static pressure. Vapor-liquid interface is tracked using the VOF (Volume of Fluid) method and the Lee model is employed to account for evaporation-condensation. The mixing characteristics in the liquid phase are analyzed and the steady state heat transfer coefficient at the vapor-liquid interface is evaluated. For a properly insulated full-scale tank, it is observed that evaporation occurs only at the vapor-liquid interface and no nucleate boiling is observed. The full-scale tank is also compared with small-scale tank to understand the differences in flow dynamics due to scaling. The critical wall superheat that marks the onset of bubble formation is also investigated.

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