Computational Simulation of Boil-Off Gas Formation inside Liquefied Natural Gas Tank Using Evaporation Model in ANSYS Fluent

Abstract

Research on the waste energy and emission has been quite intensive recently. The formation, venting and flared the Boil-off gas (BOG) considered as one of the contribution to the Greenhouse Gas (GHG) emission nowadays. The current model or method appearing in the literature is unable to analyze the real behavior of the vapor inside Liquefied Natural Gas (LNG) tank and unable to accurately estimate the amount of boil-off gas formation. In this paper, evaporation model is used to estimate LNG Boil-Off rate (BOR) inside LNG tank. Using User Define Function (UDF) hooked to the software ANSYS Fluent. The application enable drag law and alternative heat transfer coefficient to be included. Three dimensional membrane type LNG cargos are simulated with selected boundary condition located in the United States Gulf Coast based on average weather conditions. The result shows that the value of BOR agrees well with the previous study done with another model and with International Marine organization (IMO) standard which is less than 0.15% weight per day. The results also enable us to visualize the LNG evaporation behaviors inside LNG tanks.