Surface Evaporation of Cryogenic Liquids, Including LNG and LPG

Abstract Surface evaporation of the boil-off gas is the key to understanding how stratification and rollover can take place. 

The chapter concentrates on the evaporation mechanism which is controlled by superheated convection currents at the tank wall carrying all the heat inflows up to the liquid surface. 

Research studies have shown how the surface evaporation mass flow depends on a thin surface layer with a sensitive thermal impedance which can be strongly influenced by mechanical and convectional disturbances. Rollover and other evaporation instabilities are a consequence. 

For LNG mixtures, the surface evaporation impedance of methane is much lower than for ethane, so the vapour has a higher methane content than predicted by standard (T-x) data. 

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