Analytical solutions for the isobaric evaporation of pure cryogens in storage tanks

Abstract

New analytical solutions have been derived for the isobaric evaporation of a pure liquid cryogen. In particular, expressions have been provided for the liquid volume, evaporation rate, Boil-off-Gas (BOG) rate, vapour temperature and vapour to liquid heat transfer rate as a function of time. Both equilibrium and non-equilibrium scenarios have been considered. In the former, the vapour and liquid cryogen are assumed to be in thermal equilibrium, while in the latter the vapour is treated as superheated with respect to the liquid and acts as an additional heat source.The derived solutions for two scenarios were validated against the numerical results for the evaporation of liquid methane and of liquid nitrogen in small, medium sized and large storage tanks that are used in industry. For the equilibrium model, the analytical solutions are exact. For the non-equilibrium model, the analytical solutions are valid for the whole duration of evaporation, except for a short transient period at the beginning of the evaporation. For physical quantities of industrial interest, they provide accurate estimates of liquid volume, BOG rate and BOG temperature, with the maximum deviations not exceeding 1%, 2% and 4.5%, respectively. The vapour to liquid heat transfer rate is also well predicted to within a maximum deviation of 5%.

Experimental Study of Ship Motion Effect on Pressurization and Holding Time of Tank Containers during Marine Transportation

“…Static evaporation characteristics in cryogenic vessels have been studied using theoretical, CFD, and experimental methods. In theoretical studies, predictions of LNG composition and BOG rate were studied based on equilibrium [5][6][7][8] and non-equilibrium [9][10][11] thermodynamics. In CFD studies, temperature distributions, heat transfer, and evaporation mechanics have been investigated [12][13][14].…”

Study on thermodynamic response in liquefied natural gas storage tanks under static pressurization and sloshing conditions

“…The measured results showed that fluid thermal stratification is highly related to the thermal aspect ratio. Huerta and Vesovic 28,29 developed an analytical method to evaluate the evaporation rate of pure cryogen. The results showed that the initial liquid filling has obvious effects on the boil-off rate of pure cryogen.…”