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A zonal non-equilibrium approach to model temperature gradients during ventless bottom filling of pressurized cryotanks for natural gas-powered ships

Thiaucourt, Jonas, Marty, Pierre, Hetet, Jean-François, Robert, Pascal, Delaire, Etienne
Energy 2019 v.188
computer software, emissions, equations, liquefied natural gas, liquids, models, shipping, ships, temperature profiles, thermodynamics, vapors
Liquefied Natural Gas (LNG) as a fuel is seen as a solution to curb harmful emissions in shipping and its quick uptake is now significant. New LNG bunkering scenarios are hence rising with a growing range of technical challenges. In this paper, a thermodynamic zonal model is established to assess the temperature gradients induced by a ventless bottom filling. The reservoir is divided into three control volumes. A condensation model at the liquid/vapor interface is proposed. Thermophysical properties are interpolated in tables allowing calculations with a good precision and a CPU time reduced of 68% compared to equation of state software direct calls. The non-equilibrium phenomenon of condensation blocking is highlighted. Then, the impact of the loading pressure is further investigated. As a result, it is shown that bottom filling rate at high pressure (around 11 bars absolute) can compete with vented filling techniques only if the tank can deal with strong spatial (liquid/vapor) and temporal temperature gradients, respectively of order 94.3 K and 0.19 K/s.