Accidental spill of cryogenic liquids like liquefied natural gas (LNG) or liquid nitrogen (LIN) on the ground undergo vigorous boil off due to large temperature difference between the liquid and the ambient condition. Three different boiling regimes can be observed during the spill: film boiling, transition and nucleate boiling. Heat transfer correlations obtained from the literature were applied to build numerical model of boiling cryogenic liquid spilled on a solid. Different combinations of liquid-solid systems were studied utilizing methane, hydrogen, oxygen and nitrogen on the solid substrates: concrete, soil, aluminium and polystyrene. The boiling curves were generated for a given liquid-solid system and the results were analysed to determine the possibility of occurrence and the duration of each regime during the accidental spill. The analyses show how long each boiling regime can theoretically last for each case. The boiling regime model was compared to simple one-dimensional (1D) "ideal" conduction model, which assumes a semi-infinite solid, heat flux in one direction only and perfect thermal contact at the liquid-solid interface (which leads to constant surface temperature for the solid substrate which is equal to the liquid boiling point). Subsequently, the 1D "ideal" conduction model was modified and extended to account for non-ideal contact at the liquid-solid interface, providing additional resistance for heat transfer to the cryogenic pool. A set of laboratory and medium scale experiments were performed at the laboratory of Texas A&M University at Qatar and at the Ras Laffan Industrial City (RLIC), Doha, Qatar to provide the validation of these models. The experiments were performed utilizing liquid nitrogen spilled on concrete. To study the effect of surface roughness on vaporization rate of liquid nitrogen, laboratory scale experiments were conducted on rough and smooth concrete surfaces. The vaporization rate was determined directly from the mass loss monitored during the experiments. The film, transition and nucleate boiling regimes were observed during the laboratory scale experiments and nucleate boiling regime was observed in the medium scale experiments. These experiments were used to validate relevant models. Specific heat of the concrete was determined independently by Differential Scanning Calorimetry (DSC) and thermal conductivity was measured by Guarded Hot Plate (GHP) method.
|Journal||Institution of Chemical Engineers Symposium Series|
|Publication status||Published - 2015|
- Boiling regimes
- Liquid Nitrogen
ASJC Scopus subject areas
- Chemical Engineering(all)