Nirupama Gopalaswami

Small-scale experimental study of vaporization flux of liquid nitrogen released on water.

A small-scale experimental study was conducted using liquid nitrogen to investigate the convective heat transfer behavior of cryogenic liquids released on water. The experiment was performed by spilling five different amounts of liquid nitrogen at different release rates and initial water temperatures. The vaporization mass fluxes of liquid nitrogen were determined directly from the mass loss measured during the experiment. A variation of initial vaporization fluxes and a subsequent shift in heat transfer mechanism were observed with changes in initial water temperature. The initial vaporization fluxes were directly dependent on the liquid nitrogen spill rate. The heat flux from water to liquid nitrogen determined from experimental data was validated with two theoretical correlations for convective boiling. It was also observed from validation with correlations that liquid nitrogen was found to be predominantly in the film boiling regime. The substantial results provide a suitable procedure for predicting the heat flux from water to cryogenic liquids that is required for source term modeling.

Experimental and numerical study of liquefied natural gas (LNG) pool spreading and vaporization on water

The investigation of pool spreading and vaporization phenomenon is an essential part of consequence analysis to determine the severity of LNG spills on water. In this study, release of LNG on water during marine operations is studied through experimental and numerical methods The study involves emulation of an LNG leak from transfer arms during side by side loading operations. The experimental part involves flow of LNG in a narrow trench filled with water and subsequent measurement of pool spreading and vaporization parameters. The numerical part involves CFD simulation using a three dimensional hybrid homogenous Eulerian multiphase solver to model the pool spreading and vaporization phenomenon. In this method, LNG is modeled as dispersed phase droplets which can interact with continuous phases - water and air through interphase models. The numerical study also employs a novel user-defined routine for capturing the LNG vaporization process. The CFD solver was capable of capturing the salient features of LNG pool spreading and vaporization phenomena. It was observed from experiment and CFD simulation that wind influenced both pool spreading and vaporization phenomenon through entrainment and convection.