Feasibility Study of Heavy Gas Dispersion Experiments in Complex Environments in Physical Modelling

Abstract

Despite more than 50 years of research of accidental heavy gas releases, high qualitative and extensive reference data sets for heavy gas dispersions in complex environments are rare and knowledge gaps still persist. Accidental releases of heavy gases, mostly toxic or flammable, still pose severe health and environmental risks. This thesis presents a feasibility study of physical modelling of heavy gas dispersion experiments in complex environments and findings of heavy gas dispersion experiments. Measurements have been performed in the WOTAN boundary layer wind tunnel of the Environmental Wind Tunnel Laboratory of the Meteorological Institute of the University of Hamburg. Three models of increasing complexity are used to showcase the necessary planning and setup of a heavy gas dispersion scenario and how measurements are performed to successfully model a heavy gas dispersion. The model with the highest complexity is a part of a industrial chemical park in the city of Ludwigshafen of the company of BASF, which includes a multitude of different types of obstacles and buildings. Constraints and potential problems which can arise during a wind tunnel heavy gas dispersion measurement campaign are discussed and solutions to the potential issues are presented. The heavy gas dispersions are realised with a release of a CO2-butane mixture. Concentration measurements are performed with a flame ionisation detector. During the thesis more than 2000 flow measurements, 1200 neutral density and 1000 heavy gas dispersion measurements were performed in the three different model geometries. Measurements have been performed with variations in the wind tunnel boundary layer, wind direction, source volume flow and wind speed. In this thesis the influence of these factors, which effect heavy gas dispersions, are investigated and discussed. All flow, neutral density and heavy gas dispersion measurements, including the wind tunnel boundary layer measurements and model geometries are compiled in a reference data set which has been published.