Volkmar Schröder

Explosion behaviour of the ‘non-flammable’ CFC substitute 1,1,1,2-tetrafluoroethane (R134a)

The explosion ranges of R134a/nitrogen/oxygen mixtures have been investigated at atmospheric pressure. The results of these full flammability tests at 20 °C and at 280 °C are presented in a triangular diagram. In addition, the influence of pressure on the flammability of R134a/air mixtures has also been studied. Under normal conditions, R134a is a non-flammable gas but exhibits an explosion range at higher oxygen percentages than those in air. At increased temperatures or pressures, R134a also has an explosion range in air, i.e. without any higher oxygen percentage. Using a detonation tube, the detonability of R134a/air mixture has been investigated for pressures between 8–20 bar and temperatures from room temperature to 200 °C. Stable detonations with detonation velocities of 1506–1535 m s−1 were initiated by incoming detonation waves. For an oxygen-enriched R134a/nitrogen/oxygen mixture at 10 bar, using a glowing wire as the ignition source a pressure-pilling effect was observed. In this experiment a pressure of more than 1200 bar was attained.

Measurement and Prediction of the Inert Gas Influence on Explosion Limits for Ethylene/Nitrogen/Air and Ethylene/Carbon‐Dioxide/Air Mixtures at Elevated Pressures

To determine the explosion limits of combustible gas/inert-gas/air mixtures at elevated initial pressures and/or temperatures, a high experimental effort is necessary. No standard test method exists and values are rarely to find in the literature. In order to reduce the large number of experiments, models suitable for simulating the inert gas influence on explosion limits at elevated pressure have been developed. In this work, an experimental method to determine the explosion limits at elevated pressures and the simulation of the inert gas influence of nitrogen and carbon dioxide on the explosion limits of C 2 H 4 /air mixtures are presented.

Dispersion of heavy gases – Experimental results and numerical simulations

The hazardous potential of accidental heavy gas releases, especially those involving flammable and toxic gases, is widely known. In order to predict the area in which these gases are in hazardous concentrations, an estimation of the dispersion of these gases must be carried out. While the hazardous area for flammable heavy gases is determined by the lower flammability limit (ca. >1 vol%), the release of toxic heavy gases can result in a much larger hazardous area. Toxic gases, even in very low concentrations (ca. <3,000 ppm), have the potential to be highly damaging. State‐of‐the‐art dispersion models, such as the VDI Guideline 3783, can be used to estimate the dispersion of heavy gases. However, VDI 3783 gives no method for the prediction of the height and width of a heavy gas cloud, which are both required for quantitative risk analysis as well as for a possible coupling of a Lagrangian particle model with the VDI 3783 heavy gas dispersion model. Therefore, further calculation methods were used to describe these dimensions and were evaluated against experimental studies of the length, width, and height of the heavy and neutral gas field. In addition to that the influence of the source height on the heavy gas dispersion was also examined.