Modeling of panel inertia effects in vented dust explosions

Abstract

Current guidelines for sizing of vents in dust explosions deal with panel inertia effects either by suggesting that the issue be approached experimentally on a case-by-case basis (VDI 3673) or by recommending a maximum mass per unit area (NFPA 68). This empirical approach to the problem is surprising, given that this aspect of explosion venting should be easily amenable to analytical treatment. From this assessment, an analysis of vent panel dynamics was carried out based on a simplified explosion model, which has also been used to develop a generalized vent sizing correlation. The main result of the analysis is the identification of a dimensionless parameter which fully characterizes the effects associated with the inertia of the panel. This inertia parameter includes: the reactivity of the mixture; the volume of the enclosure; the mass of the vent per unit area; the number of equal panels on the vented volume; and a panel shape factor. The analysis has quanitified the intuitive expectation that the mass per unit area of the panel is not a property that should be considered in isolation, and that panel inertia effects are more important the more reactive the mixture and the smaller the volume. The predictions from the model have been validated by comparison with available data for both dust and gas explosions. The extensive validation work that has supported their development provides confidence that the design correlations derived from the analysis can be used reliably to account for an effect that is either neglected or referred to testing by existing guidelines.