June 22-27, 2014
Here, a novel approach to flameless venting is presented, which offers the possibility of improving the design of flameproof enclosures without reducing any safety aspects. This approach is based on the integration of porous structures – such as traditional sintered metals or sintered metal fibers – into the enclosure walls acting as venting and flame-quenching elements. It is shown that proper use of these structures can enormously decrease the maximum explosion pressure while safely avoiding flame transmissions, even for a large number of consecutive internal explosions. However, the transmission of a gas explosion through porous structures is a transient and spatially inhomogeneous process that is strongly influenced by turbulence and chemical reactions. Especially the heating of the structures due to hot gas flow and heat conduction may lead to hot surfaces which can act as ignition sources. Hence, various porous structures were investigated: First of all, their ability to relieve pressure and their stability concerning the maximum explosion pressure were examined. Their ability to avoid flame transmissions was determined by performing a standardized test for the non-transmission of an internal explosion. And, finally, the temperature and flow characteristics of these porous structures were investigated, too. Significant differences in flow resistance and heat conduction leading to different pressure relief and flame transmission behaviors were identified, depending on the specifics of the structure. In particular, the internal structure of the examined porous media, which results from porosity and pore size distribution as well as from the shape of the solid phase (matrix), affects these characteristics.
Julia Hornig, Detlev Markus, and Martin Thedens, "Porous structures used as flameproof pressure relief elements a novel approach of flameless venting" in "5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry", Prof. Kambiz Vafai, University of California, Riverside; Prof. Adrian Bejan, Duke University; Prof. Akira Nakayama, Shizuoka University; Prof. Oronzio Manca, Seconda Università degli Studi Napoli Eds, ECI Symposium Series, (2014). http://dc.engconfintl.org/porous_media_V/12