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Performance of very high efficiency filters as a function of relative humidity

Aurélie JOUBERT, doctorate of Institut national polytechnique de Lorraine, 190 p., defended on the 13th november 2009

Document type > *Mémoire/HDR/Thesis

Keywords > thermohydraulics, GUI, relative humidity, classification tree, Rayleigh’s equations

Research Unit > IRSN/DSU/SERAC/LECEV

Authors > JOUBERT Aurélie

Publication Date > 13/11/2009

Summary

Pleated High Efficiency Particulate Air (HEPA) filters are used for maintaining the containment of radioactive substances in nuclear plants; thus, they are sensitive elements of nuclear safety. Some accidental situations, such as the emergence of a hole on a pipe with release of steam, can lead to a high increase of the air humidity. This work can overcome the lack of analytical data in the literature regarding the behaviour of pleated HEPA filters, in terms of changes in pressure drop and efficiency, in presence of humidity (unsaturated air).
Experimental clogging tests have been performed on a test bench with two aerosols: nonhygroscopic micronic alumina particles and hygroscopic submicronic sodium chloride particles. The results showed that the influence of humidity during the clogging of a HEPA filter depends on several parameters: the geometry of the filter (plane or pleated), the size distribution and hygroscopicity of the aerosol clogging and finally the interaction time between the aerosol and humid air. Measurements of efficiency of clean and clogged filters (at different degrees of clogging), performed with the normalized soda fluorescein aerosol, are also sensitive to the presence of more or less relative humidity in the air. Finally, all results helped to develop an empirical model for estimating the evolution of the pressure drop of HEPA filters; this model is applicable during the formation of the particulate cake in presence of humidity without reducing of the surface area filtration.

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Jean-Claude Laborde, the thesis supervisor

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Mémoire de thèse


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