High Efficiency Particulate Air (HEPA) pleated filters are used to ensure the containment of airborne contamination within nuclear facilities. These filters are often the last barrier before a potential release of radioactive substances into the environment. Predicting their performances (pressure drop and efficiency) is a main thrust of research for IRSN which aims at avoiding any unexpected failure of those devices on French nuclear facilities.
The clogging phenomenon is mainly influenced, on one side, by the flow conditions imposed in the ventilation network and, on the other side, by the media characteristics and the particles properties which are collected by the filter. Consequently, the work carried out has been divided into two parts:
In the first part, we focused on the study of the airflow behavior within a HEPA pleated filter with an experimental and numerical approach. An experimental bench has been developed to measure the airflow field at the entrance channel of a HEPA filter pleat. Then, the experimental measurements have been used to validate GeoDict® and ANSYS CFX® simulations. The combination of the experimental and the numerical results have been used to develop a model to predict the evolution of the initial HEPA filter pressure drop.
The work performed in the second part deals with the clogging of the filter. An experimental bench, dedicated to the characterization of the parameters that intervene in the clogging models such as the porosity, the pressure drop and the particles size, has been developed. Then, Numerical simulations conducted with GeoDict® have been realized to describe the cake formation on the surface of a HEPA pleated filter. Finally, we developed a model to predict the evolution of HEPA pressure drop during clogging with micronic particles.