Residential and industrial buildings equipped with a ventilation system are complex facilities, where various heat and mass transfers could occur according to the operating conditions. In order to study these mass transfers, a methodology has been developed so as to carry out reduced-scale experiments for the study of isothermal flows, in steady or transient state. This methodology has been numerically and experimentally validated on simple configurations, and then applied to two standard configurations, representing nuclear facilities.
The wind influence on mass transfers inside these configurations, in normal, damaged
(stopping ventilation) or accidental (internal overpressure) situations, has been studied in the Jules Verne climatic wind tunnel of the CSTB. The wind effects, coupled or not with an internal overpressure, can lead to a partial or a total loss of the pollutant's containment inside buildings. Moreover, the wind turbulence can bring about instantaneous reversal leakage flowrates, which cannot be identified in steady state. In addition, the study of transient phenomena has highlighted the low influence of the branch inertia on transient flows, for typical values of real facilities. Finally, tracer tests have been carried out in order to study the pollutant dispersion inside a standard configuration subjected to wind, mechanical ventilation and internal overpressure effects.
The reliability of the zonal code SYLVIA, used notably to support safety assessment in
nuclear buildings, has been analyzed from these experimental results. The modelling of the physical phenomena experimentally observed has been validated, in steady and transient states. However, limitations have been identified for the study of pollutant dispersion, due to hypothesis used in SYLVIA code, as in all zonal codes (homogenous concentration inside rooms, instantaneous propagation inside branches and rooms).