CFD study of fire-induced pressure variation in a mechanically-ventilated air-tight compartment

Abstract

Computational Fluid Dynamics (CFD) simulations of fire-induced pressure and ventilation flow in a mechanically-ventilated air-tight compartment, representative of a passive house, are presented. Experiments conducted by University of Mons are used to assess the results. The simulation heat release rate is prescribed based on experimental measurements. The experimental duct flow rate is about 80 m3/h. Two methods are used to meet the aforementioned value in simulations: 1) by modeling the actual fan curve and dampers, and 2) by modifying the fan curve to avoid simulations of dampers. The combination of real fan curve and dampers provides better results. The simulations reproduce well the pressure profile (maximum 433 Pa) and the duct flows. The simulated reverse inlet flow and increased outlet flow rates reach values of 157 m3/h and 165 m3/h, respectively. Besides, the fire-induced pressure is high enough to hinder evacuation and fire rescue operations due to the impossibility of opening inward-open doors. Moreover, the adjacent room pressure also reaches a high level. Reducing the gap area between rooms significantly reduces the adjacent room pressure, but leads to an increase of the fire room pressure. Temperature deviations are observed and are improved by modeling a more realistic fire source.