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 m 3 /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 m 3 /h and 165 m 3 /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.

Experimental and numerical study of pool fire dynamics in an air-tight compartment focusing on pressure variation

“…The results illustrated that the pressure rise is an important issue to be considered in air-tight compartment fires. The over-pressures were also reported in simulation results [4,5,[7][8][9][10][11], which match well with experiments. A more detailed summary of fire-induced pressure build-up studies can be found in Ref.…”

“…8, where, the LEAK FO, LEAK AO and LEAK FA indicate the leakage from the fire room to the outside, the leakage from the adjacent room to the outside and the leakage from the fire room to the adjacent room through the gap at the bottom of the partition door, respectively. The leakage flow rate is dependent on the pressure difference and the leakage area [18]: (11) where is the leakage volume flow rate (m 3 /s), is the leakage area (m 2 ), is the pressure difference between the adjacent zones (Pa) and is the ambient air density (kg/m 3 ). Thus, the leakage flow rate has the same trend as the pressure variation.…”

Multi-scale analysis of the under-ventilated combustion regime for the case of a fire event in a confined and mechanically ventilated compartment

“…This revival of interest has led to the need for revisiting compartment fire with up-to-date research tools, both for experimental and numerical studies. Topics regarding pressure variations, extinction phenomena, and instabilities have been recently addressed [3], [4], [5], [6], [7], [8]. Among these studies, one of importance is the issue concerning reduced-scale modelling.…”

Influence of fire heat release rate (HRR) evolutions on fire-induced pressure variations in air-tight compartments

“…The recorded over-pressures range from 100 Pa to 1650 Pa in the fire experiments within 50 s from ignition [12]. On top of the experimental research, numerical studies also demonstrate the behavior of fire-induced pressure variations and assess the capability of Computational Fluid Dynamics (CFD) tools (e.g., Fire Dynamics Simulator, FDS) in predicting the fire-induced pressure variations [17,18]. Although this phenomenon has attracted attention, there is still a lack of systematic research on the factors that affect the fire-induced pressure variations, as well as a lack of experimental data for the validation of numerical results.…”