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

• Published in: Fire safety journal 2021-12, Vol.126, p.103450, Article 103450
• Main Authors: Li, Junyi, Prétrel, Hugues, Beji, Tarek, Merci, Bart
• Format: Article
• Language: English
• Subjects: Air-tight compartment fire; Coefficients; Compartments; Decay; Decay rate; Engineering Sciences; Evolution; Fire dynamics; Gaseous fuels; Heat; Heat release rate; Heat transfer; Peak values; Pressure; Steady state; Vapor phases; Variation
• ISSN: 0379-7112; 1873-7226
• DOI: 10.1016/j.firesaf.2021.103450

The paper presents experimental results indicating the influence of the fire heat release rate (HRR) evolution on the fire-induced pressure variation in air-tight compartments, which increasingly appear in modern buildings. The fire evolution is stipulated according to a power law with variations in fire growth/decay rate coefficient, maximum steady state HRR, fire growth/decay exponent and fire duration. It is illustrated that the higher the fire growth/decay rate coefficient, the higher the over-pressure/under-pressure peaks become. The peak values approach a maximum level when the fire growth/decay rate coefficient exceeds a certain level (0.0926 kW/s2 in the present cases). Besides, the over-pressure and under-pressure peak values increase monotonously with the increase of the maximum steady state HRR. For cases with fire growth/decay exponent below 1, the pressure reaches peak values before the HRR reaches a steady state (maximum value or zero) because the net heat gained per unit time in the gas phase already reaches its peak values then. In cases with fire growth/decay exponent above 1, the pressure reaches peak values at the moment where the HRR reaches the steady state. Finally, in one test low-frequency oscillatory behavior is illustrated with gaseous fuel during the well-ventilated phase. •Comprehensive studies are conducted by parameterizing the heat release rate.•Increase in fire growth/decay rate causes the pressure to rise to a plateau level.•Higher maximum heat release rate leads to higher over-pressure and under-pressure.•The fire growth/decay exponent affects pressure variation and under-pressure peak.•Oscillatory behavior is reported with gaseous fuel in the well-ventilated phase.