Analysis of Heat and Smoke Propagation and Oscillatory Flow through Ceiling Vents in a Large-Scale Compartment Fire

Claudio Zanzi,Pablo Gómez,Joaquín López,Julio Hernández

doi:10.3390/app9163305

Claudio Zanzi, Pablo Gómez + Show 2 more

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https://doi.org/10.3390/app9163305

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Abstract

One question that often arises is whether a specialized code or a more general code may be equally suitable for fire modeling. This paper investigates the performance and capabilities of a specialized code (FDS) and a general-purpose code (FLUENT) to simulate a fire in the commercial area of an underground intermodal transportation station. In order to facilitate a more precise comparison between the two codes, especially with regard to ventilation issues, the number of factors that may affect the fire evolution is reduced by simplifying the scenario and the fire model. The codes are applied to the same fire scenario using a simplified fire model, which considers a source of mass, heat and species to characterize the fire focus, and whose results are also compared with those obtained using FDS and a combustion model. An oscillating behavior of the fire-induced convective heat and mass fluxes through the natural vents is predicted, whose frequency compares well with experimental results for the ranges of compartment heights and heat release rates considered. The results obtained with the two codes for the smoke and heat propagation patterns and convective fluxes through the forced and natural ventilation systems are discussed and compared to each other. The agreement is very good for the temperature and species concentration distributions and the overall flow pattern, whereas appreciable discrepancies are only found in the oscillatory behavior of the fire-induced convective heat and mass fluxes through the natural vents. The relative performance of the codes in terms of central processing unit (CPU) time consumption is also discussed.

Highlights

Performance-based design (PBD) principles are commonly used to draw up fire protection plans [1]
This section looks at the results obtained from the simulation of the scenario described in Section 3.2 using the Fire Dynamics Simulator (FDS) and FLUENT codes with the simplified fire model and the default
We analyze the predictions of FDS with the simplified fire model, considering four combinations of the inlet temperature, Tin, and mass flow rate, ṁin, of the mixture of gases introduced in the computational domain

Summary

Introduction

Performance-based design (PBD) principles are commonly used to draw up fire protection plans [1]. The results of the corresponding tests will help in drawing up protection, extinction and evacuation plans, perhaps even suggest improvements in the infrastructures themselves [3,4,5]. The main inconvenience of this approach is the expense involved in full-scale experiments. Computational tools have contributed much to PBD in the case of confined areas such as stations, road tunnels, underground carparks shopping centres and stairwells of high-rise buildings [6,7,8,9,10]. Examples of reviews on field and zone approaches, turbulence, combustion, radiation, soot production and fire modeling in such scenarios can be found in [11,12]

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