Impact of ash layer retention on heat transfer in piles of vegetation and structure firebrands

Wong, Steven; Hodges, Jonathan L.; Lattimer, Brian Y.

doi:10.1016/j.firesaf.2022.103694

Cited by 4 publications

(7 citation statements)

References 25 publications

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“…CFD studies were conducted on three firebrand configurations (single, horizontal array, and vertical array) for two different firebrand aspect ratios and different flow velocities. The mass loss and surface temperature data were validated with experimental results from the studies by Lattimer et al 24 and Wong et al 25 Although heterogeneous kinetics were not modeled, the CFD results predicted the controlling physics quite accurately. Using the CFD results, the role played by the convection and kinetic-driven processes in char oxidation is also discussed.…”

Section: Introductionmentioning

confidence: 70%

“…The CFD model was validated with experimental results presented in the works by Lattimer et al 24 and Wong et al 25 The authors conducted a series of experiments wherein cylindrical, structured wood pieces were set aflame. After the firebrands were charred and stopped flaming, they were placed at the exit of a wind tunnel.…”

Section: Methodsmentioning

confidence: 99%

“…Wong et al 25 measured the temperatures for Tests 7 and 8 using both the top and front IR cameras. The authors also measured the heat flux onto a surface using inverse heat transfer analysis.…”

Section: Methodsmentioning

confidence: 99%

“…In the structured firebrands, the ash layer is not retained on the firebrand. 25 Thus, the char core keeps shrinking while the ash layer keeps shedding off of the surface (i.e. the firebrand diameter is shrinking).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…Experimental measurements of these quantities are especially challenging since the gradients of these properties are very high along the firebrand surface. 25 Furthermore, variations of heat and mass transfer coefficients on the surface of a firebrand are hard to quantify experimentally. The aim of this article is to develop a conjugate heat and mass transfer-based computational fluid dynamics (CFD) approach for predicting local effects during char oxidation in convective-driven processes.…”

Section: Introductionmentioning

confidence: 99%

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A computational fluid dynamics model to estimate local quantities in firebrand char oxidation

Banagiri,

Meadows,

Lattimer

2023

Journal of Fire Sciences

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Firebrand burning is a complex phenomenon that is influenced by several parameters which are difficult to fully explore experimentally. Computational fluid dynamics models capable of predicting local quantities are essential for accurate prediction of char oxidation in firebrands. This article presents a computational fluid dynamics model to estimate firebrand mass loss, diameter change, and surface temperature during char oxidation. The model was validated using previously conducted wind tunnel experiments. These experiments were conducted for firebrands of two different aspect ratios, which were arranged in three different configurations (single, horizontal array, and vertical array), and for four different wind speeds (0.5, 1, 1.5, and 2 m/s). The computational fluid dynamics results were compared with a previous 1 D model. In all the test cases, the computational fluid dynamics model predicted the physical phenomena with significantly improved accuracy compared to a 1 D model. The char oxidation model presented in this article can be coupled with other models to study firebrand generation and trajectory, biomass pyrolysis, fluidized bed reactors, and coal combustion.

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Section: Introductionmentioning

confidence: 70%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A computational fluid dynamics model to estimate local quantities in firebrand char oxidation

Banagiri,

Meadows,

Lattimer

2023

Journal of Fire Sciences

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A review of thermal exposure and fire spread mechanisms in large outdoor fires and the built environment

Filkov¹,

Tihay‐Felicelli²,

Masoudvaziri³

et al. 2023

Fire Safety Journal

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Firebrand burning under wind: an experimental study

Yan,

Liu,

Zhu

et al. 2024

Int. J. Wildland Fire

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Background Spot fires play a significant role in the rapid spread of wildland and wildland–urban interface fires. Aims This paper presents an experimental and modelling study on the flaming and smouldering burning of wood firebrands under forced convection. Methods The firebrand burning experiments were conducted with different wind speeds and firebrand sizes. Key results The burning rate of firebrands under forced convection is quantified by wood pyrolysis rate, char oxidation rate and a convective term. The firebrand projected area is correlated with firebrand diameter, char density, wind speed, and flaming or smouldering burning. A surface temperature model is derived in terms of condensed-phase energy conservation. We finally establish a simplified firebrand transport model based on the burning rate, projected area and surface temperature of firebrands. Conclusion The mass loss due to wood pyrolysis is much greater than that due to char oxidation in self-sustaining burning. The burning rate is proportional to U1/2, where U is wind speed. The projected area for flaming firebrands decreases more rapidly than that for smouldering ones. The firebrand surface temperature is mainly determined by radiation. Implications Knowledge about firebrand burning characteristics is essential for predicting the flight distance and trajectory in firebrand transport.

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Impact of ash layer retention on heat transfer in piles of vegetation and structure firebrands

Cited by 4 publications

References 25 publications

A computational fluid dynamics model to estimate local quantities in firebrand char oxidation

A computational fluid dynamics model to estimate local quantities in firebrand char oxidation

A review of thermal exposure and fire spread mechanisms in large outdoor fires and the built environment

Firebrand burning under wind: an experimental study

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