Non-equilibrium theories for macroscale heat transfer: ablative composite layer systems

Puiroux, Nicolas; Prat, Marc; Quintard, Michel

doi:10.1016/j.ijthermalsci.2003.11.004

Cited by 24 publications

(13 citation statements)

References 24 publications

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“…If local mass equilibrium models have received a large attention in the past due their simplicity [e.g., Kansa et al [25]; cf. Morales-Zarate et al [37] for the application to a reactive three-phase system], specific precaution must be taken with reactive systems for which the assumption of small gradients is sometimes hard to verify [44,33]. Intrinsically, indeed, the presence of reactive source terms induce concentration gradients which can be more or less important.…”

Section: Discussionmentioning

confidence: 99%

“…A commonlyadopted approach to this coupling is to utilize a quasi-steady assumption; this implies that the evolution of the system geometry occurs on a time scale large compared with the time scale for mass transfer processes [58,42]. This time-evolving interface problem is similar to the one encountered in dissolution/precipitation [20] or in combustion in porous media [25,44,33], to cite only those, for which the quasi-steady assumption is classically adopted.…”

Section: Microscale Modelmentioning

confidence: 99%

See 1 more Smart Citation

Biofilms in porous media: Development of macroscopic transport equations via volume averaging with closure for local mass equilibrium conditions

Golfier

Wood

Orgogozo

et al. 2009

Advances in Water Resources

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Section: Discussionmentioning

confidence: 99%

Section: Microscale Modelmentioning

confidence: 99%

Biofilms in porous media: Development of macroscopic transport equations via volume averaging with closure for local mass equilibrium conditions

Golfier

Wood

Orgogozo

et al. 2009

Advances in Water Resources

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“…Refs. [184,185]. However, in most fire-related studies it is assumed that the solid and gaseous phases are in thermal equilibrium due to the much smaller volumetric heat capacity of the volatiles [70][71][72].…”

Section: Convection Advection and Diffusionmentioning

confidence: 99%

Generalized pyrolysis model for combustible solids

Lautenberger

Fernandez-Pello

2009

Fire Safety Journal

307

259

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This dissertation presents the derivation, numerical implementation, and verification/validation of a generalized model that can be used to simulate the pyrolysis, gasification, and burning of a wide range of solid fuels encountered in fires. The model can be applied to noncharring and charring solids, composites, intumescent coatings, and smolder in porous media. Care is taken to make the model as general as possible, allowing the user to determine the appropriate level of complexity to include in a simulation. The model considers a user-specified number of gas phase and condensed phase species, each having its own temperature-dependent thermophysical properties.Any number of heterogeneous (gas-solid) or homogeneous (solid-solid or gas-gas) reactions can be specified. Both in-depth radiation transfer through semi-transparent media and radiation transport across pores are considered. Volume change (surface regression or swelling/intumescence) is handled by allowing the size of grid points to change as dictated by mass conservation. All volatiles generated inside the solid escape to the ambient with no resistance to mass transfer unless a pressure solver is invoked; the resultant flow of volatiles is then calculated according to Darcy's law. A gas phase 2 convective-diffusive solver can be invoked to determine the composition of the volatiles.Oxidative pyrolysis is simulated by modeling diffusion of oxygen from the ambient into the pyrolyzing solid where it may participate in reactions. Consequently, the mass flux and composition of volatiles escaping from the solid can be calculated. To aid in determining the required input parameters, the model is coupled to a genetic algorithm that can be used to estimate the required input parameters from bench-scale fire tests or thermogravimetric analysis.

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“…According to Puiroux [20], solid and gas phases are in thermal equilibrium as long as the Péclet number for diffusion of heat within the pores is small (P e = g ρ g c p,g d p v g /k g ). In most of the applications of interest for space agencies, the small pore size (< 100µm) and the slow pyrolysis gas flow (v g ∼ 1m/s) insure a small Péclet number: the gas temperature accommodates to the solid temperature within the pores [5].…”

Section: Iiic Energy Conservationmentioning

confidence: 99%