Study of vertical upward flame spread on charring materials—Part II: Numerical simulations
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Citations
Experimental study on downward flame spread characteristics under the influence of parallel curtain wall
Experimental study of vertically upward flame spread over polymethyl methacrylate slabs at different altitudes
Energy Balance Models of Downward Combustion of Parallel Thin Solid Fuels and Comparison to Experiments
Experimental study and heat transfer analysis of downward flame spread over PMMA under the effect of wall spacing
References
Application of a simple enthalpy-based pyrolysis model in numerical simulations of pyrolysis of charring materials
Study of pyrolysis and upward flame spread on charring materials-Part I: Experimental study
A pyrolysis model of charring materials considering the effect of ambient oxygen concentration
Comparison of simulated wet bench fires with small‐ and intermediate‐scale fire tests
Related Papers (5)
Study of pyrolysis and upward flame spread on charring materials-Part I: Experimental study
Flame Spread On Charring Materials: Numerical Predictions And Critical Conditions
Frequently Asked Questions (14)
Q2. What is the effect of heat on the mass flow rate?
The mass loss rate increases with decrease in the heat of pyrolysis, as the endothermic pyrolysis process consumes less energy, so that the pyrolysis front moves faster into the solid.
Q3. How long does the flame decay after the pyrolysis?
As soon as the pyrolysis ends, i.e. as soon as the pyrolysis front reaches the back surface, the flame heat flux decays exponentially from 10 kW/m 2 , with adecay time constant equal to flame = 30 s.
Q4. What is the effect of the set-up on the surface of the MDF board?
As the set-up is in principle symmetric, the net radiative heat exchange between the plates is relatively small, but the heat loss from each surface to the surroundings is certainly reduced.
Q5. What is the mass loss rate in the simulations?
In all samples, the mass loss rate in the experiments, prior to the onset of pyrolysis, is related to evaporation of unbound moisture.
Q6. What is the effect of h on the pyrolysis front?
As the material inside is then also already heated up more, the pyrolysis front moves faster during the early stages, leading to a higher first peak value in the mass loss rate.
Q7. How is the temperature of the front surface set?
For the convective boundary condition at the front surface, the ambient temperature is set to the initial room temperature (Tamb = 300 K) until pyrolysis takes place.
Q8. What is the reason for the small variations at the onset of pyrolysis?
The small variations at the onset of pyrolysis, after about 60 s, is due to the variation in the material properties, not due to a variation in boundary conditions (expressions (2a) and (2b)).
Q9. What is the quality of the results?
The quality of the results indicates that, provided the flame height and corresponding heat flux are known, the present pyrolysis model can be used to simulate vertically upward flame spread in a parallel plate configuration.
Q10. What is the temperature of the pyrolysis front?
As the surface temperature reaches the pyrolysis temperature (Tpyr = 325 o C = 598K), the temperature starts to rise more rapidly due to the additional heat flux from the flames (1b).
Q11. How much heat flux is assumed to be absorbed by the flames?
The authors assume the heat flux from the flames, absorbed by the material, constant throughout the experiment, equal to'' 2, 10 /flame absq kW m .
Q12. How is the heat exchange temperature at the front surface assumed to be?
From then on, until the end of pyrolysis, the surface is assumed to see flames, rather than air at approximately ambient temperature.
Q13. What is the mass loss rate for the dry samples?
In the experiments, the total mass loss per unitarea ranges between 8.7 kg/m 2 and 9.5 kg/m 2 for the dry samples and between 9.4 kg/m 2 and 10.2 kg/m 2 for the wet samples.
Q14. How much of the black body emissive power of the flames is the flame?
For flames of 700 o C (see below), this corresponds to a net absorption by the front surface of 20% of the black body emissive power of the flames.