One-dimensional model of pyrolysis and ignition of medium density fiberboard

subjected to transient irradiation

Izabella Vermesi Guillermo Rein

Department of Mechanical Engineering

Imperial College London

Gaurav AgarwalFM Global

Marcos ChaosLLNL

15.11.2016

Torremolinos, ES

Presentation Outline

1

Pyrolysis under

transient irradiation

Previous work with polymers

MDF: uses +

manufacture

MDF experiments

MDF model

Constant + transient

irradiation results

Parametric study

What is Pyrolysis?

2

Pyrolysis

= the process through which the solid undergoes a chemical

decomposition and transforms into a gaseous fuel

Importance of Pyrolysis

3

PYROLYSIS

Ignition

Flame spread

Constant vs. transient

4

0

5

10

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25

30

0 500 1000 1500

Hea

t F

lux [

kW

/m2]

Time [s]

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5

10

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20

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40

45

0 100 200 300 400 500

Hea

t F

lux [

kW

/m2]

Time [s]

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5

10

15

20

25

30

35

0 500 1000 1500

Hea

t F

lux [

kW

/m2]

Time [s]

Transient scenario: state of the art

5

• Linear ramps:

• Wood: Univ. Zaragoza (2000), USTC (2007), USTC (2016)

• MDF: FM Global (2016)

• Polymers: Univ. Edinburgh (2012)

• t2 parabolic heat flux:

• Wood: USTC (2016), Univ. Waterloo (2016)

• Parabolic pulses:

• Forest fuels: Univ. Exeter (2015)

• PMMA: Imperial College (2015)

• MDF: Imperial College (2016)

Vermesi et al., Combust. Fl. 2016

6

7

Vermesi et al., Combust. Fl. 2016

8

Vermesi et al., Combust. Fl. 2016

Medium density fiberboard

9

• Engineered wood product obtained from wood fibers glued

together under heat and pressure

• Use in the indoor built environment: furniture, separating

walls

http://ifabstudio.com/wp-content/uploads/2014/03/MDF_DETALE.jpg

MDF experiments

10

• FPA experiments using MDF samples with thickness of 30 mm

• Surface temperature measured with an IR pyrometer, mass

loss measured with load cell

Irradiation Curves

11

MDF model

12

• 1D model in Gpyro (Lautenberger, Fire Saf. J., 2009)

MDF

• Boundary conditions:

• Energy equation:

• Arrhenius equation for pyrolysis rate

MDF model

13

MDF model

14

MDF model

15

MDF results: constant irradiation

16

0

10

20

30

40

0

150

300

450

600

0 100 200 300 400 500

Irra

dia

tion [

kW

/m2]

Tem

per

ature

[°C

]

Time [s]

Measurement

Model Predictions

Irradiation

MDF results: constant irradiation

17

0

10

20

30

40

0

150

300

450

600

0 100 200 300 400 500

Irra

dia

tion [

kW

/m2]

Tem

per

ature

[°C

]

Time [s]

MeasurementModel PredictionsIrradiation

0

10

20

30

40

0

2

4

6

8

0 100 200 300 400 500Ir

rad

iati

on

[kW

/m2]

Mas

s lo

ss r

ate

[g/m

2s]

Time [s]

Measurement

Model Predictions

Irradiation

MDF results: transient irradiation

18

0

10

20

30

40

0

150

300

450

600

0 200 400

Irra

dia

tion [

kW

/m2]

Tem

per

ature

[°C

]

Time [s]

Measurement

Model Predictions

Irradiation

MDF results: transient irradiation

19

0

10

20

30

40

0

150

300

450

600

0 200 400

Irra

dia

tion [

kW

/m2]

Tem

per

ature

[°C

]

Time [s]

Measurement

Model Predictions

Irradiation

0

10

20

30

40

0

2

4

6

8

0 100 200 300 400 500Ir

rad

iati

on

[k

W/m

2]

Mas

s lo

ss r

ate

[g/m

2s]

Time [s]

MeasurementModel PredictionsIrradiation

Parametric study

20

• Thermal properties that remain constant with

temperature vs. temperature-dependent

properties

• Influence of the drying step in the kinetics scheme

Constant vs. temperature dependent properties

21

Influence of drying

22

Conclusions

23

• MDF subjected to transient irradiation ignited in all scenarios

• MDF experiments modelled in 1D in Gpyro (no optimization, only

values from literature and measurements)

• Surface temperatures are well predicted for both materials

• Mass loss rate is predicted qualitatively

• Drying is an essential step in modelling MDF

• Using temperature dependent properties improves the results slightly,

but is not as influential as drying

Thank you for your attention!

Questions?

24

Acknowledgements: