Abstract
This work is devoted to analyzing the behavior of dry wooden bodies during pyrolysis and ignition. A new treatment for defining criticality of this problem has been applied here. Critical conditions in different planes, using the definitions of criticality, are presented. The effects of different mechanisms and parameters such as the heat transfer to the wooden body, volatile gases, the initial temperature of the body, and the heat of pyrolysis on ignition characteristics have been obtained. The temperature and mass loss histories of the wooden body are presented based on a numerical solution to the heat and mass balance equations. The numerical solution shows good agreement with that predicted from the analytical one. The relation between the ignition temperature, ignition time, and the controllable parameters which effect on the critical ignition conditions are generated and discussed. Satisfactory generic qualitative results have been achieved in the absence of either physical or chemical kinetic data for the reactant.
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Abbreviations
- A 0 :
-
Pre-exponential factor (s−1)
- A p :
-
Particle surface area (m2)
- \(B = R\dot{Q}\backslash E\rho_{0} V_{\text{p}}{{C_{\text{p}} }} A_{0}\) :
-
Dimensionless heat transferred rate
- C D, W :
-
Specific heat of dry wood (J kg−1 K−1)
- C p :
-
Specific heat of wood (J kg−1 K−1)
- C v :
-
Specific heat of volatile matter (J kg−1 K−1)
- E :
-
Activation energy (J mol−1)
- h :
-
Heat transfer coefficient (W m−2K−1)
- k :
-
Thermal conductivity (W m−1 K−1)
- q :
-
Exothermic pyrolysis heat of reaction (J/kg)
- \(\dot{Q}\) :
-
Heat transferred rate to the particle (W)
- R :
-
Universal gas constant (J mol−1 K)
- t :
-
Time (s)
- T :
-
Temperature (K)
- V :
-
Volume (m3)
- \(\alpha = qV_{\text{p}} \rho_{0} A_{0} /\dot{Q}\) :
-
Dimensionless pyrolysis heat
- \(\gamma = R\dot{Q}/A_{0} C_{\text{v}} EV_{\text{p}} \rho_{0}\) :
-
Dimensionless volatile matter heat
- ρ :
-
Instantaneous particle density (kg m−3)
- ρ r = ρ/ρ f :
-
Density ratio
- θ = RT/E :
-
Dimensionless temperature
- \(\tau = R\dot{Q}t/EC_{\text{p}} \rho_{0} V_{\text{p}}\) :
-
Dimensionless time
- *:
-
Critical
- comb:
-
Combined
- conv:
-
Convection
- f:
-
Final
- ig:
-
Ignition
- m:
-
Maximum
- 0:
-
Initial condition
- p:
-
Particle
- rad:
-
Radiation
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El-Sayed, S.A. Ignition of a Pyrolysis Wooden Particle Based on the Thermal Explosion Theory. Iran J Sci Technol Trans Mech Eng 42, 317–327 (2018). https://doi.org/10.1007/s40997-017-0099-8
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DOI: https://doi.org/10.1007/s40997-017-0099-8