Experimental and numerical study on pyrolysis and autoignition of OSB exposed to radiant heat fluxes

doi:10.16265/j.cnki.issn1003-3033.2022.03.019

Abstract

Abstract:

In order to predict autoignition time of OSB exposed to radiant heat fluxes, firstly, milligram-scale thermogravimetric analysis(TGA) tests were conducted to parameterize the established pyrolysis model by model fitting method. Subsequently, gram-scale autoignition experiments, using seven predesigned constant heat fluxes, were implemented in a cone heating apparatus. Then, inversion model of OSB thermodynamic parameters was established by combining an improved numerical model and measured surface temperatures and mass loss rates to determine thermal conductivity and specific heat of OSB. The results show that the ignition time predicted by critical temperature and critical mass loss rate are 194, 116, 67, 47, 24, 16, and 129, 103, 59, 42, 27, 20 s respectively under six constant heat flows (28, 30, 35, 40, 45 and 50 kW/m²).

Key words: radiant heat fluxes, oriented strand board (OSB), spontaneous ignition test, numerical model, thermodynamic parameter, ignition time

FENG Quan, ZHANG Mingrui, GONG Junhui. Experimental and numerical study on pyrolysis and autoignition of OSB exposed to radiant heat fluxes[J]. China Safety Science Journal, 2022, 32(3): 137-143.

Figures/Tables 10

Fig.1

Fig.2

Tab.1

Tab.2

Thermal parameters of OSB and ceramic fibers

物质/ 组分		参数	值			数据源
OSB		ρ/(g·m^-3)	5.48×10⁵			试验
		ε	0.850			文献[13]
		ΔH/(J·g^-1)	200			文献[14]
炭		k_c/(W·m^-1·K^-1)	0.08-3.93×10^-5T			文献[1]
		C_p,c/(J·g^-1·K^-1)	1.39+3.6×10^-4T			文献[1]
		ΔH_c/(J·g^-1)	-3770			文献[15]
灰分		k_a/(W·m^-1·K^-1)	0.058			文献[15]
灰分		C_p,a/(J·g^-1·K^-1)	1.244			文献[15]
物质/ 组分	参数			值	数据源
水	k_w/(W·m^-1·K^-1)			0.658	文献[16]
	$C p, w$ /(J·g^-1·K^-1)			4.200	文献[17]
	ΔH_w/(J·g^-1)			2 400	文献[18]
陶瓷纤维	k_f/(W·m^-1·K^-1)			0.060	制造商
	ρ_f/(g·m^-3)			4.0×10⁵	制造商
	C_p,f/(J·g^-1·K^-1)			0.670	制造商

Tab.2

Fig.3

Tab.3

Tab.4

Fig.4

Tab.5

Critical surface temperatures and critical mass loss rates of OSB at different constant heat flow

热流/ (kW·m^-2)	T_c/K	误差	$m ″ · c$ / (g·m^-2·s^-1)	误差
28	756.4	70.9	8.42	2.17
30	711.7	20.6	8.82	1.39
35	701.3	42.8	7.42	1.78
40	705. 7	12.0	7.82	0.77
45	660.7	4.9	5.35	1.22
50	647.0	18.5	4.81	1.39

Tab.5

Fig.5

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序号	反应	A /s^-1	E_a /(J·mol^-1)	n	T_p /K
1	水→水蒸气	4.4×10⁷	5.81×10⁴	1.60	346
2	OSB→0.01 OSB残炭1+0.99 OSB气体1	1.3×10⁶	9.68×10⁴	1.00	603
3	OSB残炭1→0.02 OSB残炭2+0.98 OSB气体2	4.0×10⁹	1.43×10⁵	0.73	638
4	OSB残炭2→0.33炭 +0.67 OSB气体3	8.5×10⁵	9.60×10⁴	3.40	672

参数	优化结果	文献来源
参数	优化结果	文献[1]	文献[11]	文献[12]
k/(W·m^-1·K^-1)	0.05+6.00×10^-4T	0.056+2.6×10^-4T	0.106	0.08+1.0×10^-4exp(-0.21T)
C_p/(J·g^-1·K^-1)	3.51-4.45×10^-3T	1.5+1.0×10^-3T	0.700	0.73+2.5×10^-3T

参数	OSB残炭1	OSB残炭2
k/(W·m^-1·K^-1)	0.11+1.2×10^-4T	0.11+1.3×10^-4T
C_p/(J·g^-1·K^-1)	1.20+1.5×10^-4T	0.14+1.0×10^-4T