Influence of Density and Moisture Content on Heat Release Properties of Wood

Transcription

1 Original Article *1 Influence of Density and Moisture Content on Heat Release Properties of Wood Shinichi KIKUCHI Masayuki KAWARASAKI The building standard law of Japan was revised in 1998 and the test method for evaluating fire prevention materials was changed from the conventional surface flammability test to the heat release test. This is because the heat release property is the key factor in characterizing the flammability of building materials. To develop fire prevention materials corresponding to various wood materials, it is necessary to clarify the heat release properties of wood. To accomplish this, heat release tests were carried out on six species using the ISO cone calorimeter. The species tested were Pinus densiflora, Larix leptolepis, Chamaecyparis obtusa, Cryptomeria japonica, Abies sachalinensis and Fraxinus mandshurica. The specimens were heated at an irradiance level of 5 kw/m 2, heat release rate, total heat release and effective heat of combustion were measured. Wood had a higher first peak heat release rate just after ignition and high second peak, when the back of the specimen began to burn. After flaming combustion ceased, glowing combustion of the carbonized layer continued for a long time. Heat release rate in the flaming period was related to the original moisture content of the wood. There were clear differences in the total heat release of specimens between the conifers and, and these increased linearly with density. The effective heat of combustion on a dry basis was MJ/kg in the flaming period, and MJ/kg in the glowing one. Key words: heat release, effective heat of combustion, cone calorimeter 1998 ISO 6 5kW/m MJ/kg 2933MJ/kg

2 Influence of Density and Moisture Content on Heat Release Properties of Wood Pinus densiflora Larix leptolepis Chamaecyparis obtusa Cryptomeria japonica Abies sachalinensis Fraxinus mandshurica 5 1 1T 1L 15 1 R mm 23 5%RH 3 I FPL 2 OSU ASTM E 96 3 JIS A II 9% 5% ASTM E ISO Table 1. Materials used for heat release experiments. Seasoning Species Number of Density Mark condition specimens (g/cm 3 ) P. densiflora L. leptolepis C. obtusa %RH C. japonica A. sachalinensis C. obtusa hr C. japonica J. Hokkaido For. Prod. Res. Inst. Vol.22, No.2, 28 2

3 2.2 ISO µm 12mm 65kg/m 3 Heat release rate 9494mm 時間 (min) 5kW/m 2 Time 4 12 THR 1 Medtherm Model. GTW A WL ZAJ % 時間 (min) Time 1 5kW/m 2 I 3. Fig. 1. Heat release rate, total heat release and weight loss 3.1 of A. sachalinensis and at 5 kw/m 2 irradiance (Condition I). I THR WL note) THR: Total heat release, WL: Weight loss. 1 Heat release rate 発熱速度 (kw/m 2 ) 発熱速度 (kw/m 2 ) 1 2 FLAME_T FLAME_T 1 COM_T F_THR 2 2 I COM_T 3 F_THR 4 2 COM_TF_THR 5 2 COM_T F_THR COM_T F_THR COM_T 2 46kW/m kW/m A. sachalinensis THR WL Total heat release Total heat release 総発熱量 (MJ/m 2 ) 総発熱量 (MJ/m 2 ) Weight loss 質量減少量 (g) Weight loss 質量減少量 (g)

4 Influence of Density and Moisture Content on Heat Release Properties of Wood Heat release rate kw/m COM_T F_THR 6 3 Fig. 3. Relation between density and flaming period. 1 COM_T 2 Legend),,,,, : See Table 1. Note) COM_T: See Fig. 2. y = 161x -.2 Conifer R 2 =.946 y = 142x -.5 R 2 = min FLAME_T Time g/cm 3 Density 2 Fig. 2. Flaming period and total heat release in the 4 flaming period. Fig. 4. Relation between density and total heat release in FLAME_T COM_T F_THR the flaming period. Note) FLAME_T: End time of flaming combustion, COM_T: Flaming 1 period, F_THR: Total heat release in the flaming period. F_THR 2 Legend),,,,, : See Table 1. Note) F_THR: See Fig. 2. COM_T s y = 845x Conifer R 2 =.64 y = 579x R 2 = g/cm 3 Density F_THR MJ/m 2 COM_T s 5 Fig. 5. Relation between density and flaming period of specimens conditioned at I or II. III 1 COM_T 2 Legend) I, II,,,,,, : See Table 1. Note) COM_T: See Fig % COM_T 1% ISO 566 2% F_THR F_THR 9% 5% 5 COM_T Conifer g/cm 3 Density J. Hokkaido For. Prod. Res. Inst. Vol.22, No.2, 28 4

5 MJ/kg 15.2MJ/kg 14MJ/kg hc_wethc_wet hc_dry hc_glow 2 hc_wet = F_THR FLAME_T までの質量減少量 hc_dry = hc_wet.91 または.95 hc_glow = 2_THR-F_THR 2 分間の質量減少量 - FLAME_T までの質量減少量.91 I.95 II hc_glow 29 33MJ/kg MJ/kg 16 FLAME_T 2_THR2 hc_wet hc_dry 4. hc_dry Table 2. Effective heat of combustion. Seasoning Species Species condition Effective heat of combustion (MJ/kg) hc_wet 1) hc_dry 2) hc_glow 3) P. densiflora L. leptolepis C. obtusa 5%RH C. japonica A. sachalinensis C. obtusa hr C. japonica note) 1) Effective heat of combustion in the flaming period (wet base), 2) Effective heat of combustion in the flaming period (dry base), 3) Effective heat of combustion in the glowing period. 1416MJ/kg 29 33MJ/kg 1Babrauskas, V., Peacock, R. D.: Fire Safety Journal 18 (3), (1992). 2Brenden, J. J.: Journal of Fire and Flammability 6 (1), 5-64 (1975). 3ASTM E 96-83: "Standard test method for heat and visible smoke release rates for materials and products.", Brenden, J. J.: Journal of Fire and Flammability 6 (3), (1975)

6 Influence of Density and Moisture Content on Heat Release Properties of Wood 5Smith, E. E.: Journal of Fire and Flammability 8 (3), (1977). 6Babrauskas, V.: Fire and Materials 8 (2), (1984). 7ASTM E : "Standard test method for heat and visible smoke release rates for materials and products using an oxygen consumption calorimeter.", ISO 566-1: "Reaction to fire tests - Heat release, smoke production and mass loss rate - Part 1: Heat release rate (cone calorimeter method)", 22. 9Janssens, M.: Fire Safety Journal 17 (3), (1991). 1Tran, H. C.: "Heat Release in Fires", Babrauskas, V., Grayson, S. K. ed., Elsevier Science Publishers LTD, London, 1992, pp JIS A Hugi, E., Wuersch, M., Risi, W., Wakiki, K. G.: J. Wood Science 53, (27). 14White, R. H.: Wood and Fiber Science 19 (4), (1987). 15Fangrat, J., Hasemi, Y., Yoshida, M., Kikuchi, S.: Fire and Materials 22 (1), 1-6 (1998) * J. Hokkaido For. Prod. Res. Inst. Vol.22, No.2, 28 6