カテゴリー Ⅱ 日本建築学会環境系論文集第 8 巻第 71 号,35-313,215 年 4 月 J. Environ. Eng., AIJ, Vol. 8 No. 71, 35-313, Apr., 215 軒下部に衝突する火炎の熱伝達特性 HEAT TRANSFER TO AN EAVE DURING FLAME IMPINGEMENT 樋本圭佑 1 2, 出口嘉一 Keisuke HIMOTO and Yoshikazu DEGUCHI A series of model experiment was conducted for evaluating heat transfer to a non-flammable eave during flame impingement. Excess temperature T and incident heat flux to the eave q were measured under sixteen experimental runs with varying parameters of eave section geometry, burner geometry, installation position of the burner, and fuel supply rate. In order to correlate the imum excess temperature T, a reference length scale L was deduced from the governing dimensionless parameter Q. Dimensional analysis of thermal structure of the flow showed that the imum excess temperature T is expected to be proportional to x H L in the flaming regime, and x H L 1 in the non-flaming regime. The agreement with the experimental data was reasonable for all the tested eave sections and burner geometries. Keywords: Historic Urban Area, Model Experiment, Fire Spread, Heat Transfer, Eave 1)-6) 7) 2 8) 9), 1) 1 16 1 2 独立行政法人建築研究所博士 ( 工学 ) 竹中工務店技術研究所博士 ( 工学 ) Building Research Institute, Dr.Eng. Research & Development Institute, Takenaka Corporation, Dr.Eng. 35
(mm) (mm) H (mm) mf L/ 1 4 2., 6., 1. 2 2 1., 2., 6. A 3 4 2., 6., 1. 4 2 1., 2., 6. 69 5 4 5., 11.5, 18. 6 2 5., 11.5 1 2 4 B 7 4 5., 11.5, 18. 8 2 5., 11.5 x=y= z= 9 2., 6., 1. A 3 9mm 1 2., 6., 1. 11 5., 11.5, 18. 9mmz B 12 5., 11.5, 18. 4 13 2., 6., 1. 4,mmx 4mmy A 14 4 2., 6., 1. 149 (1) 15 () 5., 11.5, 18. B 16 5., 11.5, 18. 69mm (2) (3) 4/1 3 A 1mm1mmB 1mm4mm 2 3 x x y (1) (2) 2 4 B H (1) 2mm (2) 4mm 2 m f 16 2 3 m f m f x=5mm m f 1.~18. L/ Q m f 91.26kJ/L 1 m f 36
(1) (2) (3) x= x T K =3.2mm 1 2 52 y=mm C x=mm2mm 4mm6mm1,mm1,4mm y=-14mm W14mm E 2s m f 1 3 T q H m f 2. L / m f 1. L / H L fl, x x L fl q CAPTEC CAPTHERM 1 2 6 y=mm x=1mm3mm5mm8mm1,2mm 1,7mm 2s 3 L fl m f H L fl, x L fl L fl.3s 3s 1 3s L fl, C L fl, I L fl, M 5 1 L fl, M 8~82mm H L fl, M L fl, M H.42.78 L fl 1) 1 2 5 2 Q cpt g B QB 1 2 3 2 Q cpt g B Q Q c P (1) T g B L, QB 6 fl M 6 11), 12) A QB 1 B Q 1 B Q A -57.8%+37.5% B -14.3%+4.5% x A H=4mm m =1. L/ 1913 B f 37
7 z=5mm T Cy=mm 6 Ey=14mm Wy=-14mm 3 x=mm C C E W E W T C 5mm E W 7) ECW W T B m f =11.5 L/ 567 8 z=5mm T x=mm T x=4mmx=1,mm E W T C 1 7(a) T C T T x=4mm 6mm 7 y x T T x 1) 38
T 16.9 5.38 3 3 Q 2 H 5 r H.18 3 3 2 3 Q 2 H 5 r H r H.18 T r (2) T, 2 3 5 3 T, Q H (3) z A T T z Q 2 3 z Q c T gz Az 2 3 P (2) (4) (3)(4) 2 z H Az H (5) 13) T T T H, r T H r, 2 3, TQH f r H (6) f QH (7) 1 2 5 2 QH Q cpt g H (6) 1) 1) 2) z H Az H 2 3) (6) r H H 1)3) L (6) T T f x H L (8) T L (1) y (1) 2 B L (9) QL Q cp 1 2 3 2 T g L 1 L 2 Q c T g 1 2 3 P (1) L (8) f y 2 x z z u w x z (11) 1 p gt z (12) 2 ut wt k T q x z c 2 z (13) P c P u w x z p k q z d dx udx lim w C (11 ) z 1 lim p gtdz (12 ) z d dx 1 utdz c P q C q dz (13 ) C q C (11 ) 1 14) 2) u T x u T b u u u z b T T z b T (14) (11 )~(13 ) d dx bu u d C (11 ) 1 lim p g bt T d z d dx bu T (12 ) 1 u T d q C q dz (13 ) cp 39
(12 ) 1 (13 ) 1 2 lim p z 2 u (15) q C St cpu T (16) 1 R H F q dz C (17) St H F R b u T x l b x u x m n T x (18) (11 )~(13 ) x (13 ) 2 1 2 St 8) l m n 2 3 b x 1 3 u x T x b x u x (19) -1 T x 1~8 (8) 9(a) T T x H L (19) 2.5 T 2 7.22 x H L T 1 1.5 x H L x H L 1.7 x H 5. x H 1.7 L 5. L (2) T T x H L -2 x H L =1.7 x H L =5. x H L.68 2.25 1.19~4.22 2.3~27.9 (2) 9(a)x H L x H L 15) T T x x.375q B. 75 L (21) 3) 1(a) 1~8 9~12 13~16 9(b)9(c) y 2.5 T 12.3 T 1.37 2.5 T 7.22 T 2.57 x H L 3 x H L 1.7 x H 1.5 x H L 4.5 x H x H L 2 x H L 1.7 x H 1 x H L 3. x H 1.7 L 4.5 L 1.7 L 3. L (22) (23) x H L -3 x H L -1.5 x H L =5. x H L =3. x H L x x.3q B. 3 L (24) 1(b) (21) x 1(c) q T (8) q f x H L (25) 11(a)~(c) q x H L 31
T 4 1. 61 36.1 x H L q (26) 2. 13 65.4x H L q (27) 1. 66 34.x H L q (28) 311
q T y=mm C q T q x H L T x H L -1 x H L L T q JSPS 2436248 B [m] b [m] cp [kj/kgk] D [m] g [m/s 2 ] H [m] H F [kj/kg] k [kw/mk] L [m] L fl [m] L fl, x [m] m f [L/] p [Pa] Q [kw] Q [kw/m] Q q [kw/m 3 ] q [kw/m 2 ] q C [kw/m 2 ] St T [K] T [K] T [K] u x [m/s] u x [m/s] w z [m/s] x [m] x [m] [1/K] [kg/m 3 ] R 1) Alpert R.L., Calculation of response time of ceiling-mounted fire detectors, Fire Technology, Vol.8, No.3, pp.181-195, 1972 2) You H.Z., Faeth G.M., Ceiling heat transfer during fire plume and fire impingement, Fire and Materials, Vol.3, No.3, pp.14-147, 1979 3) Kokkala M.A., Experimental study of heat transfer to ceiling from an impinging diffusion flame, Fire Safety Science, Proc. 3rd Int l Symp., pp.261-27, 1991 4) Heskestad G., Hamada T., Ceiling jets of strong fire plumes, Fire Safety Journal, Vol.21, pp.69-82, 1993 5) No.484pp.149-156 1996.6 6) No.55pp.1-621.12 7) Hinkley P.L., Wraight H.G.H, Theobald C.R., The contribution of flames under ceilings to fire spread in compartments, Fire Safety Journal, Vol.7, pp.227-242, 1984 8) Delichatsios A.D., The flow of fire gases under a beamed ceiling, Combustion and Flame, Vol.41, pp.1-1, 1981 9) Sugawa O. Simple estimation model on ceiling temperature and velocity of fire induced flow under ceiling. Fire Science and Technology, Vol.21, No.1, pp.57-67, 21 1) Oka Y., Ando M. Temperature and velocity properties of a ceiling jet impinging on an unconfined inclined ceiling, Fire Safety Journal, Vol.55, pp.97-15, 213 11) Zukoski E.E., Kubota T., Cetegen B., Entrainment in Fire Plumes, Fire Safety Journal, Vol.3, pp.17-121, 198/1981 12) Yuan L.M., Cox, G., An experimental study of some line fires, Fire Safety Journal, Vol.27, pp.123-139, 1996 13) 22.1 14) Turner J.S., Buoyancy effects in fluids, Cambridge University Press, 1973 15) Heskestad G., Virtual origin of fire plumes, Fire Safety Journal, Vol.5, pp.19-114, 1983 1) 3 2) 13).6~.48 1 3) 15) x T x H E C W T x H T x T T x 312
HEAT TRANSFER TO AN EAVE DURING FLAME IMPINGEMENT Keisuke HIMOTO 1 and Yoshikazu DEGUCHI 2 1 Building Research Institute, Dr.Eng. 2 Research & Development Institute, Takenaka Corporation, Dr.Eng. A series of model experiment was conducted for evaluating heat transfer to a non-flammable eave during flame impingement. Excess temperature under an eave T, and incident heat flux to the eave q, were measured under sixteen experimental runs with varying parameters of eave section geometry, burner geometry, installation position of the burner, and fuel supply rate. Experimental results showed that diffusion of the impinged flame/plume progresses as it flows along the eave. However, in some cases, its distribution in width direction was not uniform such that the excess temperature in the center was lower than the excess temperature near the side wall as the impinged flow was attached to the side wall. Thus, in this study, the imum excess temperature in the plane perpendicular to the main flow direction T was selected as the reference excess temperature for evaluating the change of thermal behavior. Thermal behavior of a flame/plume impinged to an eave is similar to that of a flame/plume impinged to a ceiling. Thus, for the modeling of thermal behavior of a flame/plume impinged to an eave, there was a possibility of adopting the modeling approach similar to that of a flame/plume impinged to a ceiling. An existing model for the ceiling jet which is widely used in fire safety design of buildings normalizes a length from the impingement point x by the ceiling height H. However, applicability of this model to the present experimental result was not satisfactory as was expected. Major reasons for this are: (1) the ceiling model is deduced from the weak plume theory and is not applicable to the flow which involves flaming; (2) the ceiling model does not assume restriction of the impinged flow in the horizontal direction such as an eave does; and (3) there is no rationality of adopting the eave height or ceiling height H as an normalizing length scale in a model which assumes the impingement point as the virtual heat source. Based on these, a reference length scale L was deduced from the governing dimensionless parameter Q and was used in place of the eave height H. The present experimental result was well correlated with the new dimensionless length parameter x H L. Dimensional analysis of thermal structure of the flow showed that the imum excess temperature T is expected to be proportional to x H L in the flaming regime, and x H L 1 in the non-flaming regime. This estimate was verified with the present experimental result for all the tested eave sections and burner geometries. Even better agreements were obtained by adjusting x H L based on the virtual heat source assumption. Incident heat flux to the eave q was also correlated with x H L with reasonable accuracy, though the transition of behavior with regard to the transition of regime was not as clear as that of T. This is because the intensity of thermal radiation heat transfer is proportional to the heat source temperature to the power of four, and the transition of regime is less influential on the behavior transition of q. The present experiment was conducted using diffusion flame burners placed on the horizontal floor as the heat source, and does not replicate the actual window flame that impinges to an eave. However, the reasonableness of the new dimensionless length parameter x H L for this specific experimental condition indicates that thermal behavior of an actual window flame impinged to an eave can also be correlated with the similar approach as long as a length scale L is selected adequately. (214 年 8 月 21 日原稿受理,215 年 1 月 14 日採用決定 ) 313