Experimental Study on the Branching of Flow throngh T-Shaped Corridor
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概要
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The objective of this experimental study is to characterize the flow behaviours and to estimate the coefficients of head loss (F ) and heat loss (ΔQ ) when the fire products flow were divided at the branching part in the T-shaped full scale corridor. The wood crib pile as a model fire source was set at 4m apart from the closed end of the main corridor. The vertical (Y-axis) profiles of velocity (V ), temperature (T ), optical smoke density (Cs ) and gas concentration (Cg ), were measured along the corridor (X-axis). The ignition system, measuring system of aforesaid quantities were the same as the ones in the previous report.1)Following results were obtained; (1) Main flow from the starting line to branching part (expressed suffix i =1) was divided into two flows, i.e. maintained flow (i =2) and branched flow (i =3) at the branching part. The ratio of the flow thickness (δvi ) and width (Bi ), δvi /Bi ≈0.1«1 were estimated and so those value implied that the flow can be taken as a shallow flow. δv1 ≅δv2 ≅0.3m and δv3 ≅0.2m were observed, and the ratio of δv3 /δv1 ≅0.7 was observed as independent of time. (2) Rankin's and Taylor's relations were also estimated tobe equally conserved in both corridor as Vavi /√θi ·δvi ≈0.14 and as Vi /Qi1/3 ≅0.2 independent of time. (3) As for the flow in the early stage of the penetration, its Reynolds number Re is less than 3000, Richardson number Ri ≈0 and Archimedes number Ar ≈1. This means that in the estuary stage the situation of the penetrated flow is critical with large Cf , very unstable free surface and considerable heat loss. However, when the flow is developed, Re exceeds 3000, Ri > 0 and Ar > 1. (4) The estimation on the head loss (F ) and heat loss (ΔQ ) of branching have been pursued on the basis of Bernoulli's equation and the heat balance. The attenuation coefficient Ω and χ for the head loss and heat loss can beexpressed by equation (1)Ω = F⁄ 1⁄2Vav 2·(1+Ar ) ≡ Kv· Lv ⁄δv , χ = ΔQ ⁄ρ·Cp·Tav·Vav ≡ KT ·LT ⁄δv , (1)where Lv and LT are the equivalent length for the head loss and heat loss regarding the penetrated flow.
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