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A Model Of Smoke Movement In Stair Shafts

Nii, D., Takeichi, N., Harada, K., Ohmiya, Yoshifumi, Yamana, Toshio and Hagiwara, I., 2004. A Model Of Smoke Movement In Stair Shafts. AOFST 6


Full-scale experiments were carried out to measure temperature and smoke concentration distribution in order to develop prediction model for movement of smoke caused by fire in stair shaft. Smoke arrival time, transient changes of profiles and steady state profiles were determined by using measured data. In case of no opening above fire source, smoke rose up mainly at center part of shaft as mixing with air. While, in case of door opened above fire source, uni-directional upward flow was observed due to buoyancy forces. Prediction model for smoke movement and temperature distribution was developed and compared with experimental results. In landing with fire source, two-layered approximation was applied. Upper part of shaft was approximated by a duct with ribs which increases flow resistance. In case with no opening above fire source, it was approximated that smoke rose up by mixing with upper air due to turbulent diffusion. Turbulent mass flux was expressed with density gradient and turbulent diffusion coefficient. In case of door opened above fire source, vertical temperature distribution was approximated by an exponential function derived from heat and mass balance, and smoke velocity was predicted by flow resistance of stair shaft. Calculation values of temperature and rising velocity agreed fairly well with experimental results.

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