Study On Somke Temperature And Velocity In The Stairwell With Differnent Opening Conditions

Though high-rise buildings makes our life more comfortable and convenient, it also brings a lot of fire safety problem. Statistical results showed that toxic smoke with high temperature due to incomplete combustion was the most fatal factor to occupant in building fires. As the main occupant passageway in high-rise building, the stairwell should be paid more attention to,thereby, study on smoke movement in the stairwell within high-rise buildings is of great significant for fire safety.Fire smoke movement in the stairwell is much more complex than other simple shaft for its particular structure and the models in previous researchers' work on smoke movement in the stairwell were unsuited to simulate the situation in the high-rise building due to their less floors. In this thesis, considering the condition that the smoke prevention is out of order and the smoke flows into the stairwell, smoke transport characteristics within it is studied by conducting experiments in a one -third scale model. The detailed work include:Using the cell-zone method, an theoretical model was derived for the temperature distribution in the vertical direction in the stairwell on the basis of the conservation equation, considering heat transfer through wall in it, which was validated by performing experiments in the stairwell model mentioned above. In addition, the impact of heat release rate of fire on temperature distribution was discussed qualitatively.A series of experiments were conducted in the stairwell with two openings. The results indicated that, the opening height had a great effect on the smoke movement, namely, the higher the upper opening is, the faster the smoke moves upwards, on the contrary, lowing the opening slows down the spread of smoke. Furthermore, the convection between the stairwell and the environment increased as the rise of the upper opening, which meat that the stack-effect enhanced. The results also showed that the convection velocity grew linearly with the opening height.The location of the fire source is a main effect factor of flow between the stairwell and the environment for the stairwell with uniformly distributed openings. The mass flow rate decreased as the rise of the location of the fire, however the maximum temperature in the stairwell increased gradually. The dimensionless mass flow rate was proportional to the dimensionless fire height, and the dimensionless temperature rise was varied piecewise linearly with height.