Environmental Wind Under Natural Smoke Vent Smoke Flow Study

Smoke has been found to be the biggest factor of death in fire accidents. The smoke state indoor is decided by the mass flow rate which flow the exhaust vent while using natural smoke exhaust. Up till now, the research on natural smoke exhaust is usually in no-wind conditions, and most of the research is mainly relation to the regularity of smoke spread sindoor. Factually, building on fire is always surrounded by the wind. But now at home and abroad, the research on smoke flows of natural smoke exhaust vent is nearly a blank. In this paper, the smoke flow of natural exhaust vent under horizontal environmental wind in the building is studied with the use of theoretical analysis and numerical simulation. The main job is done as follows:(1) Under the conbined pressure of wind and hot, the model of gas-mass rate in natural exhaust vent is proposed and the theoretical calculation method on the height and temperature of smoke layer is given in the mean time;(2) When the natural exhaust vent is over fire, the caculation method of the gas-mass rate is given through numerical simulation-, when the natural exhaust vent is at a certain distance away from the center of the fire, the regular theoretical model can be applied well and the range of the distance is analysed.(3) The effect of environmental wind on natural smoke exhaust is evaluated with total wind pressure coefficent which is the wind coefficient difference between inlet and exhaust vent of the building. The simulation result indicated:when the coefficient is positive, the faster the wind, the better the smoke exhaust; when the ecofficient is negative, the natural smoke exhaust will be inhibited.(4) An expression is given about the critical wind velocity of invalidation at which the natural smoke exhaust is just losing its function under the negative coefficent. The reference to the design of natural smoke exhaust system can be provided with the combination of the local wind speed. The fire source and surrounding conditions are different from each other under actual fire. Therefore, configuration of smoke management system of a building should accord with the demand of the building. According to this point, the work of this thesis is helpful to design of smoke management system of a building for its model and data reference.