Ventilation and heat and smoke extraction from industrial buildings

Abstract

The flow into and out of industrial buildings and therefore the ventilation, the heat and smoke extraction in case of a fire or at certain industrial manufacturing processes is strongly influenced by the pressure field established in the wind flow around the building. Information about the wall pressures of buildings under the action of wind are presented in building codes. Usually, these data are related to the wind loading only and are based on worst case considerations for simple building shapes. For the ventilation of a building, however, detailed flow field information are necessary because the venting performance depends strongly on the local flow situation. The venting can be executed either naturally by buoyancy forces or mechanically by exhausting systems. Especially vent systems working by buoyancy forces are very sensitive to the wind action. This should be taken into account when designing such vents. The usual practice is to investigate the vents under cross-wind condition. The testing procedure corresponds to an isolated vent in an infinite flat roof and the venting characteristics calculated on the basis of those test results do not take care of all the other important influence parameters like building geometry, local wind flow situation, interference with other buildings, etc. A further important effect is due to the wind flow into the building. For natural venting systems the inflow is coupled automatically with the outflow, which is directly related to the heat generation in the building. For mechanical exhausting systems, however, this coupling does not exist. Therefore, the air in the space to be vented may mix with fresh air due to the jet flow discharged by the inflow openings. This paper gives a survey of the problem of venting, wind action and vent design illustrated by some typical examples.