Abstract
Pressure differential systems have the purpose of maintaining tenable conditions in protected spaces for different types of building safe places, like escape routes, firefighting access routes, lobbies, stairwells and refuge areas. The aim of pressure differential systems is to establish airflow paths from protected spaces at high pressure to spaces at lower or ambient pressure, preventing the spread of toxic gas released during a fire. This strategy ought to be supported by a detailed design of the necessary air supply, considering also the cycle of opening and closing doors during the egress phase. The paper deals with the design of a simple pressure differential system intended to be used in a building as a pressurized smokeproof enclosure. Specifically, experimental tests and numerical modelling are conducted with the objective of characterizing the pressure evolution in a small compartment under different conditions and through a cycle of door opening. Experimental tests are conducted in a simple 3-m side cubic enclosure with two doors and no vent openings. While a centrifugal fan blows constant airflow inside the structure, the pressure trend in time is recorded during steady state and transient conditions; additionally, the velocity of the airflow across the doors has been measured by means of an anemometer. Numerical CFD (computational fluid dynamics) simulations are carried out to reproduce the same smokeproof enclosure configuration (both geometrical and boundary conditions) using the fire dynamics simulator (FDS). Furthermore, specific attention is paid to the modelling of the leakage across the doors, directly inserted in the model through a localized HVAC (heating and venting air conditioning) advanced leakage function. Comparisons between experimental tests and numerical simulations are provided. Once the model was correctly calibrated, other geometrical and mechanical configurations have been studied, looking for convenient and efficient positions of the fan in order to fulfill the requirements of the pressure differential, airflow velocity and door handle force. The paper highlights some fundamental aspects on the pressurization and depressurization during steady state and transient phases, trying to identify if there are airflow profiles typical of some geometrical configurations.
Highlights
Life safety is the primary goal for fire engineers, and both active and passive fire protection measures can be adopted to pursue the correct design of the fire safety of buildings
The idea behind these criteria is that after smoke detection, pressurization starts, and the protected space is kept at a given level of overpressure taking into account the leakage across walls, doors and other boundaries letting air flow by cascade towards the accommodation and from there up to the outside of the building through air release paths
Short-term deviations from the suggested minimum design pressure difference might not have a serious effect on the protection provided by a smoke control system
Summary
Life safety is the primary goal for fire engineers, and both active and passive fire protection measures can be adopted to pursue the correct design of the fire safety of buildings. Figure released at continuous passage and leakage (see Figure 1) These systems are mostly used, for instance, instance, to protect the main vertical vertical means means of egress like stairs and fire elevators, or refuge areas, where occupants can wait for help if unable to leave the building independently (hospitals, nursing home, etc.). This kind of system system might might represent represent a good good alternative alternative to the pressurization pressurization of large volumes, such as stairwells, stairwells, because, due to to their their limited limited extension, extension, they they do not require the use of such powerful (and expensive) fans
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
