Sharif Digital Repository

Smoke is the largest cause of fire related deaths. A smoke control system is an engineered system that modifies smoke movement for the protection of building occupants, firefighters and properties. Unfortunately, in case of fire, stairwells and elevators are frequently filled with smoke, preventing effective evacuation. Many smoke control systems use mechanical fans to control smoke by providing positive pressure at strategic locations. Pressure difference across a barrier can control smoke movement by preventing smoke on the low-pressure side of the barrier from migrating to the high-pressure side. Building designers use codes and rules of thumb to design their building against fire.... 

Suitable design of ventilation systems is one of the strategies to deal with phenomenon like fire in tunnels. For design a ventilation system first should recognize fire and effective parameters on it. So we need a good modeling of fire. Whereas the aim of this research is investigate the critical ventilation velocity, we only studying the effects of fire. Two effective parameter of fire is the rate of heat release and rate of smoke release, therefore with studying physics and nature of fire, obtain these parameters. After calculation of fire effects, we should investigate the effective parameters on critical ventilation velocity. The critical velocity is the air flow that helps prevent... 

Designing of an efficient emergency ventilation system is one of the main approaches to prevent the perilous fire in tunnel phenomenon. For this purpose, firstly, fire behavior and its heat release rate should be investigated. Knowing about temperature distribution and smoke movement is the second step. One of the most considerable factors in smoke control is critical velocity. It means the minimum velocity to prevent backlayering flow. If longitudinal ventilation velocity were less than this amount, smoke and hot gases originated from the fire can enter the upstream zone. This may cause lack of oxygen and decrease visibility for the passengers when they are escaping from the fire field. In... 

Safety against fire and its potential destructions is provided by detection, protection and ventilation methods. Knowledge on fire behavior such as ignition and propagation along with heat and smoke release is essential for implementing these methods. Having such deep information, the fire can be detected at the correct time and be controlled or suppressed, with its heat and smoke removed efficiently, so that rescue services will be enhanced and fatalities and damages will be reduced.Numerical simulation of fire requires deep understanding of multiple phenomena including turbulent flows, conductive, convective and radiative heat transfer, large buoyancy forces, chemical reactions and... 

Cosmology is a knowledge that deals with the matter of creation of the world, its current structure and its end. This scientific field that was a subject discussed by the scientific, philosophical and religious groups has nowadays taken the attention of many scientists and researchers. The philosophers of science, also, are not exemptions from theses groups and cosmology, as a topic common between philosophy and science, is one of the points that are under discussion in the field of philosophy of science. On the other hand, the religions, also, have noticed this issue. Koran that is the most complete divine book sent from God, has taken account of the creation and the Creator as the axis of... 

Fire spread in a road tunnel and its transmission from one vehicle to another was investigated numerically in this study. FDS was used as an open-source, free CFD software. Two boxes close to the car’s dimensions were modeled in a 40m long tunnel and fire transmission from one to another was considered. Ignition temperature was assigned to the second box’s surface as the condition for its ignition start and longitudinal ventilation was applied to the tunnel. At each case, ignition time of the second box was captured. Effects of ventilation velocity, HRR, distance, tunnel height and slope of the tunnel parameters were considered on the ignition time of the second box. Moreoveras a case study,... 

In this study pollution generated by a electronic cigarette in a bus is observed. Resultant smoke from these products consist of different components which may endanger health and one should make sure them amount in general transport vehicles like bus are in permissible limit. These components are initially in liquid shape and evaporate. Tracking liquid particles are done with the aim of Lagrangian approach. For this the geometry is generated at first. Then structured mesh was generated with ICEM CFD which is a powerful mesher. Different conditions of smoking source and bus doors were studies and results were compared.Change of pollutant concentrations is strictly depend on position of... 

The fire event may cause danger to life and property. In general, most fire-detection devices are set on the wall or ceiling. . However, this method is not flexible enough to detect a fire occurrence, and this needs the use of many fire-detection devices in a building. Since it is not suitable, we use an active fire-detection device to detect a fire incident. In the past, smoke sensors were used for fire detection, but often the smoke sensors triggered a false alarm when someone smoked in the room. Therefore, multisensor fire-detection methods are one of the current important developments for fire- detection technology. We design a fire-detection module using an ionization smoke sensor... 

When a fire breaks out in a tunnel, due to the enclosure of the interior of the road tunnels, hot and poison smoke quickly spreads in the tunnel. This phenomenon, in addition to destroy the tunnel structure, causes a lot of financial and human losses. In recent years, research into fire control has become more important with the occurrence of numerous accidents in road tunnels and fatalities. Longitudinal ventilation is still the main method for controlling smoke distribution in tunnels due to lower construction costs and acceptable efficiency. Numerous studies have been conducted to investigate the effect of different and effective parameters on fire control and smoke emissions in direct... 

With the process of achieving a higher state of social development and technological advances, the need for higher and more strict safety standards has been increased. In this regard, it is of great importance to have an accurate understanding of the fire phenomena and its consequences. Among the adverse effects of fire, a significant percentage of the fire fatalities is related to the fire-induced buoyant gases (smoke) flow which can lead to suffocation. Therefore, it is necessary to know the physics of the fire phenomena well. In fire investigation methods, the numerical study is an appropriate choice, because of the lower executive cost (relative to the experimental study) and the wider... 

Tehran air quality is facing a real crisis. Reports of pertinent organizations show air quality is deteriorating in recent years and unhealthy days are increasing. As a result, study and planning in order to change this trend and moving toward improving air quality is a necessity. On the other hand, in order to make proper decisions and choosing effective approaches considering cost-effective attribute and legal, temporal and budget restrictions, selecting the right tool is essential. Air quality models are the tools which in a cost saving manner and reasonable time can provide the required results for researchers, decision makers and legislators. An applicable model correspondent with urban...