Wind Effect on Flame Characteristics & Heat Movement in Compartment - Literature review Example

Wind Effect on Flame Characteristics & Heat Movement in Compartment [Name] [Institutional] [Date] Table of Contents Literature Review 3 Experimental Research on Compartment Fire 3 Influence of relative location of two opening on fires & smoke behaviors in a stairwell with a compartment 3 Effect of Fire Fighting on a Fully Developed Compartment Fire 6 Numerical Investigation into Compartment Fire 9 References 11 Literature Review This research contains a literature review on various subjects about the effect of wind on the flame characteristics and the movement of heat in a compartment. The research covers literature on compartment fires in terms of the influence of relative location of any two openings on smoke and fires behaviors in a case of a stairwell that has a compartment and the effect of fire fighting in a place where compartment fire is fully developed. Further, the research examines literature on the numerical investigation on the subject of compartment fire. Experimental Research on Compartment Fire Influence of relative location of two opening on fires & smoke behaviors in a stairwell with a compartment According to Goo (2012), any active fire safety measure put in place, for example automated fire sensors and notification systems, controlled smoke detection systems or automatic systems for fire and smoke suppression are very critical in the role of managing fire and smoke in case of a compartmental fire in a building. The above mentioned systems should be given utmost consideration in all buildings during construction. Management of fire emergency systems, which ranges from the strategic architectural design of the building for fire management and fire emergency components such as fire exit doors and fire extinguishing material, also plays a great role in managing a fire emergency. Stairwells are vertical shafts with doors connecting them to the main building compartments in high rise buildings. They are extensions which generally create space for the staircase and also are very useful when it comes to emergency escape/exit incase of fire and also assist greatly in fire fighting. The openings in stairwells affect adversely smoke and fire behaviors in in-building fires especially in connected compartments of tall buildings due to pressure differential between the main building and the stairwell (Li, Cheng, Cui, Dong & Mei, 2013). In a fire scenario fire mainly starts up in the main building thus the stairwell being left out which is advantageous to fire fighters and people trapped in the buildings as they can easily escape through the stairwell. Compartments which are generally building sections with limited space and enclosed by walls and doors limit fire and smoke spread in the whole building. However there emerges a great problem due to the pressure difference between the stairwell and the main building. In general physics hot air has a higher pressure than cold air. This is due to charging of air molecules by the heat which gives them the tendency of moving vigorously. In our stairwell case air in the stairwell remains on normal conditions while the air in the building compartment is heated up and has a higher pressure. Hot air which mainly comprises of smoke moves to low pressure areas by spreading out of the compartment (Lu, Hu, Delichatsios, Tang, Qiu & He, 2015). As the air cools down, it moves down the designated smoke relieving outlets which are stairwells and shafts. Smoke which is mainly the component of air in a room on fire tends to move from high pressure to low pressure. This means that smoke will move from the building compartment into the stairwell and this may have catastrophic effects on fire fighting. Stairwell extensions can also be subjected to a high pressure to deviate smoke from getting into them as these lobbies sometimes serve as refuge areas for fire survivors and fire fighters and they should be kept safe from smoke. It is highly recommended that high pressure be applied on the stairwells; this is to maintain a pressure balance between the fire invaded areas and the relatively low pressure stairwell. This is attained by using separate pressurizing systems which generally balances the pressures. Fire burns more in well ventilated areas mainly due to oxygen flow which is the main factor in combustion. Ideally the burning compartment runs low on oxygen as the fire grows and so fire the fire burns out into the stairwell where there is plenty of oxygen to support its burning. The high pressure smoke can easily flow through building interconnections if there is no suppressing system put in place. This can lead to a lot of smoke flowing into the corridors and stairwells if the entrances are not firmly closed. Expansion of heated air brings about a lot of pressure which can force open doors if not firmly closed (Wu, 2010). Openings on the stairwell come in handy in helping relieve the stairwell of smoke. This is done by allowing smoke flow out of the burning compartment into the low pressure stairwell area where due to pressure difference between the stairwell and the outside the smoke is able to flow out. Generally openings in a fire scenario tend to balance pressure between the outside and the inside which helps keep the conditions of a burning compartment more or less same as the conditions outside. They also help in managing of combustion in a burning compartment to prevent back draft. Alarifi et. al. (2014) asserts that a back draft is an occurrence where oxygen is re-introduced into an otherwise gas-phase combustion which leads to a rapid ignition which sometimes comes in form of an explosion. These posses a great threat to fire fighters and must be prevented at all costs. A hole on the highest point of a room provides adequate ventilation which allows heat and the hot gases (smoke) to escape .this brings about a somehow cooling effect to the burning compartment and prevents further combustion of hot gases and the possibility of a backdraft occurrence. Effect of Fire Fighting on a Fully Developed Compartment Fire Flame/fire extinction is where a fire or combustion is brought to a stop prematurely by suppressing one or even more of the necessary conditions which are necessary for combustion to take place. Extinguishing a flame has great relation with incomplete material combustion as in both cases there is presence of potentially combustible material which would otherwise have burned to completion under normal circumstances (Alarifi et. al., 2014). This is the case in fire fighting where the normal conditions for combustion are interrupted in the act of putting out fire either by pouring water or using nitrogen. This leads to production of partly burnt hydrocarbon gases, hydrogenous gases and carbon monoxide. If the percentage of the oxygen gas in a compartmental fire incident falls below a certain point it leads to presence of partly combusted substances. This can be attributed to the flame being put off when it is at different stages of combustion depending on the flammability of the materials. The mechanism involved in putting off a flame is believed one of the main factors leading to massive emition of carbon monoxide from fires. In poorly ventilated compartments, fire extinction brings about emitions of readily combustible fuel mass in form of gases leaking out through the ceiling. These readily combustible gases can also react with the low percentage of oxygen present in the compartment depending on the current temperatures of the compartment. Similarly in poor ventilation conditions, choking out a flame results to a large air mass being channeled to the ceiling which is made of potentially a highly combustible material. With consideration to the temperatures in the ceiling (i.e. above 200% c), the little amounts of oxygen leaking through the ceiling can readily react with the residual gases from partly burnt fuels leading to carbon monoxide formation. However carbon monoxide and hydrocarbons are dominant in poorly ventilated compartment irrespective of whether there is extinction or not (Alarifi et. al., 2014). The mechanisms which contribute to production of carbon monoxide are; i. Extinction of the flame. ii. Gases from partly burnt fuel. iii. Lack of air circulation in poorly ventilated compartments. iv. Reaction between the potentially combustible gasses and oxygen. For a self sustaining combustion to continue taking place the three main components supporting combustion must be present and they are oxygen, fuel and heat. Each of the above mentioned components is equally important for a fire to keep burning and that can be used as an advantage as suppression of any of the factors will lead to the fire being extinguished. Oxidizing agents are components which are not readily combustible but combine with fuel and support burning. This is mainly possible because oxidizing agents subjected to certain conditions undergo chemical reactions and yield oxygen which is a combustion catalyst. However most of the combustions readily combine with oxygen which is readily in the atmosphere for them to take place. In a scenario of fire extinguishing the firemen well understand the above mentioned principle and that allows them an upper hand in handling the fire. The most popular way used to set out a fire is pouring water on it using horse pipes from the fire engines (Chen, Lu, Li & Yuan, 2013). This is a way of suppressing one of the above mentioned conditions as the cold water instantly decreases the temperature of the combusting material (fuel) which in turn automatically puts out the fire. In cases where gas fire extinguishers are used nitrogen is mainly the gas component which is present in extinguishers .nitrogen has the effect of slowing down combustion and in high concentration it can completely stop combustion. Molecules of a matter are always in constant motion and in a fire the molecules are overcharged and thus move vigorously at a very high speed. The friction between these molecules is what brings about the heat. Heat can be generally described as a condition of matter in motion. On extinction most probably there is the emission of dark black soot which as earlier explained is due to incomplete combustion of combustible fuel. These fuels still have potential of reigniting and therefore it’s highly recommended that firemen ensure their complete extinction and also possibly get rid of any ignitable material (Chen, Lu, Li & Yuan, 2013). In addition to natural effects, reduction of the value/quantity of air also affects the burning intensity of a fire. Air deprivation on a burning fire leads to dilution of the main combustion catalyst oxygen which in turn brings down the fire burning intensity and the temperatures as well. Numerical Investigation into Compartment Fire Numerical approach to compartment fire is a simulation design where conditions present in a compartment fire are simulated and distribution of temperatures in the compartment and any open interconnections is studied and analyzed to give a generally precise view of what to expect in an actual compartment fire scenario (Johansson, 2014).According to Chen, Lu, Li & Yuan, M (2013),compartment fire dynamics are complicated and can only be described analytically with simplified theories due to the random behavior of fires and fire flames. Fire experiments are therefore a necessity in order to study and understand the compartment fire dynamics. There is a range of correlations available in the fire science literature, derived from empirical data got from actual experiments, which explains different factors contributing to a self sustaining fire. Fire experiments can be carried out in numerous ways including studying of some selected variables or carrying out the full experiment (Wen-Zhong & Shi-Jun, 2009). Experiments and attained outcome of experiments can be used to come up with data and generation of hypotheses. An ultimate observation is where investigation of an existing state is carried out without an attempt to alter or influence it. An example of this in fire science research is when real fire incidents are studied. Data collection by observation of a system and then deriving an extract of vital information from it is a common research aspect (Yao & Chow, 2006). The simulations are performed using a research code specifically developed for compartment fire prediction purposes. It is generally a based on structured finite procedures utilizing a general culvinear coordinated model with co-related velocity measure components smoothing the momentum and a pressure relation measuring algorithm. A fire thermal field can be precisely described by equating conservation of energy and combining it with its radiation modeled into an arithmetic combination. The combustion process is brought to a simulation by integrating a breakup system model. Thermal radiation in turn is modeled out by applying a ray tracing technique which determines the gas properties in a combustion process. A realistic fire environment can be easily modeled down to an appropriate size and manageable experiment by scaling down on all factors involved (Deckers, Haga, Merci & Sette, 2013). Experimenting with small-scale simulated experiments makes it possible to subject them to controlled factors as desired so as to study all possible probabilities in a real fire scenario. One can vary everything on the experiment as desired provided the factor of interest is kept constant and it can be analyzed to give some vital information on countering real fire occurring under the same circumstances and this can be quite helpful on enhancing fire fighting. This is because fire fighters have a general overview of what to expect and how to deal with the situation by putting compartment fire dynamics into action. However compromising some aspects is inevitable as one cannot possibly comply with the guidelines of scaling for all the factors involved in fire combustion. The above models enable full study and numerical analysis of compartment fire. All factors are able to be put into consideration with recording of numeric data which assist in making predictions on compartment fire behaviors. References Top of Form Alarifi A.A., Phylaktou H.N., Aljumaiah O.A., Andrews G.E., & Dave J. (2014). Effects of fire-fighting on a fully developed compartment fire: Temperatures & emissions. Fire Safety Journal. 68, 71-80. Top of Form Chen, B., Lu, S., Li, C., & Yuan, M. (2013). Analysis of Compartment Fires with a Ceiling Vent. Procedia Engineering. 62, 258-265. Top of Form Deckers X., Haga S., Merci B., & Sette B. (2013). Smoke control in case of fire in a large car park: Full-scale experiments. Fire Safety Journal. 57, 11-21. Bottom of Form Bottom of Form Top of Form Goo, J. (2012). Development of the size distribution of smoke particles in a compartment fire. Fire Safety Journal. 47, 46-53. Bottom of Form Top of Form Johansson, N. (2014). Numerical experiments & compartment fires. Fire Science Reviews. 3, 1-12. Top of Form Li, L., Cheng, X., Cui, Y., Dong, W., & Mei, Z. (2013). Estimation of smoke arrival time in tunnel fires. Tunnelling & Underground Space Technology. 38, 431-434. Bottom of Form Bottom of Form Bottom of Form Top of Form Lu, K., Hu, L., Delichatsios, M., Tang, F., Qiu, Z., & He, L. (2015). Merging behavior of façade flames ejected from two windows of an under-ventilated compartment fire. Proceedings of the Combustion Institute. 35, 2615-2622. Top of Form Yao, B., & Chow, W. (2006). Numerical modeling for compartment fire environment under a solid-cone water spray. Applied Mathematical Modelling. 30, 1571-1586. Top of Form Wen-Zhong Wu, & Shi-Jun You. (2009). Analysis to ventilation effectiveness in subway fire environment. 3215-3219. Bottom of Form Bottom of Form Top of Form Wu Wenzhong. (2010). Analysis of flame images of fire on site. 814-818. Bottom of Form Bottom of Form Read More

This means that smoke will move from the building compartment into the stairwell and this may have catastrophic effects on fire fighting. Stairwell extensions can also be subjected to a high pressure to deviate smoke from getting into them as these lobbies sometimes serve as refuge areas for fire survivors and fire fighters and they should be kept safe from smoke. It is highly recommended that high pressure be applied on the stairwells; this is to maintain a pressure balance between the fire invaded areas and the relatively low pressure stairwell.

This is attained by using separate pressurizing systems which generally balances the pressures. Fire burns more in well ventilated areas mainly due to oxygen flow which is the main factor in combustion. Ideally the burning compartment runs low on oxygen as the fire grows and so fire the fire burns out into the stairwell where there is plenty of oxygen to support its burning. The high pressure smoke can easily flow through building interconnections if there is no suppressing system put in place.

This can lead to a lot of smoke flowing into the corridors and stairwells if the entrances are not firmly closed. Expansion of heated air brings about a lot of pressure which can force open doors if not firmly closed (Wu, 2010). Openings on the stairwell come in handy in helping relieve the stairwell of smoke. This is done by allowing smoke flow out of the burning compartment into the low pressure stairwell area where due to pressure difference between the stairwell and the outside the smoke is able to flow out.

Generally openings in a fire scenario tend to balance pressure between the outside and the inside which helps keep the conditions of a burning compartment more or less same as the conditions outside. They also help in managing of combustion in a burning compartment to prevent back draft. Alarifi et. al. (2014) asserts that a back draft is an occurrence where oxygen is re-introduced into an otherwise gas-phase combustion which leads to a rapid ignition which sometimes comes in form of an explosion.

These posses a great threat to fire fighters and must be prevented at all costs. A hole on the highest point of a room provides adequate ventilation which allows heat and the hot gases (smoke) to escape .this brings about a somehow cooling effect to the burning compartment and prevents further combustion of hot gases and the possibility of a backdraft occurrence. Effect of Fire Fighting on a Fully Developed Compartment Fire Flame/fire extinction is where a fire or combustion is brought to a stop prematurely by suppressing one or even more of the necessary conditions which are necessary for combustion to take place.

Extinguishing a flame has great relation with incomplete material combustion as in both cases there is presence of potentially combustible material which would otherwise have burned to completion under normal circumstances (Alarifi et. al., 2014). This is the case in fire fighting where the normal conditions for combustion are interrupted in the act of putting out fire either by pouring water or using nitrogen. This leads to production of partly burnt hydrocarbon gases, hydrogenous gases and carbon monoxide.

If the percentage of the oxygen gas in a compartmental fire incident falls below a certain point it leads to presence of partly combusted substances. This can be attributed to the flame being put off when it is at different stages of combustion depending on the flammability of the materials. The mechanism involved in putting off a flame is believed one of the main factors leading to massive emition of carbon monoxide from fires. In poorly ventilated compartments, fire extinction brings about emitions of readily combustible fuel mass in form of gases leaking out through the ceiling.

These readily combustible gases can also react with the low percentage of oxygen present in the compartment depending on the current temperatures of the compartment.

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