Enclosure Movement Compartment Fire Propagation - Term Paper Example

ENCLOSURE FIRE DYNAMICS Student’s Name Institutional Affiliation Tutor’s name Course Date Fire Dynamics Question One In combustion of any carbon substances, carbon monoxide is produced due to incomplete burning. Carbon monoxide burns in the presence of adequate oxygen to form carbon dioxide. At a high heat flux of 5 KW, the heat is so immense such that complete combustion of carbon fuel takes place in the compartment producing carbon dioxide instead of carbon monoxide. In addition, in a compartmental fire such as this one, the fire and heat is constraint within a space ensuring only gases from complete combustion leaves the compartment to the surrounding spaces. Consequently, only a trace of incomplete combustion can be detected few metres away from the compartment. Question Two Poly (Methyl methacrylate) (PMMA) is a thermoplastic material. PMMA thermally decomposes to undergo both physical and chemical changes. When exposed to sufficient heat flux, PMMA fire melts and the viscosity of may vary depending on the molecular weight of PMMA used. Higher molecular weight PMMA leads to high viscosity while the lower molecular weight PMMA tends to flow easily (Ohlemiller&Shields, 2008). According to Ohlemiller and Shields (2008), PMMA thermally degrades to its monomers, which is highly volatile at the conditions in the firebox experiments. Therefore, the occurrence of end-chain scission is needed to remove individual monomer at the end of the chain (Beyler &Hirschler, 2012). Question Three Hydrocarbons burn in the presence of oxygen to form water and carbon dioxide. The products of normal combustion of hydrocarbon fuel would include the fuel and the two mentioned above. Ethene is unsaturated hydrocarbon, therefore, ethene is reactive, and it burns in the presence of oxygen producing water, carbon dioxide and unburned ethane (Nave, 2014). In ideal combustion, it is assumed all ethene molecules are consumed in the fire producing carbon dioxide and water. Ethene is made up of covalent bonds where adjacent atoms share valence electron. Therefore, the double bond in ethane is made up of both sigma and pi bonds, each degrade at different degree. Sigma bonds are formed when similar orbitals overlap while Pi bonds are formed when similar adjacent p orbitals overlap (Vollhardt & Shore, 2007). Chemically, the pi bonds are weaker than the sigma bonds. Pi bonds have a high electron density compared to sigma bonds. The upper carbon-carbon usually breaks first in a chemical a reaction due to the high number of pi bonds compared to the lower carbon-carbon bond. Subsequently, when ethene is exposed to heat flux, the upper double bond breaks first. Due to the difference in the electron density in the double bonds between the carbons, the lower bond is more rigid than the upper one. Heat will easily break the less rigid bond first making the upper carbon-carbon susceptible to heat degradation. Question Four Perfect combustion of DMN (C2H6N2O) in air i. Balanced equation ii. Maximum possible yields of carbon dioxide and water. In perfect combustion, all DMN would burn producing the three products namely water, carbon dioxide and nitrous oxide. 2 moles of C2H6N2O (74g*2) will burn to produce 4 moles carbon dioxide and 6 moles of water. Therefore, 4 moles of carbon dioxide which is a 100% yield Similarly, 6moles of water, which is also a hundred percent. If DMN was not perfectly combusted in air, then the maximum possible yield of COandCO2 will remain same as the perfect combustion because no limiting weight has been provide. Question Five COOH From on the onset of the diamgram, it has a carboxylic end. Therefore, the substance belongs to a carboxylic group. The substance can also be written as CH3 (CH=CH)2COOH. Subsequently, the substance given is known as sorbic acid. The substance is also known as (IUPAC name) is (2E,4E)-hexa-2,4-dienoic acid (Farmer & Reusch, 2013). The bonds that would be broken when ideally combusted in pure oxygen include: carbon-carbon single bonds, carbon-carbon double bonds, carbon-oxygen double bond, carbon-oxygen single bond, hydrogen-oxygen single bond and carbon-hydrogen single bond. However, some types of the bonds mentioned above will still be part of the products. For instance, carbon-carbon single bond will be in carbon dioxide, and hydrogen-oxygen single bond will be in water. In addition, some of the bonds mentioned exists more than once in the sorbic acid’s structure. Question Six Fire causes burns on human bodies and the degree of burns differs. Some categories a superficial, partial-thickness and full thickness burns. In superficial burns, which are sometime referred to as the first-degree burn, the outer skin (epidermal) is damaged, red in colour, painful and slightly swollen (National Health Services, 2013). At times, dermal may be slightly damaged forming a few blisters, but still falls under superficial burns (NHS, 2013). Partial-thickness burns or deep dermal burns, which is also known as second-degree burns affects the first two layers of skin; epidermis and dermis. Both the epidermis and dermis are damaged. It is characterized by red and blotchy skin, blister formation, swollen and very painful experience (NHS,2013). In full thickness burn, all the three layers of the skin (epidermis, dermis,and subcutis) are damaged. In most cases the skin is burnt away and the tissues beneath the skin remain black. The remaining part of then skin will be white, brown or black, and dry (NHS, 2013). The skin tends to have a leathery or a waxy texture (The University of New Mexico, 2013). Eschar is a dead tissue coming off the skin. Eschar, in most cases, as a result of burns. It forms part of a healing process,coming off to allow a newly developed skin to flourish. Eschar appears in the Lund-Browder chart as part of the types of burns mentioned above. Question Seven Reseachers have carried out many fire experiments to understand compartmental fire propagation and growth. Zone and field models are used in understanding the behaviour of fires, from how they start and how to manage them. The two models operate based on principle of conservation of energy, mass, and momentum (Weicheng & Maohua, n.d). The models are used to predict fire behaviours on assumption that physical parameters to be uniform within a control volume (compartment). In zone models, a basic element of fire is divided into various zones over which conditions are uniform (Weicheng & Maohua, n.d). The two main zones assumed are a hot upper smoke layer and a lower cooler layer. The two zones are assumed to be at the same temperature, smoke, and gas concentration ((Weicheng & Maohua, n.d). The main advantage of the model is the simplification of ordinary differentials equations. The main disadvantage is that the model only gives an overall view without finer details that might result in errors in certain scenarios. In field model, fire element is based computational fluid dynamics technology. The compartment is divided into field variables such as gas concentration and temperature (Weicheng & Maohua, n.d). Large number of partial differential equations must be computed numerically. Therefore, this model yields much more details than zone model. The disadvantage is that it requires computation that is more intensive due to the large number differential equations involved (Gorbett, 2011). Question Eight Heat radiation Where Where and The heat is being radiated from surface A1 to surface A2 2.15m below. m Therefore, The respective terms in the F12 equation are computed separately as given in the proceeding calculations; Hence, Inserting all values in the original formula, the rate of heat transfer from the smoky layer to the floor is given as below. is the heat absorbed by the floor. Question Nine Density 2300 kg m-3 Thermal conductivity 0.85 W m-1 K-1 Specific heat capacity 847 J kg-1 K-1 Thickness of board 8mm Initial/ambient laboratory temperature 18°C Ignition temperature 415°C Useful formulae: Where Thermally thin case It is assumed that the material will behave thin even for higher heat fluxes (Delichatsios, 2000). Time of ignition for this case is given as follows, Thermally thick case Time of ignition for this case is given as follows. Inserting the respective values in the formula gives Taking the mean temperature of the two scenarios by getting the average gives, Therefore, 10kW/m2 will not ignite in ten minutes the new type of insulating board that has been developed. References Beyler, C.L. & Hirschler, M.M., 2012. Thermal decomposition of polymers. Availabe at: [Accessed 09 Nov 2015] Delichatsios, M.A., 2000. Ignition times for thermally thick and intermediate conditions in flat and cylindrical geometries. Fire Safety Science, 6: 233-244. doi:10.3801/IAFSS.FSS.6-233 Farmer, S. & Reusch, W., 2014. Nomenclature of carboxylic acids. Available at: [Accessed 10 Nov 2015] Gorbett, G.E., 2011. Computer fire models for fire investigation and reconstruction. Available at: [Accessed 09 Nov 2015] National Health Services, 2013. Burns and scalds-symptoms. Avaialbe at: [Accessed 09 Nov 2015] Nave, R., 2014. Alkenes. Available at: [Accessed 10 Nov 2015] Ohlemiller, T.J. & Shields, J.R., 2008. Aspects of fire behavior of thermoplastic materials. Availbe at: < http://fire.nist.gov/bfrlpubs/fire08/PDF/f08001.pdf.> [Accessed 08 Nov 2015] The University of New Mexico, 2013. Burns classification. Available at: [Accessed 10 Nov 2015] Vollhardt, K. P.C. & Shore, N. (2007). Organic Chemistry (5th Ed.).  New York: W. H. Freeman. Weicheng, F. & Maohua,Z., n.d. Review of modelling of fire physics and risk assessment. Available at; [Accessed 10 Nov 2015] Read More