The Fire Dynamic Enclosure - Assignment Example

Student Name: xxxxxxxxxx Tutor: xxxxxxxxx Title: Firе Dynamic Еnсlоsurе Date: xxxxxxxxxx ©2016 1. Explain why there are only trace levels of CO a few meters from the outside of a compartment when there is a 5MW fire burning (“bouncing”) inside.[175 words] The abrupt introduction of air into the combustion chamber results in the rapid combustion of the hot products as portrayed by the presence of intense flames. It is because of the rapid or sudden introduction of air into the chamber which is deficient in oxygen. The chamber has in before the introduction of air, hot and incompletely burned products. There are at times where this introduction of air results in an explosion according to (ISO 13943, 2008, 4.21). Deflagration which is an occurrence experienced when the air is abruptly pumped or released into a confined space containing incompletely burned or combusted products which are hot. Carbon monoxide which is a flammable is produced as a result of the heating. Deflagration mainly occurs in a confined area, for instance, the tightly closed aircraft fuselage in case burning takes place undetected and thus causing all oxygen to be consumed. When it still hot, the introduction of air into the chamber or any opening causes it to burn explosively. Thus, it is only trace levels of CO a few meters from the outside of a compartment when there is a 5MW fire burning (“bouncing”) inside. 2. Why is it an advantage, for the burning of PMMA in firebox experiments, that end- chain scission occurs in the polymer? PMMA (Polymethyl methacrylate) has very unique characteristics in comparison with other plastics, such as, its high light transmission, has an extremely long service life with specific properties such as high resistance to UV light. Also, it has no limitation to weathering and has unlimited coloring options. In addition, the PMMA exhibits the hardest surfaces compared to all other thermoplastics. PMMA can be made into the various forms which are required for any thermoplastics and it is 100% recycled and thus gives it a very vital property that is saving the environment and also the natural resources. Being as clear as glass, PMMA can be a proper replacement for glass. The density PMMA is 1.17–1.20 g/cm 3, which is less than half that of glass. It also has good impact strength, higher than both glass and polystyrene; however, PMMA's impact strength is still significantly lower than polycarbonate and some engineered polymers. PMMA ignites at 460 °C (860 °F) and burns, forming carbon dioxide, water, carbon monoxide and low-molecular-weight compounds, including formaldehyde. 3. When ethene is ideally combusted in pure oxygen: One of the carbon-carbon bonds breaks first. Which one and why? [250 words] A reaction under which only ethane and oxygen are present is an example of an ideal situation since, in a typical reaction where air reacts with ethane, there are other constituencies. The product of this reaction is co2, water and energy and the reactions are commonly referred to as combustion or burning. During the reaction, heat is produced, this is an exothermic reaction. It is because the amount of heat required for the breaking of bonds is higher than the quantity of heat released. This is to say that the energy accumulated in the reaction is less than the energy that is absorbed for the reaction to take place. To burn a hydrocarbon, heat is needed to produce a spark. The heat is imperative to be able to break the carbon-carbon bond, the carbon-hydrogen bond as well as the oxygen-oxygen bond. To break the typical Carbon-Carbon bond, 350 kJ/mol in required; 413 kJ/mol for C-H bond, whereas the O-O bond requires about 498 kJ/mol. The carbon-carbon bond consists of two types of bonds; that is the sigma bond and the pi bond. In general, during the reaction of the alkenes, the carbon-carbon bonds are broken. The breaking of the bonds that is the Sigma and the pi bonds. The pi bond is the first one to break because it is the weaker bond. This leads to the formation of two sigma bonds which are stronger in a reaction called addition reaction. 4. Name the following substance and list all of the bond types that would be broken if it is ideally combusted in pure oxygen. COOH The substance is carboxylic acid Bonds to be broken are: hydrogen oxygen bond, carbon-carbon bonds, oxygen-oxygen bond and the C-OH bond. 5. Critically review and distinguish superficial, partial-thickness and full thickness burns and explain the significance of ‘eschar’. How would/could eschar appear on a Lund-Browder chart? [300 words] Burning is classified in terms –of whether it is a superficial burn or a partial thickness burn or a full thickness burn. This is about the depth in which the burn has penetrated. The superficial burn is as its name suggests, this burn affects only the outer layer, which is the epidermis. This burn causes the skin to be red and is usually very painful. This burn can be compared to the superficial sunburn but without the blisters. This kind of a burn heals after 3-5 days and the need for a hospital is mainly for regulating pain and fluid balance if need be. Partial thickness burns are usually burns in the second degree. In this burns, blisters are formed, and the whole epidermis and the upper art of the dermis are affected. The burn causes a pink, red wound which is wet and painful to be formed. This wound takes 10-21 days to heal that is if grafting is not involved. The scar formed is usually small, however if pressure is applied to the wound, it blanches. The full thickness burn is lethal. All the epidermis and most of the dermis are destroyed. The wound appears red or white, and it can be dry. This wound mainly may require grafting or excision so that it can heal. An eschar refers to dead tissue which is formed on the surface of the skin especially in wounds caused by burns. It should be very carefully handled, especially to patients whose immunity is weak since it can lead to infections and even skin cancer. 6. Critically review zone and field models used for compartment fire modelling. Provide examples and critically analyse the main assumptions, limitations, advantages and disadvantages of these models. The use of Modeling and Zoning of Fire enables the user to appreciate the pros and cons of a given fire modelling and the appropriate model to be used in a given situation. There are different types of models which are used in the zoning of fire. These models are: Algebraic model This is the very first step of fire modelling that involves the formulation of equations. The equations estimate the way the fire behaves, for instance, the flame height, heat release rate, plume, the ceiling jet velocities, gas layer temperatures and depth, radiation. The equations provide results the state of the fire and thus give information for a particular moment in time. Advantage The advantage of using the algebraic model is that they can provide an immediate answer to simple fire dynamics questions. The general fire situation and the results obtained are based on the data obtained from the test Disadvantage The disadvantage of using algebraic models is that It is more effective for a simplified fire situation. The information provided is also can be done only for a single property. Zone Models In v the case where the algebraic models do not offer significant details for the fire, sufficient to give the fire situation at hand. The zone model is appropriate for this case. In this model, space is partition into small volumes called zones, and then algebraic equations are applied. In this model, factors such as Temperatures, velocities and other properties are assumed to be uniform within these zones. Advantages As a result of advancement in technology, there are more capabilities to simulate even more complex fire phenomenon which are experienced in the field in a matter of a few minutes. Disadvantages However, in some zones models may not be consistent in terms of the results with the other models and therefore they have to take as an assumption. References Kao, C.C. and Garner, W.L., 2000. Acute burns. Plastic and reconstructive surgery, 105(7), pp.2482-2493. Read More