The Different Extinguishing Methods of Fires - Assignment Example

University of Central Lancashire School of Engineering FV1001 Assignment Brief Assignment Details Please answer ALL questions, showing workings, calculations and drawings where appropriate. Section A – Answer all questions in this section, include appropriate referencing and word count. 1. In approximately 250 words discuss the different extinguishing methods of a water, a powder and a carbon dioxide fire extinguisher. Water: This type of fire extinguisher is used in cooling of burning materials. In order to achieve the result of extinguishing fire, it uses the air-pressurized water and water mist technology. In the air-pressurized water technology, the heat in the burning materials is cooled by absorption. This type of fire extinguishing using water is best used in class A fires only. For the case of water mist, it uses the misting nozzle in order to break up the stream of water which is deionized to a point where there is no conduction of electricity towards to the operator. In addition to the above, water is also mixed with other wet chemicals as an additive and it is used in fire extinguishing. Such chemicals include wet chemicals, antifreeze chemicals and wetting agents (Army Test and Evaluation Command Aberdeen Proving Ground MD. 1971). Powder: A powder fire extinguisher is in most cases used when fire occurs in a car, garage, a house. a caravan and even in a boat. The powder fire extinguishers are available for both domestic and any other industrial fire cases. In many instances, these fire extinguishers can be used to extinguish different types of fire. These types of fire can be classified into various classes ranging from class A to class E. In detail,the classes include; Class A ( textiles. Wood, plastics paper and rubber), class B (liquids that are flammable), class C (gases that are combustible) and lastly class D (equipment that is electrically energised). The powder deprives fire the source of fuel by absorbing most if not all the molecules of fuel (Army Test and Evaluation Command Aberdeen Proving Ground MD. 1971). It mainly separates the fire tetrahedron thus preventing the major chemical reactions among the heat, oxygen and fuel components. As a result, the powder then becomes an effective fire extinguisher. Carbon dioxide: Carbon dioxide is a gas well known for its non-conductivity and non-corrosive properties. This gas forms one of the major components in the atmosphere hence it is easily extracted and stored in liquid state at high pressure. This type of fire extinguishers is commonly used in class B (liquids that are flammable) and class E (equipment that is electrically energised). This type extinguishes fire by depriving the oxygen required by the fire. When the oxygen reaches insufficient levels, the fire is effectively put off (Army Test and Evaluation Command Aberdeen Proving Ground MD. 1971). 2. In approximately 250 words explain what is meant by, and the differences between, prescriptive and performance based design. Prescriptive design is an approach used in design that takes into consideration the past experiences in design by using specific building codes that are available for each design exercise to be undertaken. This approach is majorly related to a number of components which may include; the construction method, the workmanship, material properties including the type and quality of the materials in use. It has clearly stated design laws as well as codes and other standards of design that must be adhered to (Lataille 2003). This method of design therefore is very effective, fast and most importantly less costly. Performance based design on the other hand is an approach used in design that is geared towards achieving some intended measurable performance requirements. In this approach the method to be used in attaining the intended requirement is not provided. In other words, the performance based design is only interested in the end product rather than the means of achieving the qualities of the end product (Lataille 2003). This therefore makes this approach a more expensive one as compared to the simpler and straightforward prescriptive design approach. Performance based design mainly focuses on the intended performance of the building while in use. It is mainly based on two major principles; the requirement of the users and the performance supply, the requirement for the result validation and verification against a given set of targets for performance. Therefore, in applying this design approach it is important to identify and formulate different requirements of the intended users, then be able to transform the requirements of the users into requirements of performance and lastly assessing the probability and effectiveness of the proposed solutions by applying design and tools used in evaluation to meet the required levels (Lataille 2003). 3. In approximately 250 words explain the difference between complete and in-complete combustion. Combustion is a reaction that results to heat, this involves a fuel such as petrol and an oxidant. The amount of oxygen/oxidant available results to two main types of combustion i.e. the complete and incomplete combustion (Lataille 2003). Complete combustion refers to the type of combustion that takes place when a ample supply of oxygen is constant the optimum temperature is experienced while incomplete combustion takes place when the amount of oxygen supply is limited hence insufficient. In complete combustion, the products are few i.e. carbon dioxide and water while the products of incomplete combustion can be many and in varied proportions i.e carbon monoxide and many other carbon particles (Lataille 2003). Complete combustion results to more energy production from the fuel being reacted than the incomplete combustion. In most instances, incomplete combustion results to a lot environmental pollution as a result if the carbon monoxide produced and the various carbon particles as compared to complete combustion in which only carbon dioxide and water are produced (Lataille 2003). The carbon monoxide contributes to the destruction of the ozone layer and can even lead to death when in contact with blood cells. Carbon dioxide on the other hand is stable since it is in its oxidized state and can also be taken up by other living organisms such as plants for photosynthesis. This therefore means that carbon dioxide, a product of complete combustion is not a major environmental pollutant. Complete combustion is always characterised by a blue flame while the flame of incomplete combustion is always orange. The orange colour is as a result of the unburned carbon particles present in the flame. 4. In approximately 250 words explain the difference between premixed and diffusion flames. Premixed flame is produced when the fuel used and the oxidiser are mixed totally before reaching the flame while the diffusion flame is produced when the fuel to be used and the oxidiser are separately provided and ultimately mixes with each other mainly in the zone for mixing (Lataille 2003). The diffusion flame in most cases tends to be stable while the premixed flame forms a propagating wave front. In diffusion flames, the diffusion rate is very important since it determines the rate at which the fuel and the oxidiser will combine which does not apply to premixed flames (Lataille 2003). Diffusion flames also burn slower than the premixed flames The diffusion flames produce more soot than the premixed flame in some instances due to insufficient supply of the oxidant for the reaction resulting to an orange colour of the flame. Premixed flames results to a more localized front of the flame than the diffusion flame. Premixed flames are mostly dangerous since they are produced at very high temperatures as compared to diffusion flames which are produced at very low temperatures. Premixed flame does not pollute the environment since they do not produce a lot of soot while the diffusion flame produces a lot of soot hence polluting the environment. In terms of flame thickness, the premixed flame is much thinner than the diffusion flame. Due to the higher temperatures required in the production of the premixed flames, nitrogen oxides are produced in larger quantities, this may impart the environment negatively i.e. as a result of the acid rain, on the other hand, diffusion flames do not require very high temperature hence the nitrate oxide compounds are not produced (Lataille 2003). 5. In approximately 250 words discuss the objectives of fire safety and the five tactics available to the fire safety designers seeking to fulfill the fire safety objectives? The main fire safety objectives include: To reduce the occurrence of fires and fire impact To specifically target those people that are at the highest risk of fire impact. To come up with regulations that protects occupants of any building from fire. To ensure that the planners and designers of any building consider the safety of all the building occupants. To ensure that potential risks of fire outbreak are identified and dealt with in time. To ensure that the response time after a fire outbreak is as fast as possible by using the available resources in a flexible manner. To minimise the cost incurred in case of a fire outbreak. To improve the services offered to all people to ensure safety at all times. To ensure that the management and leadership results in a healthy and safe population. To make sure that the fire brigade staff and all people in any region have the necessary skills involving the fire safety for all and the knowledge required in case of fire. To ensure proper collaboration between the fire brigade personnel the all people in any society to ensure that safety is achieved in the region by involving all people in the region. To increase the most needed workforce to ensure that all people can be served to ensure their safety To always apply the most sustainable mechanisms in ensuring the fire safety of any given population. Some key tactics can be applied by the fire safety designers. These tactics include: The designers may provide sprinklers in areas where the fire outbreak risk is highest. The designers may also consider the use of construction material that reduces the fire spread. The designers should also consider fire fighting as the key component in any building construction. To provide for fire escape routes, which are well marked to ensure safe escape of the building occupants in the event of fire. In the design, it also important to provide safe areas where the building occupants can assemble in case of fire to allow for safe extinguishing and evacuation from the premises. Section B - Answer all 8 questions below, show your workings and include appropriate referencing 1. Convert the following temperatures into Kelvin: a) 12°C b) -177°C c) 1233°C d) 392°C 2. How many moles of carbon are in 245.0g? 3. Balance the following equations: a) Ca(AlO2)2 + HCl → AlCl3 + CaCl2 + H2O Ca(AlO2)2 + 8HCl → 2AlCl3 + CaCl2 + 4H2O b) Fe + O2 + H2O →Fe(OH)2 2Fe + O2 + 2H2O →2 Fe(OH)2 c) MgNH4PO4 → Mg2P2O7 + NH3 + H2O 2MgNH4PO4 → Mg2P2O7 + 2NH3 + H2O d) AlCl3 + Ca3N2 → AlN + CaCl2 2AlCl3 + Ca3N2 = 2AlN + 3CaCl2 e) C15H26 + O2→ CO2 + H2O 2C15H26 + 43O2 = 30CO2 + 26H2O 4. Ammonia and oxygen react to form nitrogen and water: a) How many grams of O2 are needed to react with 6.0 moles of NH3? b) How many grams of N2 can be produced when 5.45g of O2 react? Therefore, But, c) How many grams of water can be formed from the reaction of 43g of NH3? 5. How many joules of heat are needed to raise the temperature of 43.0g of aluminium from 22°C to 55°C, if the specific heat of aluminium is 0.90J/g°C? 6. Using the Ideal Gas Law solve the following problems: (use 0.08206 L atm mol¯1 K¯1 or 8.314kPaL/molK for the gas constant). a) If 4.7 moles of propane are at 28ºC and under 154.2kPa of pressure, what volume does the sample occupy? Therefore, b) Determine the volume occupied by 3.34g of carbon dioxide gas at STP. Thus, c) A sample of argon gas at STP occupies 46.2L. Determine the number of moles of argon and the mass in the sample. Thus, And Therefore, the mass in the sample is given as; d) At what temperature will 0.654 moles of neon gas occupy 12.30L at 1.95 atmospheres? Therefore, e) A 30.6g sample of gas occupies 22.414L at STP. What is the molecular weight of this gas? At STP, Therefore, Also, from; 7. A sample of carbon monoxide at 57ºC and under 0.67atm of pressure takes up 85.3L of space. What mass of carbon monoxide is present? (5 Marks) From, 8. A pan 200mm diameter pan is placed on a stove to boil some water (see figure 1 page 4). The thickness of the bottom of the pan is 7.5mm and the inner surface temperature of the bottom of the pan is 150°C. Determine the outer surface temperature of the pan if the pan was a. Aluminium b. Copper Solution The general calculation include; Also, since the fluid involved is water whose boiling point is , then Also, from the thermo physical properties of matter tables, the saturated water, liquid at 100 0C Parameter Value 1.76 0.0589 N/m On the vapour side, 0.5956 kg/m3 Thus, the rate of heat transfer rate per unit area is found by the following formula a) Aluminium, Assume one-dimensional, steady state conduction through the bottom of the pan; Thus, the heat transferred from aluminium is obtained as; Thus, from the supply energy from the stove, the equation becomes Thus b) Copper. Assume one-dimensional, steady state conduction through the bottom of the pan; Thus, the heat transferred from copper is obtained as; Thus, from the supply energy from the stove, the equation becomes Thus Figure 1: Pan set up Works cited Army Test and Evaluation Command Aberdeen Proving Ground MD. 1971. Fire Extinguishers. Ft. Belvoir, Defense Technical Information Center. Lataille, J. I. 2003. Fire protection engineering in building design. Amsterdam, Butterworth-Heinemann. Read More