An Understanding of Compartment Fires - Lab Report Example

Introduction This experiment gives opportunity to the students to have understanding of compartment fires with the information involved being both descriptive and scientific. The aim of performing the experiment is the assessment of the development of compartment fires from ignition point, through flashover to decay. A compartment fire is a fire in enclosed space. Fuel controlled compartment fire is where there is adequate air to enable reaction with all the fuel in the enclosure while ventilation limited is where there is insufficient air available. Fire box This is small scale compartment that has a roof, floor and walls having a thickness of 0.025m made of monolux lining with one wall being constructed of fire resistant glass. The fire box doors are adjustable so that it is possible to study effect of ventilation size on the fire. In the floor of the fire box there is one hole in which an axle passes in order to support the fuel which rests on the balance below, so as to make the recording of weighed material possible. The fire box is fixed inside a steel frame that has wheels so as to make it easy to effect movement whenever it is required. The firebox has three columns of four thermocouples in the rear wall of the compartment with one thermocouple protruding through the floor hole with their distribution being as can be seen in figure 1. The measurement of temperature is effected through use of thirteen thermocouples in the experiment which are type k (nickel-chrome/nickel-aluminium) having stainless steel sheet. Twelve of the thirteen thermocouples are used in the measurement of the inside temperature on the rear wall of the compartment while the remaining one thermocouple protrudes through the floor hole. The thermocouple arrangement is as can be seen in figure 1 and there is connection of the thermocouples to a squirrel data logger where the temperature in the compartment is recorded. Experiment materials Fuel (PMMA) Square slabs of PMMA (Polymethyl Methacrylate) are burned in small-scale fire compartment. This material is commonly used in small-scale compartment fire experiments where one sample is burned for each test. Experiment procedure The firebox dimensions were measured and recorded including the thickness on monolux, the position of thermocouples as well as the location of the fuel support. The thermocouples were cleaned as a precaution of ensuring readings were not to be affected by soot or any form of dirt and then there was connection of the cleaned thermocouples to the Squirrel data logger with recording of which channel applied to which thermocouple. The dimension of the sample fuel were measured and recorded. It was ensured that the balance was switched on, the fuel tray was placed on the axle inside the firebox, then the Tare button was pressed and it was ensured that the reading registered on the balance was ZERO. A fuel was placed on the tray, with a 5g PMMA being added so as to enable the ignition of fuel sample and fast spreading of the fire through whole surface of the PMMA. There was recording of the mass of the PMMA fuel and a suitable table was created for recording the weight of the sample, the smoke layer height and observation of every minute of the duration of the test which lasted for about 30 minutes. It was ensured that the smoke extract system was switched on and the vent opening was at the desired size and then the squirrel data logger was started. The fuel was then ignited, the door opening adjusted to required size, a sample paper placed inside the firebox just to the inside of the vent opening and the observation were recorded. There was recording of the weight of filter paper and after 5 minutes elapsing, the filter paper was held inside the opening at the top for 2 minutes using tongs. The weight of the filter paper was recorded and a repeat of the same at regular intervals. After 10 minutes ,the opening was closed, and kept closed for 20 seconds before being re-opened. This was repeated after 5 minutes with observations being recorded and the squirrel data logger was then stopped when he fire died down. Requirements Experiment 1+2 – Full size opening: Compartment –(from cold,from hot) Experiment 3 – Half –size opening: compartment –(from hot) Results Exp. Door height Door width Fuel Area Original Mass Total Duration Flashover Back draught Soot deposit 1 21 16 15x15 47g 21:44:12 Yes No 1.68 2 21 16 15x15 g 13:51:58 Yes No 1.68 3 21 16 15x15 g 32:04:85 Yes No 1.68 Results First test The first test involved full ventilation with cold compartment. The fuel was all over the surface in the first minute and in the second minute the fuel was concentrated at the middle. After about three minutes fire was seen starting on the hard part. After about six minutes the fire was developed on the fuel and a sizzling like sound was heard. After eight minutes fire started rising with tenth minute realizing an increase in the size of fire. At the seventh minute a temperature of 320 degree was recorded. After about 19 minutes flashover occurred and this was detected by a paper which was placed around the door smoking which is an indication of flashover. In this test there was no backdraft. Table 1 gives the summary of mass loss with time and figure 1 gives a pictorial representation of the same. It can be seen that there was a constant mass loss as the fuel continued burning. Table 1 Time (minutes) Per minute Mass loss(mg) Mass loss(mg) Mass loss 1 2165.2 2165.2 2.1652 2 2185.2 4350.4 4.3504 3 2195.3 6545.7 6.5457 4 2197.9 8743.6 8.7436 5 2193.1 10936.7 10.9367 6 2184.5 13121.2 13.1212 7 2178.6 15299.8 15.2998 8 2149.5 17449.3 17.4493 9 2099.7 19549 19.549 10 2049.4 21598.4 21.5984 11 2031 23629.4 23.6294 12 2073.3 25702.7 25.7027 13 2118.7 27821.4 27.8214 14 2068.2 29889.6 29.8896 15 2021.8 31911.4 31.9114 16 2109.5 34020.9 34.0209 17 2150.4 36171.3 36.1713 18 2183.5 38354.8 38.3548 19 2154.2 40509 40.509 20 2137.7 42646.7 42.6467 21 2128.9 44775.6 44.7756 Figure 1. Second test Table 2 gives a summary of the mass loss as the test progress where it can be seen that the second column gives the mass loss in each of the indicated minute. In the first minute 2006.1mg (2.0061g) was lost while in the second minute 2145.2mg (g) was lost. It can also be seen that it was in the twenty third minutes when there was the highest loss of mass of 2099.3. in column three the cumulative mass loss (mass loss) has been given where it is seen that mass loss in 2 minutes was 4151.3mg (4.1513g). After 6 minutes it can be observed that 12.7126g of mass had been lost. Figure 2 it can be seen that there is almost a linear relationship between time and mass loss. Time (minutes) Per minute Mass loss(mg) Mass loss(mg) Mass loss 1 2006.1 2006.1 2.0061 2 2145.2 4151.3 4.1513 3 2135 6286.3 6.2863 4 2146.3 8432.6 8.4326 5 2133 10565.6 10.5656 6 2147 12712.6 12.7126 7 2138.4 14851 14.851 8 2161.1 17012.1 17.0121 9 2135.3 19147.4 19.1474 10 2152.5 21299.9 21.2999 11 2142.1 23442 23.442 12 2161.1 25603.1 25.6031 13 2142.9 27746 27.746 14 2133 29879 29.879 15 2129 32008 32.008 16 2118 34126 34.126 17 2113.2 36239.2 36.2392 18 2112.1 38351.3 38.3513 19 2107 40458.3 40.4583 20 2095.2 42553.5 42.5535 21 2079 44632.5 44.6325 22 2098.1 46730.6 46.7306 23 2099.3 48829.9 48.8299 24 2089.1 50919 50.919 25 2079 52998 52.998 26 2075.5 55073.5 55.0735 27 2067.3 57140.8 57.1408 Third test Table 3 gives a summary of the mass loss as the test progress where it can be seen that the second column gives the mass loss in each of the indicated minute. In the first minute 1688mg (1.688g) was lost while in the second minute 1.686.5mg (g) was lost. In the table it can also be observed that it was in the second minute when there was the highest loss of mass of 1686.5. In column three the cumulative mass loss (mass loss) has been given where it is seen that mass loss in 2 minutes was 3374.5mg (3.3745g). After 6 minutes it can be observed that 10.0966g of mass had been lost. Figure 3 it can be seen that there is almost a linear relationship between time and mass loss. Table 2 Time (minutes) Per minute Mass loss(mg) Mass loss(mg) Mass loss 1 1688 1688 1.688 2 1686.5 3374.5 3.3745 3 1683.9 5058.4 5.0584 4 1682.1 6740.5 6.7405 5 1679.8 8420.3 8.4203 6 1676.3 10096.6 10.0966 7 1671.9 11768.5 11.7685 8 1666.2 13434.7 13.4347 9 1659 15093.7 15.0937 10 1651.8 16745.5 16.7455 11 1643.3 18388.8 18.3888 12 1635.4 20024.2 20.0242 13 1627.1 21651.3 21.6513 14 1618.2 23269.5 23.2695 15 1610.1 24879.6 24.8796 16 1601.8 26481.4 26.4814 17 1593.6 28075 28.075 18 1584.2 29659.2 29.6592 19 1575.2 31234.4 31.2344 20 1565.1 32799.5 32.7995 21 1554.4 34353.9 34.3539 22 1545.7 35899.6 35.8996 23 1538.1 37437.7 37.4377 24 1532.2 38969.9 38.9699 25 1526.1 40496 40.496 26 1521.9 42017.9 42.0179 27 1519.5 43537.4 43.5374 28 1518.1 45055.5 45.0555 29 1517.2 46572.7 46.5727 30 1516.5 48089.2 48.0892 31 1516.1 49605.3 49.6053 32 1515.8 51121.1 51.1211 33 1515.6 52636.7 52.6367 Discussion From the graphs it could be seen that there was a general trend of the mass reducing with. The general trend where there was a reduction in mass could be attributed to the fuel being turned into gaseous products which escaped through the door. The behavior of the fire in this experiment is useful in prediction the behavior of fire in real life situation. The fire fighter need to know the point where flash over may occurring when an incident of fire occurs. This will help in ensuring that all safety measures are taken at that point. References Fleischmann, C. M., and Parkes, A. R., 1997, Effects of ventilation on the compartment enhanced mass loss rate. Proc. Fifth International Sump. On Fire Safety Science, 415-426. Available through: Science Direct Database. [Accessed 12 April 2015] Fleischmann, C. M., and Parkes, A. R., 1997, The Impact of Location and Ventilation on Pool Fire in a Compartment. Proc. Fifth International Sump. On Fire Safety Science, 415-426. Available through: Science Direct Database. [Accessed 12 April 2015] Read More