The Dynamics of Fires in Various Conditions - Term Paper Example

Name : xxxxxx Tutor : xxxxxxx Title : Fires in inclined trenched – trench effect Institution : xxxxxxx @2016 Abstract This report investigates the dynamics of fires in various conditions. It entails details of the relationship between the rates of fire spread with the slope of the fire surface. The report also gives details of the methodology used to establish the relationship. Results collected from the experiments are also included in the report. Introduction Fire break out is one of the most dangerous catastrophes that have been known to leave fatal causalities. Control and containment of such fires especially of higher magnitude is normally difficult considering the fact that they always happen in unpredictable pattern and in unpredictable locations (Rothermel, 1966). Most of the experiments performed by various scholars within the field of engineering and fire safety reveal that, there is a significant increase in fire spread at an inclined surface as compared to the flat surfaces. Australian bush fire fighters have established based on their experiences that the rate of spread of bushfires doubles for every increase in the slope of the fire surface by 10ºC. The King`s Cross fire and the trench effect Most of the fire dynamics and all the preceding investigation on its behavior are based on the fire effect experienced at the King`s cross underground station in the year 1987. Before then, limited information existed on the exact or actual behavior of flames within a limited and inclined enclosure. After the incident and as a result of public demand as to the reason why little was done to salvage the impending catastrophe, a report was published after investigations and this was a real basis for the phenomenon of spread of fires on inclined surfaces (Rothermel, 1966). The fire at the King`s station was interpret as a result of confinement of flames within the escalator trench. This provided an inclined surface that led to rapid fire spread along the escalator and subsequent spread to the surrounding. The figure below helps to describe the phenomena of spread of fires both on a level and on an inclined surface (Heras, 2008). INCLUDEPICTURE "http://www.physics.ucsb.edu/~complex/research/hfire/fbehave/images/slope_tilt.gif" \* MERGEFORMATINET Figure 1: Fire spread on a flat and sloppy surface Aims of the experiment The experiment is designed to achieve the following objectives; Demonstrate the fire spread in varying slope inclinations. Determine the relationship between the rates of fire spread and slope. Obtain empirical data to help in proving the phenomenon of trench effect in fire spread. Hypothesis The rate of fire spread are known to vary depending on the angle of inclination of the fire surface. Therefore, as the angle of inclination increases, the rate of fire spread also increases up to some limit (Heras, 2008). Methodology Apparatus Apparatus Description Test Trench 2440mm long, 270mm wide & 200mm high Inclinometer Minimum Range (0ºC to 40 ºC) Fuel Corrugated cardboard (Adhesive or paint free) Thermocouples 1500 ºC temperature resistance Data logger Data collection, printout or display capabilities Table 1: The Apparatus for fire trench experiment Method The angle of inclination of the trench was measured and recorded using an inclinometer. The height of the roof of the trench was also measured by use of a meter rule and the result recorded and kept. The card board was then placed on the trench in a manner that it rested on top of aluminum support and flushed with the lower edge of the trench. The side with the distance markets was placed to face the up position. The card board was then secured in place and the location of the thermocouples along the board determined. The data logger was then started, the bottom edge of the card board ignited and full width of the card board ensured that it is ignited too. When the flame frost reached 00mm mark, timing of the rate of fire spread was started. The inclination of the plane was reduced from 30ºC by 10 ºC and similar procedure repeated until when trench effect was no longer observed. The test was repeated at an inclination of 30 ºC with a fan blowing across the opening of the tunnel. Similar procedure was also repeated with a fan blowing up the length of the tunnel. The results were recorded. Results Height of the roof of the trench = 200mm Length of the flame = 2440mm The tables below summarized the results collected into a simple form. i) At 30ºC Upwards with a fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C             0 67.15 45.76 40.02 26.7 40.45 10 66.74 45.1 39.7 27.67 39.07 20 66.48 44.49 40.92 29.29 37.19 30 88.32 53.52 42.85 32.51 55.81 40 111.86 74.48 44.91 36.13 75.73 50 125.73 161.03 59.16 38.99 122.04 100 284.75 415.22 168.83 113 302.22 150 330.87 313.79 529.31 175.77 353.54 173 389.29 471.32 211.68 79.68 391.64 Table 2: Results with a fan with maximum inclination ii) At 20 ºC without a fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C             0 105.7 74.9 51.3 36.1 69.6 10 105.2 74.4 51.6 37.1 68.0 20 115.5 79.4 54.6 37.7 77.8 30 118.3 84.3 57.0 38.8 79.5 40 122.0 107.6 60.9 40.6 81.4 50 125.4 129.5 74.1 41.7 87.8 100 281.1 376.9 319.6 108.7 268.2 150 164.0 433.6 515.6 264.3 351.6 180 146.4 251.1 346.8 155.5 200.5 Table 3: At 20 degrees inclination without a fan iii) Zero degrees without a fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C             0 73.2 36.3 46.3 23.2 50.1 10 73.4 38.0 48.7 23.3 50.1 20 73.6 39.6 50.8 23.2 50.4 30 73.6 41.1 52.8 23.1 50.5 40 73.5 42.4 54.4 22.9 50.7 50 73.5 43.6 55.8 22.8 50.7 100 73.0 47.8 59.9 23.2 49.9 150 72.0 49.7 61.2 22.9 49.1 206 70.9 51.0 60.4 22.8 48.1 Table 4: Flat surface with no fan iv) 10ºC no fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C   0 92.6 61.1 64.6 40.2 50.1 10 91.9 58.6 62.5 40.4 50.1 20 92.6 62.1 66.6 35.9 50.4 30 92.7 67.0 70.9 33.0 50.5 40 92.6 70.2 73.3 31.7 50.7 50 92.5 72.5 74.9 30.8 50.7 100 90.7 77.7 78.0 28.9 49.9 150 103.9 78.5 78.0 27.2 49.1 206 274.3 278.0 107.9 25.9 48.1 Table 5: 10 degrees with no fan v) 30 degrees with a cross fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C   0 60.3 44.9 39.5 27.0 33.3 10 60.0 42.7 38.1 28.7 31.3 20 60.4 43.9 40.9 30.8 29.6 30 76.4 60.1 42.9 33.5 42.9 40 83.0 185.5 59.9 36.2 149.3 50 93.4 204.3 201.8 42.2 162.1 100 262.3 378.0 286.5 126.1 251.9 150 131.5 101.1 70.3 44.1 87.4 206 106.6 70.7 50.4 32.1 74.5 Table 6: 30 degree with a cross fan vi) 30 degrees with no fan Time TC 1 TC 2 TC 3 TC 4 Temp Diff Seconds °C °C °C °C °C   0 17.8 17.8 17.6 17.7 0.2 10 17.8 17.8 17.7 18.2 0.5 20 17.8 17.8 17.7 18.6 1.0 30 17.9 17.8 17.7 19.1 1.5 40 17.9 17.8 17.7 19.3 1.6 50 17.9 17.9 17.8 19.5 1.7 100 18.0 18.0 17.9 19.0 1.0 150 18.1 18.0 18.0 18.4 0.5 206 18.3 18.1 18.0 18.7 0.7 Table 7: 30 degrees with no fan Discussion From the results obtained above, the following curves were obtained. i) For 30 ºC with an upwards fan The fire spread is not significant as shown in the graph. ii) At 20ºC without a fan The fire spread was significant especially at thermocouple 3 with temperetures going beyond 600ºC. Therefore at an inclination of 20 ºC with no air flow, burning is significant as compared to fire spread at 30 ºC with a fan blowing iii) 0ºC with no fan On a flat surface with no airflow, the rate of fire spread is not as significant as at 20ºC surface inclination with no airflow. The highest temperature recorded by thermocouple 3 was approximately 250. iv) 10ºC no fan All the thermocouples recorded high temperatures. There is a significant rate of fire spread as recorded by thermocouples. v) 30ºC cross fan A significant rate of fire spread is recorded by all the thermocouples. The fire spread is rapid and is noticeable within the first few seconds of the experiment. vi) 30ºC no fan The angle of inclination above is considered as tending towards the limit. The fire spread as seen from the graphs is significantly reduced. Effect of inclination on fire spread and temperatures As seen from the graphs above, it is evident that as the angle of inclination is increased, the rate of fire spread significantly increases up to an inclination of 30ºC when the rate starts to reduce. Moreover, the increase in the angle of inclination of the slope results in an increase in temperature of the fire. The graphs obtained from the experiments proves that the interpretation that fire spread and temperature of the fire is dependent on the angle of inclination of the surface is true. Effect of air flow in fire spread The graphs shown above shows that air flow results in increased fire spread with reduced temperature of the fire. Air flow increases the rate of fire spread but does not affect the temperature of the fire. Team Rules Caution should be observed at all times while handling the equipment. The procedure should be carried out in presence of all the fire safety gear. The observation of the test should be undertaken at some distance from the fire, Conclusion The rate of fire spread varies directly with the angle of inclination up to some limit practical found to be 30ºC. Temperature of the fire increases with an increase in angle of inclination. Air flow increases the rate of fire spread significantly. Works cited ROTHERMEL, R. C., & ANDERSON, H. E. (1966). Fire spread characteristics determined in the laboratory. http://purl.fdlp.gov/GPO/gpo36907. INGASON, H., LI, Y. Z., & LÖNNERMARK, A. (2014). Tunnel fire dynamics. http://public.eblib.com/choice/publicfullrecord.aspx?p=1964981. ROTHERMEL R.C, A. H. (1966). FIRE SPREAD CHARACTERISTICS DETERMINED IN THE LABORATORY. INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION, UTAH: RESEARCH PAPER. HERAS IBÁÑEZ, J. D. L. (2008). Modelling, monitoring and management of forest fires. Southampton, WIT Press. Read More