Cone Calorimeter- Energy Transfer and Thermodynamics - Article Example

Title: Cone calorimeter- Energy transfer and Thermodynamics Introduction A cone calorimeter is a modern device that is used for the burning of samples of different materials and together relevant information relating to the combustion products, release of heat and other disciplines as are associated with the combustion process. The device is widely used in the field of fire safety engineering regarding the mass loss, ignition time, heat release rate, combustion product along with other parameters as are associated with the burning properties of the materials. The device usually permits the fuel samples to expose to the different heat fluxes through the Hogget's principle that describes that the grass heat of combustion of any organic material is directly proportional to the amount of oxygen required for the combustion process (Hugget, 1980)1. The principle of oxygen calorimetry is applied for the measurement of heat through the cone calorimeter (Babrauskas and Peacock, 1992). The device is basically used to determine different properties of fire like, the rate of heat release per unit area, effective heat combustion, cumulative heat released, and time to ignition, mass loss rate, smoke obstruction and total mass loss during the process of combustion. (Blomqvist and Rosell, 2004). The name of the device comes from the conical shape of the radiant heater that usually produces a uniform heat flux over the surface of the sample under study through the cone hoods as with the utilization of the cone calorimeters. Heat flux is also called as thermal flux is the heat flux density or heat flow rate intensity which is a flow of energy per unit area of time and in SI units its units are W·m-2·s-2 and is only measured with the help of cone calorimeter. The results of the experiments have been drawn with the use of blue carpets, green carpet sample and underlay samples. A diagram of the cone calorimeter is attached at annex –A. Results of the Experiment with the Blue Carpet Samples A blue carpet sample of with a mass of 21.966g, surface area as 100 centimeter square with a thickness of 8mm has shown a heat flux of 25kW/m2. The test was lasted for 490 seconds for first blue carpet, 370 seconds for second blue carpet, 710 seconds for third blue carpet and 450 seconds for fourth blue carpet. The results as were recorded are summarized below: Parameters tested First blue carpet Second blue carpet Third blue carpet Fourth blue carpet. Sample of mass 21.966g 17.60g 25.1g 27.8g Surface area 100cm2 100cm2 100cm2 100cm2 Thickness 8mm 8mm 8mm 8mm Heat flux of the experiment 25kW/m2 35kW/m2 45kW/m2 55kW/m2 Time of test 490 seconds 370 seconds 710 seconds 450 seconds Total heat evolved 45.5MJ/m2 34.3MJ/m2 39.4MJ/m2 38.8MJ/m2 Total amount of oxygen consumed 31.6g 24.5g 27.3g 27.2g Smoke released 650m2/m2 472m2/m2 449.7m2/m2 736.5m2/m2 Mass lost during the experiment 12g 13.1g 12.6g 13.4g Specific mass loss rate 2.80g/m2s 5.10g/m2s 1.84g/m2s 3.1g/m2s Average heat release 109kW/m2 103.50kW/m2 57.35kW/m2 87.98kW/m2 Effective heat of combustion 38.88MJ/Kg 20.90MJ/Kg 31.45MJ/Kg 28.87MJ/Kg Mass loss rate 0.030g/sec 0.053g/sec 0.020g/sec 0.031g/sec Specific extinction area 494.86m2/kg 204.50m2/kg 180.14m2/kg 506.13m2/kg Carbon monoxide yield 0.0195Kg/kg 0.0150Kg/kg 0.0128Kg/kg 0.0172Kg/kg Carbon dioxide yield 2.06Kg/kg 1.23Kg/kg 1.70Kg/kg 1.67Kg/kg These results have shown that the average heat release rate has been recorded as 57.35kW/m2 as the minimum heat release rate and 109kW/m2 as the maximum heat release rate for the first blue carpet. The total amount of oxygen as consumed during the combustion process has demonstrated 31.6 g for the first blue carpet as the highest amount of oxygen as was used during the experiment and 24.5 g as the lowest amount of oxygen consumed during the process. However, the amount of mass lost during the experiment does not correspond with the amount of oxygen consumed for the blue carpets as the results have demonstrated 13.4g for the fourth blue carpet whereas the results would have to be on the higher side for the 1st blue carpet where the oxygen combustion was the highest that is 31.6g. The high average mass loss during the experiment as remained 13.4g was probably due to small sample weights that was used in the experiment as 17.60g as the minimum and 27.8g as the maximum sample mass (Blomqvist and Rosell, 2004). Total heat evolved as 34.3MJ/m2 as the minimum heat evolved for the second blue carpet and 45.5MJ/m2 as the maximum heat evolved first blue carpet has demonstrated partial results as in their correct format as was expected in relation to the oxygen used and partial as a deviation from the expected result as for the second blue carpet. All of the remaining values have followed a similar pattern that of oxygen consumption and heat release for the first, second, third and fourth blue carpets. The results of experiment with the green carpet samples for the first, second, third and fourth carpets are summarized as under: Parameters tested First green carpet Second green carpet Third green carpet Fourth green carpet. Sample of mass 13.70g 12.97g 12.67g 12.19g Surface area 100cm2 100cm2 100cm2 100cm2 Thickness 5.5mm 5.5mm 5.5mm 5.5mm Heat flux of the experiment 25kW/m2 35kW/m2 45kW/m2 55kW/m2 Time of test 498seconds 282seconds 266seconds 462seconds Total heat evolved 26.1MJ/m2 - 309.9MJ/m2 28.4MJ/m2 Total amount of oxygen consumed 18.8g - -1174.9g 22g Smoke released 393.8m2/m2 - 486.4m2/m2 517.9m2/m2 Mass lost during the experiment 10g - 8.3g 9.8g Specific mass loss rate 2.48g/m2s - 3.27g/m2s 2.13g/m2s Average heat release 57.56kW/m2 - 1237.38kW/m2 62.4kW/m2 Effective heat of combustion 23.12MJ/Kg - 380.68MJ/Kg 29.24MJ/Kg Mass loss rate 0.027g/sec - 0.35g/sec 0.022g/sec Specific extinction area 131.73m2/kg - 549.72m2/kg 424.2m2/kg Carbon monoxide yield 0.0142Kg/kg - 0.0241Kg/kg 0.024Kg/kg Carbon dioxide yield 1.54Kg/kg - 1.92Kg/kg 1.70Kg/kg At 35kW/m2 heat flux with sample size of 12.97 g for second green carpet no results were recorded and at 45 kW/m2, erroneous results were found for the third green carpet sample. The above mentioned results only could be compared for the 1st and 4th green carpet samples. The amount of oxygen consumed during the combustion process for the 1st and 4th green carpet as correctly demonstrated the results as have been envisaged for their combustion as through the Hugget's principle of oxygen calorimetry. All the values for 55Kw/m2 were high as total heat evolved, total amount of oxygen consumed, smoke released, average heat released, effective heat of consumption, carbon monoxide and carbon dioxide yields for the fourth green carpet sample as compared to that of first green carpet sample, however, mass lost during the experiment remained 10g for the 1st green carpet as compared to that of the 4th green carpet as at the level of 9.8g. Similarly, specific extinction area also remained on the higher side for the fourth green carpet sample as compared to that of the 1st green carpet sample. The specific extinction area for the 4th green carpet sample remained approximately four times higher as compared to that of the 1st green carpet sample during the experiment. Parameters tested First underlay sample Second underlay sample Third underlay sample Fourth underlay sample Sample of mass 10.45g 11.67g 12.14g 16.12g Surface area 100cm2 100cm2 100cm2 100cm2 Thickness 10mm 10mm 10mm 10mm Heat flux of the experiment 45kW/m2 25kW/m2 35kW/m2 55kW/m2 Time of test 143 seconds 228 seconds 307 seconds 250 seconds Total heat evolved 16.6 MJ/m2 16.43MJ/m2 18.4MJ/m2 24.12 MJ/m2 Total amount of oxygen consumed 12.3g 12.01g 9.54g 17.2g Smoke released 650m2/m2 472m2/m2 449.7m2/m2 736.5m2/m2 Mass lost during the experiment 12g 13.1g 12.6g 13.4g Specific mass loss rate 8.56g/m2s 6.84/m2s 3.32 g/m2s 22.09g/m2s Average heat release 117.9kW/m2 75.31kW/m2 61.67kW/m2 99.98kW/m2 Effective heat of combustion 13.76 MJ/Kg 10.90MJ/Kg 19.45MJ/Kg 4.42 MJ/Kg Mass loss rate 0.085g/sec 0.067g/sec 0.032g/sec 0.221g/sec Specific extinction area 337.86m2/kg 155.8 m2/kg 221.64m2/kg 103.43m2/kg Carbon monoxide yield 0.0281Kg/kg 0.0128Kg/kg 0.066Kg/kg 0.0096Kg/kg Carbon dioxide yield 1.06Kg/kg 0.76Kg/kg 1.45Kg/kg 0.36Kg/kg During the experiment, reliable values were recorded for 35kW/m2 that is for third underlay carpet whereas in case of 45kW/m2 flux, all the values were reduced to zero in 4 minutes time. Similarly, all the values were reduced to zero within a period of 5 minutes in 25 kW/m2 flux. The oxygen consumption remained highest for fourth underlay sample that is 17.2g and lowest for the 3rd underlay sample that is at the level of 9.54g. However, average heat of release for 1st underlay carpet remained the highest at the level of 117.9kW/m2 and minimum as for 3rd underlay carpet as at the level of 61.67kW/m2. The non confirmation of results as a direct proportion of the oxygen utilized during the combustion process in case of 3rd underlay samples is reflective of the position which has a support of a low mass as at the level of 9.54g as minimum for the 3rd underlay carpet and highest as 17.2g as for the 4th underlay carpet (Blomqvist and Rosell, 2004). The heat of combustion remained very low for 55 kW/m2 as compared to other heat fluxes that is for 25 kW/m2 , 35 kW/m2 and 45 kW/m2 heat fluxes. Mass loss rate remained highest for 4th underlay carpet that is 0.221g/sec and lowest for the 3rd underlay carpet sample as at the level of 0.032g/sec. However, the position for carbon monoxide and for carbon dioxide remained steady for 35 kW/m2 at all time intervals for the 1st, 2nd, 3rd and 4th underlay carpet samples. Conclusion: As the sample sizes taken for the blue, green and underlay carpets were different for the different materials as used in the experiments as conducted for the study of combustion process and the amount of heat released during the process for its determination through the cone calorimeter. It can safely be concluded that the amount of oxygen consumed is a good indicator for measuring the amount of heat released during the process with all other heat properties including loss of heat released and mass lost due to experiment. The highest average mass lost remained highest for the underlay carpets whereas heat release rate and heat of combustion remained highest for the blue carpet samples as have been recorded during their combustion process and the measurement of heat releases through the cone calorimeter. References: 1. Clark, John, O.E. (2004). The Essential Dictionary of Science. Barnes & Noble Books. ISBN 0-7607-4616-8. OCLC 58732844 63473130. 2.  Van Ness, H.C. (1969). Understanding Thermodynamics. Dover Publications, Inc... ISBN 0-486-63277-6. OCLC 8846081. 3.  Smith, J.M.; Van Ness, H.C., Abbott, M.M. (2005). Introduction to Chemical Engineering Thermodynamics. McGraw Hill. ISBN 0-07-310445-0. OCLC 56491111. 4.  Kelvin, William T. (1849) "An Account of Carnot's Theory of the Motive Power of Heat - with Numerical Results Deduced from Regnault's Experiments on Steam." Transactions of the Edinburg Royal Society, XVI. January 2. Scanned Copy 5. Babrauskas V and Peacock RD. (1992). Heat release rate: the single most important variable in the fire hazrd. Fire safety journal; 18:255-372. Annex-A Read More