火焰之輻射熱在火災安全上扮演著相當重要的角色，在過去數十年裡已有不少研究投入於建立熱輻射的模式與實驗。然而，大部份之熱輻射模式並不適用於中、小尺寸之火災，亦即火源之有效直徑小於1 m；且在火焰輻射熱的數值模擬相關研究方面，文獻較缺乏且準確性方面仍有待提升。本研究藉由實驗與數值模擬對於火焰之輻射熱作一驗證，並根據不同之熱源大小(D = 14-38 cm)及熱輻射量測位置進行分析。
在數值模擬方面，根據不同的格點尺寸、光譜波段(spectral bands)與固體角(solid angles)等參數，來尋求在進行數值模擬時之最適化操作條件。在火焰高度方面，經實驗與數值模擬結果之比對，當D*/δx小於13時其火焰高度是隨著縮小格點尺寸而增加；當D*/δx值超過13時，其火焰高度已呈現定值的趨勢。在實驗與數值模擬結果的比對方面，當量測點的高度低於火焰平均高度時，其結果的趨勢有很好的一致性；然而，當量測點的高度超過火焰平均高度時，計算的預測值多已高估了實驗值。其原因在於因燃燒模式的限制，使得火焰面周圍產生的煙量遠多於經實驗觀察的現象，過多的煙量可能導致其有高估的現象。在間歇區火焰之熱輻射方面，經由實驗量測獲得數據後可以發現，當輻射熱量測點置於燃料面的高度時，間歇區火焰所放射之輻射熱約為整體輻射熱值之36%；當量測點升高至火焰平均高度時，間歇區火焰所放射之輻射熱將約為整體輻射熱值之50%。此外，根據實驗結果所建立之熱輻射模式，結果顯示，針對本研究之實驗能獲得不錯之預測值；同時對於熱輻射熱分率之預測結果與實驗值比對，其誤差值約在14%的範圍內。
本研究之最終目的在於修正數值模擬時之不準確度以尋求最佳操作條件，並建立適用於中小尺寸火源之輻射熱經驗式，期望應用於不同火場或初期火災時，能對輻射熱能有更高精確的掌握。

Radiant power from a flame plays an important role for fire safety. Over the last decades, numerous investigations of fires on thermal radiation have been developed by various thermal radiation models, numerical simulations and measurements. However, most of thermal radiation models are not suitable for small to medium sized fires, where the effective diameter of a fire is less than 1 meter. This work investigates the radiation characteristics in simulations and experiments from the heptane liquid pool fires. These small to medium sized pool fires (14-38 cm) were originated for comparison.
The computational fluid dynamics (CFD) approach was used to predict the radiative heat flux for various pool diameters, grid sizes, spectral bands and solid angles. The results show that calculated flame shapes and heights are in good agreement with the measurements, as D*/δx is over 13. In the aspect of thermal radiation, the calculated radiative fluxes located within the height of the continuous flame zone are in good agreement with the measurements, whereas the predictions beyond that level deviate markedly from the experimental results, because the simulated amount of the soot created at the side of flame surface exceeds the experimentally observed volume.
Experimentally, the effect of the intermittency of a flame on thermal radiation was performed. A shield was used to shade the radiant power from a persistent flame, and the radiative flux was measured from an intermittent flame on 30 cm diameter pool fires. The results show that 36 % of the radiative flux measured is emitted from the intermittent flame when the radiometer is located at the base of the pool fire. As the radiometer is moved upwards, the radiative fluxes measured from the intermittent flame increase gradually, even to 50%. Based on the results, the thermal radiation model with oscillation frequency was developed in this work. Measurements made with small to medium-sized pool fires (14-38 cm) were compared with estimates using the model. The results indicate that the predicted radiative fluxes closely correspond to the measurements made at various locations and that the variation of radiative fraction is within 14% as the location of the radiative flux gauge is varied.

1. T. Yumoto, “Fire Spread between Two Oil Tanks,” Journal of Fire and Flammability, 8 (1977) 494.
2. M. Röwekamp, R. Bertrand, F. Bonneval, D. Hamblen, N. Siu, H. Aulamo, J. Martila, J. Sandberg and R. Virolainen, Fire Risk Analysis, Fire Simulation, Fire Spreading and Impact of Smoke and Heat on Instrumentation Electronics, NEA/CSNI/R(99)27, 2000.
3. M. Munoz, J. Arnaldos, J. Casal and E. Planas, Analysis of the Geometric and Radiative Characteristics of Hydrocarbon Pool Fires, Combustion and Flame, 139(3) (2004) 263-277.
4. V. Ho, N. Siu and G. Apostolakis, COMPBRN III—A Fire Hazard Model for Risk Analysis, Fire Safety Journal, 13(3) (1988) 137–154.
5. L.Y. Copper, M. Harkleroad, J. Quintiere and W. Rinkinen, An experimental study of upper hot layer stratification in full-scale multi-room fire scenarios, Journal of Heat Transfer, 104 (1982) 741–749.
6. Y. L. Sinai, Exploratory CFD modelling of pool fire instabilities without cross-wind, Fire Safety Journal, 35(1) (2000) 51–62.
7. G. H. Yeoh, R. K. K. Yuen, S. C. P. Chueng and W. K. Kwok, On modelling combustion, radiation and soot processes in compartment fires, Building and Environment, 38 (2003) 771–785.
8. X. Jiang and K. H. Lou, Combustion-induced buoyancy effects of an axisymmetric reactive plume, Proceedings of the Combustion Institute, 28 (2000) 1989–96.
9. J. X. Wen, K. Kang, T. Donchev and J. M. Karwatzki, Validation of FDS for the prediction of medium-scale pool fires, Fire Safety Journal, 42 (2007) 127–138.
10. B. J. McCaffrey, Purely buoyant diffusion flames: some experimental results, National Bureau of Standards, NBSIR 79-1910, 1979.
11. McGrattan K B, Floyd J E, Forney G P, Baum H R, and Hostikka S (2003) Improved Radiation and Combustion Routines for a Large Eddy Simulation Fire Model. Fire Safety Science, Proceedings of Seventh International Symposium, 827-838.
12. S. Hostikka, K. B. McGrattan, and A. Hamins, Numerical Modeling of Pool Fires Using LES and Finite Volume Method for Radiation, Fire Safety Science, Proceedings of Seventh International Symposium, (2003) 383-394.
13. L. T. Cowley and A. D. Johnson, Oil and Gas Fires: Characteristics and Impact, Health and Safety Executive, UK, 1992.
14. Shokri M and Beyler C L (1989) Radiation from Larger Pool Fires. SFPE Journal of Fire Protection Engineering (4): 141–150.
15. DiNenno P J (1995) The SFPE Handbook of Fire Protection Engineering, 2nd edition, National Fire Protection Association, Massachusetts.
16. A. T. Modak, Thermal Radiation From Pool Fires, Combustion and Flame, 29 (1977) 177–192.
17. Mudan K S (1984) Thermal Radiation Hazards from Hydrocarbon Pool Fires. Progress Energy Combustion Science (10): 59–80.
18. Apte V B (1998) Effect of scale and fuel type on the characteristics of pool fires for fire fighting training. Fire Safety Journal 31(4): 283–298.
19. Chow W K, Li Y Z, Cui E and Huo R (2001) Natural smoke filling in atrium with liquid pool fires up to 1.6 MW. Building and Environment 36(1): 121–127.
20. Heskestad G (2003) Extinction of gas and liquid pool fires with water sprays. Fire Safety Journal 38(4): 301–317.
21. Liu J H, Liao G X, Fan W C, Yao B and Lu X Y (2002) Study of liquid pool fire suppression with water mists by cone calorimeter. Journal of Fire Science 20(6): 465–477.
22. Richard J, Garo J P, Souil J M, Vantelon J P and Lemonnier D (2002) Addition of a water mist on a small-scale liquid pool fire: Effect on radiant heat transfer at the surface. Progress Energy Combustion Science (29): 377–384.
23. Chow W K (1996) Multi-cell concept for simulating fire in big enclosures using a zone model, Journal of Fire Sciences. 14(3): 186–98.
24. Ho V, Siu N and Apostolakis G (1988) COMPBRN III—A Fire Hazard Model for Risk Analysis. Fire Safety Journal 13(3): 137–154.
25. Zukoski E E and Kubota T (1980) Two-Layer Modeling of Smoke Movement in Building Fires. Fire and Materials 4(1): 17-27.
26. Copper LY, Harkleroad M, Quintiere J and Rinkinen W (1982) An experimental study of upper hot layer stratification in full-scale multi-room fire scenarios. Journal of Heat Transfer (104): 741–749.
27. Jiang X and Lou K H (2000) Combustion-induced buoyancy effects of an axisymmetric reactive plume. Proceedings of the Combustion Institute (28): 1989–96.
28. Nam S and Bill R G (1993) Numerical simulation of thermal plumes. Fire Safety Journal (21): 231–56.
29. Wang H Y, Joulain P and Most J M (1999) Modeling on burning of large-scale vertical parallel surfaces with fire-induced flow. Fire Safety Journal (32): 241.
30. Wen J X and Huang L Y (2000) CFD modeling of confined jet fires under ventilation-controlled conditions. Fire Safety Journal (34): 1-24.
31. McGrattan K B, Baum H R and Rehm R G (1998) Large eddy simulations of smoke movement. Fire Safety Journal (30): 161.
32. Zhang W and Chen Q (2000) Large eddy simulation of natural and mixed convection air-flow indoors with two simple filtered dynamic sub-grid scale models. Numerical Heat Transfer (Part A) (37): 447-463.
33. Wang H Y, Coutin M and Most J M (2002) Large-eddy-simulation of buoyancy- driven fire propagation behind a pyrolysis zone along a vertical wall. Fire Safety Journal (37): 259-285.
34. Ma T G and Quintiere J G (2003) Numerical Simulation of an Axi-symmetric Fire Plume: Accuracy and Limitations. Fire Safety Journal (38): 467-492.
35. Grosshandler W L (1993) RADCAL: A Narrow-Band Model for Radiation Calculations in a Combustion Environment, NIST Technical Note 1402, Washington.
36. Hamins A, Klassen M, Gore J and Kashiwagi T (1991) Estimate of Flame Radiance via a Single Location Measurement in Liquid Pool Fires. Combustion and flame (86): 223-228.
37. Drysdale, D., (1999). An Introduction to Fire Dynamics, 2nd edition, New York.
38. B.M. Cetegen, E.E. Zukoski, and T. Kubota, Entrainment and flame geometry of fire plumes, National Bureau of Standards, NBS-GCR-82-402, 7, Washington, 1982.
39. K. Hillm, J. Dreisbach, F. N. Joglar, K. B. McGrattan, R. Peacock and A. Hamins, Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications, NUREG-1824, 7, Washington, 2007.
40. Smagorinsky J (1963) General circulation experiments with primitive equations –I, the basic experiment. Monthly Weather Rev. (91): 99-105.
41. Xin Y (2004) Assessment of Fire Dynamics Simulation for Engineering Applications: Grid and Domain Size Effects. In Proceedings of the Fire Suppression and Detection Research Application Symposium, Orlando, Florida. National Fire Protection Association, Quincy, Massachusetts.
42. McGrattan K B, Floyd J E, Forney G P, Baum H R, and Hostikka S (2003) Improved Radiation and Combustion Routines for a Large Eddy Simulation Fire Model. Fire Safety Science, Proceedings of Seventh International Symposium, 827-838.
43. Hostikka S, McGrattan K B, and Hamins A (2003) Numerical Modeling of Pool Fires Using LES and Finite Volume Method for Radiation. Fire Safety Science, Proceedings of Seventh International Symposium, 383-394.
44. Ma T G and Quintiere J G (2003) Numerical Simulation of an Axi-symmetric Fire Plume: Accuracy and Limitations. Fire Safety Journal (38): 467-492.
40. Hillm K, Dreisbach J, Joglar F N, McGrattan K B, Peacock R and Hamins A (2007) Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications. NUREG-1824 (7), Washington.
45. Yumoto T (1977) Fire Spread between Two Oil Tanks. Journal of Fire and Flammability (8): 494.
46. May W G and McQueen W (1973) Radiation from Large Liquefied Natural Gas Fires. Combustion Science and Technology (7): 51–56.
47. Molina A, Schefer R W and Houf W G (2007) Radiative fraction and optical thickness in large-scale hydrogen-jet fires. Proceedings of the Combustion Institute (31): 2565–2572.
48. John L D, Peter K W and Heskestad G (2000) Radiation fire modeling. Proceedings of the Combustion Institute (28): 2751–2759.
49. Muñoz M, Planas E, Ferrero F and Casal J (2007) Predicting the emissive power of hydrocarbon pool fires. Journal of Hazardous Materials (144): 725–729.
50. David W J and John B C (2007) Modeling the release, spreading, and burning of LNG, LPG, and gasoline on water. Journal of Hazardous Materials (140): 535–540.
51. Fay J A (2006) Model of large pool fires. Journal of Hazardous Materials (136) 219–232.
52. Phani K R (2007) Large hydrocarbon fuel pool fires: Physical characteristics and thermal emission variations with height. Journal of Hazardous Materials (140) 280–292.