THERMAL SCIENCE

International Scientific Journal

TEMPERATURE OF GASES IN A TRACE OF WATER DROPLETS DURING THEIR MOTION IN A FLAME

ABSTRACT
The paper experimentally investigates the integral characteristics of the processes involved in the reduction of gas temperature by injecting the aerosol flow of water droplets into a counter flow of combustion products (period of steady low gas temperature Tg’ compared to the initial Tg, range of temperature decrease (ΔTg=Tg-Tg’), rate of temperature recovery, the geometric dimensions of the temperature traces and their lifetime). We use the following recording devices: fast-response thermocouples (heat inertia less than 0.1 s), a multichannel recorder, a high-speed video camera (up to 105 frames per second), as well as a cross-correlation hardware and software package (with optical methods for recording the front and trace of the aerosol). The temperature trace of an aerosol is defined as the area with the temperature Tg’ lower than the initial Tg by at least 10 K. We determine how the following group of factors affects the characteristics of temperature traces of water droplets: size (0.04-0.4 mm) and concentrations (3•10-5-11•10-5 m3 of droplet/m3 of gas) of droplets in a pulse, the initial temperature of water (280-340 K), the duration of a pulse (1-5 s), the temperature (350-950 K) and velocities (0.5-5 m/s) of combustion products. The temperature in a trace of water droplets during their motion in a flame can be reduced due to rapid vaporization or heat exchange between the gases and water. The conditions are identified, under which the low temperature of gases in a trace of droplet aerosol can be preserved for a long time (20-30 s). Finally, we forecast the parameters of temperature traces under the conditions of actual fires with combustion product temperatures over 1000 K.
KEYWORDS
PAPER SUBMITTED: 2016-03-02
PAPER REVISED: 2017-02-17
PAPER ACCEPTED: 2017-02-17
PUBLISHED ONLINE: 2017-03-03
DOI REFERENCE: https://doi.org/10.2298/TSCI160302020V
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2018, VOLUME 22, ISSUE Issue 1, PAGES [335 - 346]
REFERENCES
  1. Xiao, X.K., et al., On the Behavior of Flame Expansion in Pool Fire Extinguishment with Steam Jet, Journal of Fire Sciences, 29 (2011), 4, pp. 339-360
  2. Tang, Z., et al., Experimental Study of the Downward Displacement of Fire-induced Smoke by Water Spray, Fire Safety Journal, 55 (2013), pp. 35-49
  3. Vysokomornaya, O.V., et al., Experimental investigation of atomized water droplet initial parameters influence on evaporation intensity in flaming combustion zone, Fire Safety Journal, 70 (2014), pp. 61-70
  4. McAllister, S., Critical mass flux for flaming ignition of wet wood, Fire Safety Journal, 61 (2013), pp. 200-206
  5. Korobeinichev, O.P., et al, Fire suppression by low-volatile chemically active fire suppressants using aerosol technology, Fire Safety Journal, 51 (2012), pp. 102-109
  6. Joseph, P., et al, A comparative study of the effects of chemical additives on the suppression efficiency of water mist, Fire Safety Journal, 58 (2013), pp. 221-225
  7. Yoshida, A., et al, Experimental study of suppressing effect of fine water droplets on propane/air premixed flames stabilized in the stagnation flow field, Fire Safety Journal, 58 (2013), pp. 84-91
  8. Volkov, R.S., et al., The influence of initial sizes and velocities of water droplets on transfer characteristics at high-temperature gas flow, International Journal of Heat and Mass Transfer, 79 (2014), pp. 838-845
  9. Volkov, R.S., et al., Experimental investigation of mixtures and foreign inclusions in water droplets influence on integral characteristics of their evaporation during motion through high-temperature gas area, International Journal of Thermal Sciences, 88 (2015), pp. 193-200
  10. Glushkov, D.O., et al., Experimental Investigation of Evaporation Enhancement for Water Droplet containing Solid Particles in Flaming Combustion Area, Thermal Science, doi:10.2298/TSCI140901005G
  11. Strizhak, P.A., Influence of droplet distribution in a "water slug" on the temperature and concentration of combustion products in its wake, Journal of Engineering Physics and Thermophysics, 86 (2013), 4, pp. 895-904
  12. Kuznetsov, G.V., Strizhak, P.A., Numerical investigation of the influence of convection in a mixture of combustion products on the integral characteristics of the evaporation of a finely atomized water drop, Journal of Engineering Physics and Thermophysics, 87 (2014), 1, pp. 103-111
  13. Kuznetsov, G.V., Strizhak, P.A., Influence of volume concentration of water droplet aggregation at their moving through high-temperature gases on temperature in a trace, Journal of Applied Mechanics and Technical Physics, 56 (2015), 4, pp. 1-13
  14. Keane, R.D., Adrian, R.J., Theory of cross-correlation analysis of PIV images, Applied Scientific Research, 49 (1992), pp. 191-215
  15. Westerweel, J., Fundamentals of digital particle image velocimetry, Measurement Science and Technology, 8 (1997), pp. 1379-1392
  16. Dehaeck, S., et al., Laser marked shadowgraphy: a novel optical planar technique for the study of microbubbles and droplets, Experiments in Fluids, 47 (2009), 2, pp. 333-341
  17. Akhmetbekov, Y.K., et al., Planar fluorescence for round bubble imaging and its application for the study of an axisymmetric two-phase jet, Experiments in Fluids, 48 (2010), 4, pp. 615-629
  18. Volkov, R.S., et al., Influence of droplet concentration on evaporation in a high-temperature gas, International Journal of Heat and Mass Transfer, 96 (2016), pp. 20-28
  19. Volkov, R.S., et al., Experimental investigation of consecutive water droplets falling down through high-temperature gas zone, International Journal of Heat and Mass Transfer, 95 (2016), pp. 184-197
  20. Glushkov, D.O., et al., Influence of radiative heat and mass transfer mechanism in system water droplet high-temperature gases on integral characteristics of liquid evaporation, Thermal Science, 15 (2015), 5, pp. 1541-1552
  21. Grishin, A.M., et al., Comparative analysis of thermokinetic constant of drying and pyrolysis of forest fuels, Combustion and Explosion Physics J., 27 (1991), pp. 17-24
  22. Lautenberger, C.H., Fernando-Pello, C.A., A model for the oxidative pyrolysis of wood, Combustion and Flame, 156 (2009), pp. 1503-1513

© 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence