EXPERIMENTAL STUDY OF A WATER-MIST JET ISSUING NORMAL TO A HEATED FLAT PLATE

Abstract

A parametric experimental study on the development of a round jet spray impacting a smooth, heated, flat plate has been accomplished. The main objective of this effort was to provide information characterizing the flow structure of a developing mist jet, issuing vertically towards an upward facing, horizontal heated plate, by means of simultaneous droplet size and velocity measurements. Phase Doppler Anemometry was used, providing also information on liquid volume flux. The fine spray of small atomized droplets (0.5-5.0 μm), was generated using a medical nebulizer. Two low Reynolds number jets (Re=2952, 3773) issuing from a cylindrical pipe have been tested. The distance between the jets' exit and the plate was 50 cm. A stainless steel non-magnetic flat plate of dimensions 1000x500x12mm3 was used as target wall. Constant heat flux boundary conditions were established during measurements. Results indicate that the heat flux from the plate is influencing the evolution of the spray jet, diminishing its velocity and turbulence. Average droplet sizes are affected little by the heat flux, although for the non-heated sprays, droplet sizes increase at locations very close to the plate. A significant effect on droplet volume flow rate is also reported.

Keywords

Dates

  • Submission Date2013-05-14
  • Revision Date2013-06-17
  • Acceptance Date2013-10-04
  • Online Date2013-11-16

DOI Reference

10.2298/TSCI130514149V

References

  1. Jia, W., Qiu, H.-H., Experimental Investigation of Droplet Dynamics and Heat Transfer in Spray Cooling, Exp. Thermal and Fluid Science, 27 (2003), pp. 829-838
  2. Grissom, W.M., Wierum, F.A., Liquid spray cooling of a heated surface, Int. J. Heat Mass Transfer, 24 (1981), pp. 261-271
  3. Qiao, Y.M., Chandra, S., Spray cooling enhancement by addition of a surfactant, ASME J. Heat Transfer, 120 (1998), pp. 92-98
  4. Yao, S.C., Choi, K.J., Heat transfer experiments of mono-dispersed vertically impacting sprays, Int. J. Multiphase Flow, 13 (1987), 5, pp. 639-648
  5. Zhang, S., Gogos, G., Film evaporation of a spherical droplet over a hot surface: fluid mechanics and heat/mass transfer analysis J. Fluid Mechanics, 222 (1991), pp. 543-563
  6. Horacek, Β., Kiger, K.T., Kim, J., Single Nozzle Spray Cooling Heat Transfer Mechanisms, Int. J. Heat Mass Transfer, 48 (2005), pp. 1425-1438
  7. Lin, L., Ponnappan, R., Heat transfer characteristics of spray cooling in a closed loop, Int. J. Heat Mass Transfer, 46 (2003), 20, pp. 3737-3746
  8. Gonzalez, J.E., Black, W.Z., Study of Droplet Sprays prior to Impact on a Heated Horizontal Surface, ASME J. Heat Transfer, 119 (1997), pp. 279-287
  9. Cossali, G. E., Marengo, M., Santini, M., Thermally Induced Secondary Drop Atomization by Single Drop Impact onto Heated Surfaces, Int. J. Heat Fluid Flow, 29 (2008), pp. 167-177
  10. Bernardin, J.D., Stebbins, C.J., Mudawar, I., Mapping of impact and heat transfer regimes of water drops impinging on a polished surface, Int. J. Heat Mass Transfer, 40 (1997), 2, 247-267
  11. Chandra, S., Avedisian, C.T., On the collision of a droplet with a solid surface, Proc. Royal Soc., 42 (1991), pp. 13-41
  12. Chaves, H., Kubitzek, A.M., Obermeier, F., Dynamic processes occurring during the spreading of thin liquid films produced by drop impact on hot walls, Int. J. Heat Fluid Flow 20, (1999), pp. 470-476
  13. Di Marzo, M., Tartarini, P., Liao, Y., Evans, D., Baum, H., Evaporative cooling due to a gently deposited droplet, Int. J. Heat Mass Transfer, 36 (1993), 17, pp. 4133-4139
  14. Ko, Y.S., Chung, S.H., An experiment on the break-up of impinging droplets on a hot surface, Exp. Fluids, 21 (1996), pp. 151 - 173
  15. Yoshida, K., Abe, Y., Oka, T. Mori, Y.H., Nagashima, A., Spray Cooling under Reduced Gravity Conditions. ASME J. Heat Transfer, 123 (2001), pp. 309-318
  16. Kim, J., Spray Cooling Heat Transfer: The State of the Art, Int. J. Heat Fluid Flow, 28 (2007), pp. 753-767
  17. Vouros, A., Panidis, Th., Statistical Analysis of Turbulent Thermal Free Convection over a Horizontal Heated Plate in an Open Top Cavity, Exp. Thermal and Fluid Science, 36 (2012), pp. 44-55
  18. Tate, R.W., Some Problems Associated with the Accurate Representation of Droplet Size Distributions. In Proceedings of the Second International Conference on Liquid Atomic and Spray Systems, Madison, 1982
  19. Hardaloupas, Y., Taylor, A.M.K.P, Witelaw, J.H., Mass Flux, Mass Fraction and Concentration of Liquid Fuel in a Swirl - Stabilized Flame, Int. J. Multiphase Flow, 20 (1994), pp. 233-259
  20. Tropea, C., Xu, T-H., Onofri, F., Grehan, G. Haugen, P., Stieglmeier, M.Dual - Mode Phase - Doppler Anemometer, Part. Particle & Particle Systems Characterization, 13 (1996), pp. 165-170
  21. Widmann, J.F., Presser, C., Leigh, S.D., Improving Phase Doppler Volume Flux Measurements in Low Data Rate Applications, Measurement Science and Technology, 12 (2001), pp. 1180-1190
  22. Saffman, M. Automatic Calibration of LDA Measurement Volume Size, Applied Optics, 26 (1987), pp. 2592-2597
  23. Lefebvre, A.H., Atomization and Sprays, Τaylor & Francis Hemisphere, USA, 1989
  24. Zhou, Z., Wu, W., Chen, B., Wang, G., Guo, L., An Experimental Study on the Spray and Thermal Characteristics of R134a Two-Phase Flashing Spray, Int. J. Heat Mass Transfer 55, (2012), pp. 4460-4468
  25. Moita, A.S., Moreira, A.L.N., Drop Impacts onto Cold and Heated Rigid Surfaces: Morphological Comparisons, Disintegration Limits and Secondary Atomization, Int. J. Heat Fluid Flow 28 (2007), pp. 735-752