OPEN ACCESS
Water droplets emitted from cooling towers must be prevented for several reasons, human health hazards are the most important ones. The generation and control of these droplets are the main tasks for drift eliminators: devices installed inside mechanical draft cooling towers useful to prevent water droplets, originated by the crossflow between air and water inside the tower, from being released into the environment. This is the phenomenon called ‘drift’. In this paper, the operating conditions of a type of drift eliminator placed in a cooling tower are studied. This work is focused on the numerical and experimental characterization of the multiphase flow taking place when water droplets, drifted by the airstream, impact on the water film formed over the drift eliminators plates. The problem of these drop impacts has been studied throughout an experimental installation and a numerical model has been developed throughout the ANSYS software and several VOF multiphase flow simulations have been carried out showing a good agreement with experimental data.
CFD, cooling tower, drift eliminator, drop impact, water film
[1] Lucas, M., Ruiz, J., Martinez, M.J., Kaiser, A.S., Viedma, A. & Zamora, B., Experimental study on the performance of a mechanical cooling tower fitted with different types of water distribution systems and drift eliminators. Appl. Therm. Eng. 50, pp. 282–292, 2013. doi: http://dx.doi.org/10.1016/j.applthermaleng.2012.06.030
[2] Zamora, B. & Kaiser, A.S., Simulación numérica del flujo turbulento de aire con gotas dispersas de agua a través de separadores de torres de refrigeración. Rev. Int. Mét. Num. Cálculo Diseño Ingen. 28, pp. 148–160, 2012.
[3] Sikalo, S., Tropea, C. & Ganic, E.N., Impact of droplets onto inclined surfaces. J. Colloid Interface Sci. 286, pp. 661–669, 2005. doi: http://dx.doi.org/10.1016/j.jcis.2005.01.050
[4] Nikolopoulos, N., Theodorakakos, A. & Bergeles, G., Normal impingement of a droplet onto a wall film: a numerical investigation. Int. J. Heat Fluid Flow 26, pp. 119–132, 2005. doi: http://dx.doi.org/10.1016/j.ijheatfluidflow.2004.06.002
[5] Lunkad, S.F., Buwa, V.V. & Nigam, K.D.P., Numerical simulations of drop impact and spreading on horizontal and inclined surfaces. Chem. Eng. Sci. 62, pp. 7214–7224, 2007. doi: http://dx.doi.org/10.1016/j.ces.2007.07.036
[6] Arienti, M., Wang, L., Corn, M., Li, X., Soteriu, M.C., Shedd, T.A. & Herrmann, M., Modelling wall film formation and breakup using an integrated interface-tracking/discrete-phase approach. ASME Turbo Expo 2010: Power for Land, Sea, and Air, Glasgow, UK, 2010.
[7] Guide to the Expression of Uncertainty in Measurement, International Standard Organization, 1995.
[8] Lan, H., Friedrich, M. & Armaly, B.F., Simulation and measurement of 3D shear-driven thin liquid film in a duct. Int. J. Heat Fluid Flow 29, pp. 449–459, 2008. doi: http://dx.doi.org/10.1016/j.ijheatfluidflow.2007.12.003
[9] ANSYS, Inc., Ansys Fluent 14 Theory Guide, ANSYS, Inc., 2012.