Experimental Characterization of Liquid Flows in Cooling Tower Packing

Wet cooling towers are used in many industrial processes. Although the heat transfer phenomena have been well studied in this kind of towers, the hydrodynamic behavior of air–water counter flows in industrial cooling tower packings remains unknown and has never been studied with local experimental approaches. Hydrodynamics are directly linked with operating issues such as packing fouling reducing cooling efficiency, or circuit operating optimization conditions that have an impact on the industrial plants' performances. The objective of this work is to develop representative tools to understand and characterize liquid/air flow inside industrial cooling tower packings. In order to study the hydrodynamic characteristics of liquid/gas flows in a widely deployed industrial packing, a pilot-scale experimental cooling tower has been designed, built, and operated. The experiments allowed the visualization of a falling water film along the packing sheets. Specific methods have been developed to measure main flow parameters such as the water film thickness and the packing wetting rate depending on the operating air and water conditions. The contrast method allows the measurement of water film thickness with time around several hundreds of micrometers with a precision below 10 μm. The fluorescence method allows the measurement of the wetting rate on the packing sheets' surface excluding perforations and geometry irregularities. These observations highlighted the strong instability of falling water films. The statistical distributions showed a mean water film thickness between 300 and 600 μm. Under industrial operating conditions, the wetting rate is far below 100%, and it increases when the water flow inlet increases; meanwhile, the thickness is not significantly affected for non-total wetting.