Performance characteristics of a trickle fill in cross- and counter-flow configuration in a wet-cooling tower

In cooling towers packed with trickle or splash fills, which have almost isotropic or anisotropic flow resistance, the air flow through the fill is oblique or in cross-counterflow to the water flow, particularly at the cooling tower inlet when the fill loss coefficient is small or when the fill hangs down into the air inlet region. This results that the fill Merkel number or transfer characteristic for cross-counterflow is between that of purely counter- and cross-flow fills.When using CFD to model natural draught wet-cooling tower performance for isotropic or anisotropic fill resistance, two- or three-dimensional models and fill characteristics are therefore required to determine overall fill performance.In this paper, the test facility, measurement techniques and methods of analysis used to determine fill performance characteristics in counter- and cross-flow configuration are presented and discussed. Results obtained for a specific fill are presented and discussed which can be used for the evaluation of cross-counterflow fill performance.

► Fill tests are performed on a trickle fill to accurately determine anisotropic fill behavior. ► Fill performance is found to have a strong dependency on fill configuration. ► High ratios of Gw/Ga favor crossflow, while low ratios favor counterflow. ► In counterflow trickle fill behaves similar to film fill. ► From test results, conclusions about heat transfer and fluid mechanics in the fill are made.