Investigation of performance enhancing devices for the rain zones of wet-cooling towers

[摘要] ENGLISH ABSTRACT: The performance of a natural draught wet-cooling tower can be improved by reducing theaverage drop size in the rain zone. In this thesis, the effect of installing different horizontalgrids below the fill on drop size in the rain zone is investigated experimentally andtheoretically. A specially designed horizontal grid consisting of evenly spaced slats and a gridmade from expanded metal sheeting are tested. Drop size distribution measurements are takenbelow different cooling tower fills to determine the respective Sauter mean drop sizes and alsobelow different configurations of splash grids to determine the reduction in drop size. Dropbreak-up through a grid of horizontally placed slats is modelled and compared to measureddata to determine the optimum configuration in terms of spacing between the grid and fill, slatwidth and slat spacing. A cross flow rain zone is modelled under different air and water flowcombinations with CFD for two distributions that represent the rain with and without splashgrids and the results are compared. The Merkel transfer characteristic for all the flowconditions using both distributions are determined using a Lagrangian, Merkel, Poppe and e-NTU method in order to quantify the increase in rain zone Merkel number. Pressure drop overthe cross flow rain zone is also determined and compared for the two distributions underconsiderations.

[发布机构] Stellenbosch University