Losses in the inlet section of counterflow wet-cooling towers

[摘要] ENGLISH ABSTRACT:The flow resistances in the inlet sections of counterflow wet-cooling towers are investigated andcorrelations are derived for inclusion in a one-dimensional tower performance model.The rain zone loss is modelled using analytical-numerical methods. Experimental verification ofthe model produces satisfactory confirmation of the method's general validity. Semi-empiricalcorrelations are produced to predict the loss coefficient as a function of six dimensionlessvariables for both rectangular and circular cooling towers. In addition, a study is made of the heatand mass transfer in the rain zone and its influence on tower performance.The inlet loss coefficients for dry, isotropically packed, circular and rectangular counterflowcooling towers are determined experimentally and empirical correlations are formulated to fit thisdata. The inlet losses for isotropic-resistance-fill towers are found to be higher than those fororthotropic-resistance-fill towers.Computational fluid dynamics is used to investigate the dependence of the inlet loss coefficient onthe rain zone characteristics. The rain zone loss generally dampens the inlet loss, but this couplingis indirect and necessitates a large amount of dependent variables. The numerical model isvalidated by means of experimental data for dry towers and it is found that the degree of accuracyachieved for circular towers exceeds that for rectangular towers. Consequently, the correlationderived to predict this occurrence for circular towers, can be applied more confidently than itsrectangular counterpart. An example is presented wherein the improved accuracy iQ towerperformance prediction, when applying this correlation, is shown. Additional measures for towerperformance enhancement are also explored.

[发布机构] Stellenbosch University