A critical evaluation and refinement of the performance prediction of wet-cooling towers

[摘要] The thermal performance prediction of wet-cooling towers is critically analyzed and refined. Natural draftcounterflow towers and mechanical draft counterflow and crossflow towers are considered. The Merkel,Poppe and e-NTU heat and mass transfer methods of analysis are derived from first principles, as thesemethods form the cornerstone of wet-cooling tower performance evaluation. The critical differencesbetween these methods, when applied to fill performance analyses and cooling tower performanceevaluations, are highlighted. The reasons for these differences are discussed with the aid of psychrometriccharts. A new extended empirical relation for the loss coefficient of fills is proposed where the viscousand form drag effects are accounted for as well as the buoyancy, momentum and fill height effects. Theempirical equation for the transfer characteristic of fills is extended to include the effects of fill height andthe inlet water temperature. Empirical equations to predict the temperature inversion profile, height of thetemperature inversion and the height from which air is drawn into the cooling tower are developed. Theinfluence of temperature and humidity inversions on the performance of wet-cooling towers issubsequently investigated. A comprehensive analytical computer program is developed to predict andoptimize the performance of wet-cooling towers. Computer programs are also developed to generatecooling tower performance curves, analyze fill performance test data and plot psychrometric charts.

[发布机构] Stellenbosch University