![]() ![]() ![]() A comprehensive comparison between the Merkel, effectiveness-NTU and Poppe methods is presented in Kloppers and Kröger, which concluded that the Poppe method, being the most algebraically-involved, is also the most accurate for the design of hybrid wet/dry cooling towers. Modeling the heat and mass transfer in a wet cooling tower, particularly within the fill zone, has been performed since the seminal work of Merkel, followed by the effectiveness-NTU method, Poppe method and Klimanek method. On the other hand, visible plumes, water conservation and drift deposition are closely related to the environmental impact, as is plume rise, which dictates the maximum ground concentration of air pollutants. For instance, a reduction in the fan power consumption or pump head facilitates a more efficient operation. As defined by Holiday and Alsayed, sustainability in a cooling system encompasses efficient operation, impact on the environment, depletion of natural resources and ecology. 1 and 2, wet cooling towers are classified as counterflow and crossflow according to the respective directions of the air and water streams. In general, two types of cooling towers, i.e. wet and dry, are used these exploit evaporative and non-evaporative heat transfer mechanisms, respectively. Problems of particular interests are plume rise/deflection, condensation and drift deposition, the latter consideration being a concern of public health due to the possible transport and spread of Legionella bacteria.Ĭooling towers are heat dissipation devices commonly found in industrial plants and HVAC systems. To this end, numerous attempts, being either theoretical or numerical or experimental, have been proposed to predict plume behavior in atmospheres that are either uniform versus density-stratified or still versus windy (whether highly-turbulent or not). Of course, no assessment of the severity of a visible plume can be made without first understanding its atmospheric trajectory. In this review, we contrast established versus novel technologies and give a perspective on the relative merits and demerits of each. Recently, passive technologies, which make use of free solar energy or the latent heat of the hot, moist air rising through the cooling tower fill, have been proposed to minimize or abate the visible plume and/or conserve water. The parallel path wet/dry cooling tower is one of the most commonly used approaches for plume abatement, however, the associated capital cost is usually high due to the addition of the dry coils. Visible plumes above wet cooling towers are of great concern due to the associated aesthetic and environmental impacts. ![]()
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