Mechanical-draft cooling towers

Mechanics-draft cooling towers normally are designed for L/Q ratios ranging from 0.75 to 1.50 accordingly, the vSues of KaV/L vaiy from 0.50 to 2.50. With these ranges in mind, an example of the use of the nomograph will readily explain the effecd of changing variables. 

Lichtenstein, J. "Performance and Selection of Mechanical Draft Cooling Towers, " ASME Trans. (1943). 

Mechanical-draft cooling towers are normally supplied with either central baffles or inlet louvers. This depends on the tower dimensions. On these towers the wind or spray blowout is generally confined to relatively small singlecell units where an inlet may be provided on all four faces. In this case the major remedy is to provide internal diagonal baffles to prevent crossflow of air through the air inlets. 

Mechanical-draft cooling towers can be either field-constructed or factory-assembled systems. Installations that are constructed onsite are generally those employed at utility stations. Factory-assembled towers have applications in smaller industrial operations. 

Figure 4.16 Design elements of mechanical-draft cooling towers.

An inherent problem with mechanical-draft cooling towers is the potential for recirculation. Normally, a high air velocity discharge provided by fans will eliminate this problem. 

These problems are typical in mechanical-draft cooling towers and virtually nonexistent in hyperbolic towers because of the height of vapor discharge. The magnitudes of interference and recirculation depend primarily on wind... 

In places in which ground fog is undesirable, the dry-wet mechanical-draft cooling tower is the best solution. It will have its wet peaking tower out of service during the cooler months of the year, thereby substantially eliminating the fog problem and totally eliminating the icing problems of wet towers. 

Cabral, B. F. A. Winter Operation of Mechanical Draft Cooling Towers, Heat Transfer Survey (1974). 

Performance Curves for Mechanical Draft Cooling Towers Hallett, G. F. 

Under certain conditions, the exhaust air of conventional mechanical draft cooling towers may form a fog plume, causing visibility and icing problems to highways and equipment. In cases where this cannot be tolerated, a combination wet/dry cooling tower is shown to be effective fog plume control method. The paper describes the basic phenomena of cooling tower fog formation. The operation and performance characteristics of the wet/dry tower are discussed as well as a method of select wet/dry design criteria. 11 refs, cited. 

A method is given for predicting the costs of large evaporative type natural and mechanical draft cooling towers as functions of the main design parameters. The costs and parameter factors are expressed analytically for use in power plant optimization programs. 3 refs, cited. 

Mechanical draft cooling towers either force or induce the air which serves as the heat-transfer medium through the tower. For their driving force, natural draft cooling towers depend upon the density difference between the air leaving the tower and the air entering the tower. 

The effects of wet bulb, approach and range on mechanical draft cooling tower size is indicated in Figure 9-118. 

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