Crossflow mechanical draft towers

Crossflow mechanical draft towers are thermally less efficient. They offer less resistance to air flow and can operate at higher velocities than counterflow towers, which means less horsepower and smaller cell sizes for comparable outputs. In practice, however, both crossflcw and counterflow designs have advantages and limitations, depending on the type of application. 

On larger multi-celled mechanical-draft towers of both counterflow and crossflow variety, the air inlets are confined to the two opposing faces and windage or drift loss is unlikely to occur, except under exceptionally high wind conditions. Here again, remedial work, depending upon the location, can be applied but at additional cost (see Figure 34.10). 

Mechanical-draft towers have a positive control of air dehvery through the fill by the use of large-diameter fans. Therefore, they can be designed for close control of cold-water temperature. Counterflow and crossflow designs are indicated in Figs. 3.17 and 3.18. 

Cooling towers are broadly classified on the basis of the type of draft natural draft (natural convection), mechanical draft (forced convection) and mechanical and natural. Further distinction is made based on (1) the type of flow i.e. - crossflow, counterflow, cocurrent flow (2) the type of heat dissipation-wet (evaporative cooling), dry, wet-dry and (3) the type of application-industrial or power plant. Each of the major types of cooling towers has a distinct configuration. The major designs are summarized in Figures 1 through 8 and a brief description of each follows. 

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. 

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