Fan-assisted hyperbolic tower

Recent hyperbolic tower designs have included fans for intermittent operation. This type tower combines the features of both natural-draft and mechanical-draft towers. These resemble natural-draft systems in that they employ a hyperbolic shell however, they are smaller and have large 

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. 

A rule of thumb for the dimensions of fan-assisted hyperbolic towers is as follows  

It should be clear that major differences exist between mechanical- and natural-draft systems. Table 4.1 summarizes our discussion by comparing the two types of towers. 

---

Hyperbolic fan assisted towers may have as much as three times the capacity of the same sized natural draft towers in Figure 9.17(c). They provide greater control than the natural draft systems and may be turned on only at peak loads. A rule of thumb that Cheremisinoff and Cheremisinoff (1981) suggest for the relative sizing is that the fan assisted tower may be 2/3 the diameter and V2 the height of the natural draft towers. 

Figure 9.18. Main types of cooling towers, (a) Atmospheric, dependent on wind velocity, (b) Hyperbolic stack natural draft, (c) Hyperbolic assisted with forced draft fans, (d) Counterflow-induced draft, (e) Crossflow-induced draft, (f) Forced draft, (g) Induced draft with surface precooler for very hot water also called wet/dry tower, [(fc)-(e) from Cheremisinoff and Cheremisinoff, 1981).

In an atmospheric spray tower the air movement - is dependent on atmospheric conditions and the aspirating effect of the spray nozzles. Natural-draft cooling tower operation depends on a chimney or stack to induce air movement. Mechanical-draft cboling towers utilize fans to move ambient air through the tower. Deck-filled towers contain tiers of splash bars or decks to assist in the breakup of water drops to increase the total water surface and subsequently the evaporation rate. Spray-filled towers depend only on spray nozzles for water breakup. Coil shed towers are comprised of a combination structure of a cooling tower installed on top of a substructure that contains atmospheric section coils. Hyperbolic natural-draft cooling towers are typically large-capacity systems. 

---