Cooling tower spray filled

Figure 9-104. Spray-filled counterflow induced draft cooling tower. Used by permission of The Marley Cooling Tower, a United Dominion Co.

The key properties of mixtures of air and water vapor are described in Section 9.1. Here the interactions of air and water in packed towers under steady flow conditions will be analyzed. The primary objectives of such operations may be to humidify or dehumidify the ait as needed for particular drying processes or other processes, or to cool process water used for heat transfer elsewhere in the plant. Humidification-dehumidification usually is accomplished in spray towers, whereas cooling towers almost invariably are filled with seme type of packing of open structure to improve contacting but with minimum pressure drop of air. 

Cooling towers are classified according to the method by which air is introduced to the tower. The principal types are atmospheric spray, natural-draft, mechanical-draft, deck-filled, spray-filled, coil shed and hyperbolic towers. Most industrial cooling tower installations are field-erected units designed for specific thermal characteristics. 

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. 

Rgure 9-102. Cross-section of low-head forced-draft tower showing fan housing arrangement, filling, water distribution spray system and spray eliminators. Used by pennission of Foster Wheeler Corp., Cooling Tower Dept. 

Sprays and droplet streams were frozen by injection into an atmosphere of cold, stagnant air in a stainless steel tube (length 112.5 cm, diameter 15 cm) with an LN2-filled cooling jacket (Fig. 10.2). The droplets were injected into the top of the freezing tower at room temperature and were frozen in cold air at temperatures between 90 and 180 °C in the lower parts of the tower. A gas permeable exhaust segment cormected the freezing tower with the LN2-cooled collecting vessel. The temperature was monitored at the nozzle position, the upper and lower tower position and the vessel [8]. 

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