Wet cooling systems

These towers combine features of both dry and wet cooling systems. They not only conserve water, but also minimize plume formation. Wet/dry towers are a combination of evaporative and dry cooling. Figure 4.24 shows... 

There are dry cooling systems, in which the heat transferred is dissipated directly into the atmosphere using a dry cooling tower, and wet cooling systems, which use a variety of heat-rejecting devices in their water circuits such as ... 

Wet cooling systems often employ once-though water, drawn from the sea, a lake, or a river. Where adequate supplies of water are available, once-through cooling systems are still one of the primary choices for large users, such as power generation or major industrial processors. 

Biofouling involves the formation of biofilm, whereby hydrated algal- or bacterial-based slimes adhere to water-wetted cooling system surfaces and often contain scales, corrosion products, or other debris embedded within a polysaccharide matrix. The role of biofilms in reducing cooling system efficiency and life span is still imperfectly understood. 

Wet-surface air coolers should not be used where the surface temperature of the exchanger exceeds 150°F (65°C), because scaling will occur.19 The pretreatment of the water is similar to that used in the open-loop cooling systems discussed previously.19 The amount of blowdown necessary depends on the water properties and... 

Fixed water spray systems designed on an area coverage basis may also be used to wet/cool structural steel supports. In this case, the placement of discharge nozzles should be close, usually within 4 ft (1.2 m) of the steelwork being protected. Alternatively additional nozzles or a separate system may be provided. 

CEI produced the Sulphlex-233/ in 7.5 ton (6.8 tonne) batches the reaction vessel has a nominal 9 ton (8.2 tonne) capacity, is steam heated, and is equipped with a wet scrubber system to control potential hydrogen sulfide emissions. Since no cooling capability was available, the reaction exotherm was controlled by the rate at which the preblended chemical modifiers were added to the reaction mass. 

Dry and Wet-Peaking Tower Cooling Systems for Power Plant Application... 

The paper notes that the most economical solution for any design is a combination of conventional wet cooling towers with direct air cooled condensers. Various limitations at particular sites, such as ambient air conditions which require that wet cooling tower plumes be avoided, makeup water quantity available, and maximum turbine backpressure acceptable only dictate the individual design data for the wet and dry sections. The author describes simple methods to determine the design of both individual sections. To meet makeup water and/or backpressure requirements the wet and the dry section must not necessarily be combined into one unit. However, one combined cooling system is required to avoid wet cooling tower plumes. 

A discussion of fan systems used in dry and wet cooling towers covers their general design, system efficiency, system losses due to design of the fan and its housing and to unwanted air movements, and a series of full-scale fan tests which demonstrated the contributions of various components to fan system efficiency. 

Small dry cooling systems are commonplace today all over the world for various light duties, such as localized air conditioning, while larger systems are used in arid areas, often for electricity generation. Dry cooling systems, by their definition, do not need water they are more flexible in their siting requirements than wet systems and are less expensive to maintain. However, they are not as thermally efficient, and therefore are more expensive to own and operate for a comparable heat load. 

The most critical components of a cooling system —the heat exchangers— are seldom available for regular inspection. Therefore the cooling tower usually becomes the primary focus for an inspection of the cooling system, and a subsequent estimation of the degree of cleanliness and condition of internal water-wetted surfaces. Individual tower components and sections need to be regularly inspected and an overall assessment made, with an action plan for improvement if required. 

Typically limit to 2500 to 3500 ppm TDS maximum in the cooling system, depending on circumstances. High levels can increase the tendency for galvanic corrosion. Levels of over 5000 ppm TDS can affect thermal performance and may be detrimental to wood in alternatively wet/dry cooling tower zones, such as the fan deck and louver faces. 

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