Coolers cooling towers

Naphthalene processing, final coolers, and final cooler cooling towers No ( zero ) emission 40 CFR 61.134 EPA 1989a... 

Cooling tower blowdown can be reduced by improving the energy efficiency of processes, thus reducing the thermal load on cooling towers. Alternatively, cooling water systems can be switched to air coolers, which eliminates the problem altogether. 

Other energy considerations for cooling towers include the use of two-speed or variable-speed drives on cooling-tower fans, and proper cooling-water chemistry to prevent fouling in users (see Water, industrial water treatment). Air coolers can be a cost-effective alternative to cooling towers at 50—90°C, just below the level where heat recovery is economical. 

Chilled water Water that is cooler than ambient temperature, obtained from a refrigeration plant, cooling tower, or a well. 

Figure 10-184. Combined system using cooling tower and air-cooler units. (Used by permission Hudson Products Corporation.)...

This cooling water is usually arranged in a closed loop with the water being pumped through secondary coolers or over cooling towers and then returned to the jackets for reuse. Water quality must be good, with steam condensate being preferred, properly treated to prevent corrosion, etc. 

In a water cooling tower, the temperature profiles depend on whether the air is cooler or hotter than the surface of the water. Near the top, hot water makes contact with the exit air which is at a tower temperature, and sensible heat is therefore transferred both from the water to the interface and from the interface to the air. The air in contact with the water is saturated at the interface temperature and humidity therefore falls from the interface to the air. Evaporation followed by mass transfer of water vapour therefore takes place and latent heat is carried away from the interface in the vapour. The sensible heal removed from the water is then equal to the sum of the latent and sensible heats transferred to the air. Temperature and humidity gradients are then as shown in Figure 13.18 . 

Applications include reactor off-gas quenching, vacuum condensers, cooler-condensers, desuperheating and humidification. Water-cooling towers are a particular example of direct-contact heat exchange. In direct-contact cooler-condensers the condensed liquid is frequently used as the coolant, Figure 12.65. 

Alternatively, air-cooled heat exchangers can be installed within the cooling water network to replace cooling water coolers. This has the effect of reducing the cooling load on the cooling tower and, in principle, allows the flowrate of cooling water to be decreased. 

Situations are often encountered when cooling water networks need to increase the heat load of individual coolers, which requires investment in new cooling tower capacity. Such situations demand a more complete analysis of the whole cooling water system. 

With the cooler well water substituted for the warmer cooling-tower water (T2 - T,) has increased by... 

The simplest way to lower the compressor discharge pressure is to reduce the cooling-water temperature to the condenser. One neat trick I have used is to use the cooling-tower makeup water on a once-through basis, to the refrigerant condensers. This supply of water is almost always 10 to 20°F cooler than the cooling-water supply. 

Climatic data. Winter and summer temperature extrema, cooling tower drybulb temperature, air cooler design temperature, strength and direction of prevailing winds, rain and snowfall maxima in 1 hr and in 12 hr, earthquake provision. 

Induction motors are the most frequent in use because of their simple and rugged construction, and simple installation and control. They are constant speed devices available as 3600 (two-pole), 1800, 1200, and 900 rpm (eight-pole). Two speed models with special windings with 2 1 speed ratios are sometimes used with agitators, centrifugal pumps and compressors and fans for air coolers and cooling towers. Capacities up to 20,000 HP are made. With speed... 

The choice of appropriate equipment often is influenced by considerations of price. A lower efficiency or a shorter life may be compensated for by a lower price. Funds may be low at the time of purchase and expected to be more abundant later, or the economic life of the process is expected to be limited. Alternate kinds of equipment for the same service may need to be considered water-cooled exchangers vs. air coolers, concrete cooling towers vs. redwood, filters vs. centrifuges, pneumatic conveyors vs. screw or bucket elevators, and so on. 

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