NSTI Nanotech 2009

Water Conservation in Cooling Towers Using Controlled Hydrodynamic Cavitation

P. Vella
VRTX Technologies, US

Keywords: cavitation, cooling tower, water conservation, LEED

Abstract:

Cooling towers are a component of some buildings’ cooling systems. Where installed, cooling towers can account for up to 30% of the total water used in an average building, a statistic that can be even higher during summer months. Water is lost in cooling towers by evaporation (which provides cooling), bleed (to prevent build-up of dissolved and suspended solids), drift (water droplets entrained in exhaust air), splashes, overflow, and leaks. Cooling tower systems are very dynamic, and treatment of the water is required to control microbial growth, scaling, corrosion and fouling. Due to more stringent environmental regulations and the escalating cost of water, a need is felt in industry to improve the performance of open recirculating cooling water systems, and to minimize the impact on the environment (surface water) of the discharge of cooling water containing chemical treatment additives as well as to economize on energy. The paper describes an alternative, patented non-chemical cooling water treatment system. The system includes a mechanical unit and a separation/filtration unit. The unit works primarily on the principals of Controlled Hydrodynamic Cavitation (CHC). As the cooling water is pumped through the unit, the CHC action destroys microbial cell walls and converts dissolved calcium and bicarbonate ions into calcium carbonate (CaCO3) solids that are separated from the recirculating water by the separation/filtration unit. Case studies are highlighted in the paper to summarize the application of this new treatment system for cooling water applications. Performance data, such as scale control, corrosion and bacteria (Legionella) reduction, are presented. In addition, a 60% – 80% reduction in blowdown and a 20% – 30% reduction in makeup water usage can be achieved. These results indicate that unlike other non-chemical treatment methods, the CHC system offers a complete solution for water related problems that typically occur in circulating cooling water systems. This technology can also provide USGBC LEED credit for new construction (NC) and innovation and design (ID). An additional point may be earned (Water Efficiency 1.2) by utilizing cooling tower blowdown for landscape irrigation purposes.
 
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