It’s Time to Rethink Cooling Tower Filtration

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Courtesy of Amiad Filtration Systems Ltd.

ABSTRACT
The dissipation of ambient or process heat in large HVAC systems, manufacturing facilities, power generation plants, refineries, metal mills and forges, chemical plants and food processors is most often accomplished by cooling towers. These simple structures facilitate the transfer of unwanted energy (heat) from a transport liquid (usually water) to the atmosphere. The bane of cooling towers, with relation to efficient heat transfer and pathological risks to employees, is
suspended solids. These solids can originate in the process, in the piping, from the atmosphere or from internal biological growth. Side-stream filtration is the most commonly used method of maintaining minimal suspended solids in the cooling system. Present-day systems rely mainly on two established methods of suspended solids removal. The first utilizes cyclonic principles that are highly efficient at removing high specific gravity solids. The other method is granular
media filtration that is generally efficient at removing low specific gravity organic solids. Automatic self-cleaning screen filter technology not only removes both organic and inorganic solids regardless of specific gravity but also requires very little energy to operate and conserves coolant additives by using very little coolant liquid for the self-cleaning process. By incorporating the cleaning cycle into the blow-down process of the cooling tower system, the unwanted loss of any coolant can be completely eliminated.

INTRODUCTION
Open cooling systems are composed of a cooling tower, a basin, pumps and a heat source. A cooling tower is an enclosed devise using air to cool water by evaporation; thus, the atmosphere becomes the heat sink. Cooling towers are generally of two basic types: natural draft and mechanical draft. The former depends upon natural atmospheric conditions to move air through the tower while the latter uses mechanical fans to move air through the tower. Mechanical draft can be either forced-draft design where air is pushed through the tower by fans located near the
incoming air or induced-draft type where air is pull through the tower by fans placed in the air exiting the tower. The basin is generally located beneath the cooling tower to catch and contain the cooled water, accommodate liquid expansion and contraction, serve as a reservoir for the storage of surplus water, and act as the sump for the cooling system pumps. The pumps move heat through the system by circulating cooled water to the heat source where heat is absorbed. Flow continues, moving the heated water back to the cooling tower where the heat is transferred to the atmosphere. The heat source is where the water picks up the unwanted energy in the form of heat.

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