Cooling Treatment

Power, process, and refrigeration systems all develop a sizable byproduct heat. Whether generated from a centrifugal or reciprocating refrigeration machine or an absorption machine, heat needs to be dissipated. Typically, this is accomplished by recirculating water through a cooling tower. Scale deposition, corrosion, micro biological growth, and fouling can cause problems in the cooling system’s heat exchangers, water-carrying lines, and other system components.

If cooling water is left untreated, a point is reached where the water can no longer maintain the impurities in solution. This is called the level of saturation. The level of saturation depends upon temperature, concentration, and level of pH.

Scale deposits interfere with heat exchangers and reduce their efficiency by insulating the heat transfer surfaces. The most common form of scale in cooling water systems is calcium carbonate (CaC03). In the water, calcium ions combine with bicarbonate to form calcium bicarbonate: (Ca++)+(2HCO) Ca(HCO3)2.

As the temperature of the system increases, calcium bicarbonate is converted to calcium carbonate in the following manner: Ca(HCO3)2+heat> CaC03+H20+CO2.

If scale deposits are left to accumulate, water flow is restricted and piping and heat exchanger tubes become plugged. Ultimately, ignoring scale depositions can lead to the destruction and possible failure of heat exchanger tubes. In addition to loss of efficiency, process contamination can occur.

Cooling systems are continuously infected with microorganisms. If not controlled, micro biological populations multiply rapidly in the warm cooling-water environment. The accumulation of micro biological growths can lead to fouled heat exchangers, metal deterioration through corrosion, and clogged filters and screens.

Fouling results from the physical accumulation of suspended solids on heat exchanger surfaces. Suspended solids include micro biological growths or byproducts, organic material, and precipitated inorganic matter.