In today's world of expensive energy, it is more vital than ever for heat exchange equipment to be kept free of insulating deposits that promote high energy consumption. The four principal sources of these deposits in the case of water cooled systems are: scale, corrosion, biological growths and sludge. These factors are important for another reason: they have a direct effect on equipment life.
SCALE
Caused by the precipitation of calcium and other salts of limited solubility, scale, in addition to its high insulating value, progressively narrows pipe internal diameters and roughens tube surfaces, thereby impeding proper flow.
In compression refrigeration systems, scale translates into higher head pressures, hence an increase in power requirements and costs. For example, 1/8" of scale in a 100 ton refrigeration unit represents an increase of 22% in electrical energy compared to the same size unit free of scale. Similarly, in absorption systems, scale creates a higher back pressure on the concentrator, increasing energy expenditure.
While scale formation proceeds more rapidly in open recirculating systems owing to the concentration effect of evaporation, once-through systems are not exempt from scaling if high temperatures are combined with silt and iron.
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