What is the definition or description of fouling factor in chiller?

Answer 1

Impurities in the chilled water system eventually deposit on evaporator tube surfaces, impeding heat transfer. Cataloged performance data includes a "fouling factor" that accounts forthis effect to more closely predict actual chiller performance. Research conducted by theAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)reveals that the negative effect of fouling on the long-term performance of closed-loop chilled water systems is usually less than 0.00025 h·ft²·F/Btu. ARI Standard 550/ 590-1998 reduces the fouling-factor allowance from that value to the 0.00010h·ft²·F/Btu suggested by the study results.

Its Effect... Assessing a smaller fouling factor lets specifying engineers, owners, and manufacturers alike take credit for seemingly better heat transfer. With cataloged performance that more closely matches actual operation, specifying engineers can select chillers with greater precision-and owners purchase no more cooling capacity than they actually need. [The revised evaporator fouling factor has little effect on full-load efficiency, i.e. roughly 2 percent. As noted later,full-load efficiency remains an important criterion in many applications.-Editor]