Common Cooling Tower Problems – Interference, Recirculation and Legioellosis
Interference and Recirculation: A number of cooling towers may have to be used if the hot water load is large. The tower are very often installed at one place in the plant for convenience. Interference and recirculation are two common problems with cooling towers placed in proximity. Some of the moist air leaving a tower may be sucked into another tower installed “downwind” in the vicinity of the former [Figure 1(a)] affecting the performance. This is called “ interference ” . Sometimes a part of the moist air from a tower may be sucked into itself by the “forced-draft fan”. This is “recirculation” [Figure 1(b)]. The ratio of the “plume velocity” to the “wind velocity” is an important factor to determine the extent of recirculation. If this ratio is small, a forced-draft tower becomes more susceptible to recirculation [Figure 1(c)]. Both the phenomena of interference and recirculation reduce the enthalpy driving for cooling and adversely affect the performance of cooling towe...