Performance monitoring of closed cooling towers for fouling detection.

Fouling is a permanent problem in process technology and is estimated to cost 0.25% of the gross national product. Evaporative cooling systems, which are often used in refrigeration systems to dissipate condenser heat to the environment, are also susceptible to fouling: as they work with untreated outside air, they are exposed to both natural (e.g. pollen) and human-made (e.g. industrial dust) contaminants. Also suspended solid particles and dissolved salts in the spray water are an issue. Since hardly any congruent data on the quantitative influence of fouling on the thermal performance of cooling towers (CT) are available, Fraunhofer ISE conducted a corresponding series of tests. For this purpose, a closed CT was tested under a variety of operating conditions and with different calcification conditions of the tube bundle. For the evaluation of the results, a graphical and a model-based method were compared, of which the latter turned out to be more suitable. With an average scaling thickness of around 1mm on the tube bundle, the reduction in performance is approx. 15%.