Wood, for a long time, was the most commonly used filling material in cooling towers. A very old method.
For hundreds of years, bundles of woods have been used and arranged randomly inside the tower. The system has evolved when wood plates were introduced and arranged in an orderly manner. But the use of wood brought many problems, such as lack of resistance and other problems related to chemical treatment for making them last longer.
In Europe, it was difficult to find suitable wood. America had an advantage because wood plates filling material was easier to find and to use for the scope of cooling towers. Moreover, it could be bought at a lower cost compared to the European market.
So, for over thirty years, the whole cooling tower industry had tried to find viable alternatives to wood. First alternative was fill material made of paper (hot polymerized cellulose sheets soaked with phenolic resins). The main advantage of using this material was changing from splash system to film system on paper support. But, even this method brought many disadvantages: the fragility of paper limited its use and, moreover, once the channel between the sheets became clogged, it could no longer be cleaned. Hence, all material needed to be completely replaced.
From sheets of paper to plastic, achieving considerable success. The plastic sheets, inert and easily modeled, in the long run, have also presented some weaknesses in the evaporation process. Clogging presented one weakness during water passage and, even worse, air passage.
Assembly of these plastic sheets mono-blocks is generally carried out at the time of manufacturing and, hence, are huge in size. This has an impact on the final cost due to their transportation.
