Film fill increases heat rejection and reduces air resistance but also adds to the cost of cooling tower construction. Mechanically
assembled film fill offers the same benefits with less labor costs while providing environmental benefits.
Cooling tower film fills first were made of corrugated asbestos sheets or other materials. As engineers saw the benefit of increasing the density (number of sheets per lineal space) of the film fill packs -- from a sheet spacing of 3.94" (100 mm) to 0.75" (19 mm) or less -- other construction materials were considered. Increasing sheet density and having an engineered sheet design improve the cooling potential. The increase in sheet density was allowed by using plastics. Today, the most commonly used film fill sheet material is rigid PVC (Cooling Technology Institute Std. 136). It is durable, provides a long service life, is excellent for wetting (conditioned to allow surfaces to be covered completely by water), is self-extinguishing and can be formed into many shapes (figure 1).