Cooling Tower Fill: Film, Splash and When Each One Wins

Fill exists to hold water in contact with air for as long as possible across as much surface as possible. Everything else in the tower serves that exchange: the fan supplies the air, the distribution spreads the water, the fill is where the heat actually leaves.

That is why fill selection and fill condition dominate thermal performance. A tower with the right fan, the right pump and degraded fill will not make its approach.

Film fill is made from thin corrugated PVC sheets bonded into blocks. Water spreads across the sheets as a thin film, which creates an enormous surface area inside a small volume. For clean water it is the most efficient option by a wide margin, and it is what we fit as standard.

The efficiency comes from narrow passages, and that is also its weakness. Standard film fill uses 19 mm flutes, and anything in the water that can bridge a 19 mm gap will eventually block it: silt, biological growth, process oils, fibres.

Once flutes block, air stops passing through that part of the pack. The tower loses capacity in the places that are still nominally wetted, which is why a fouled film fill tower can look perfectly normal from outside while missing its duty by several degrees.

Splash fill takes the opposite approach. Instead of spreading water into a film, it repeatedly breaks the falling stream into droplets against staggered bars or grids. Surface area comes from the droplets rather than from a wetted sheet.

It is markedly less efficient per cubic metre, so a splash fill tower is taller or larger for the same duty. In exchange, there is nothing narrow to block. Water carrying silt, fibres or biological load passes through and keeps passing through.

For steel plants, foundries, paper mills and any circuit with genuinely dirty water, splash fill is often the only sensible answer, and the extra height is simply the price of a tower that keeps working.

Between the two sits low fouling film fill: wider flutes, typically 27 mm or more, with a simpler corrugation that gives debris fewer places to lodge. It gives up some efficiency against standard film fill and buys a great deal of tolerance.

This is usually the right answer for moderately dirty circuits, cooling towers exposed to dusty sites, and anywhere the water quality is uncertain. It also suits plants that cannot easily take a cell off line for cleaning.

The choice is a judgement about your water rather than a preference. Send us an analysis, or describe what the circuit has been doing to its existing fill, and the answer is usually obvious.

Fill is a consumable. On reasonably clean water it lasts five to eight years; on dirty water considerably less. The failure is gradual, so it needs to be looked for rather than waited for.

Most towers that no longer hold their approach do not need replacing. They need the fill pack renewed, the nozzles cleared and the drift eliminators refitted. That work typically restores rated duty for a small fraction of the cost of a new unit.

We supply fill cut to existing pack dimensions for towers of any make, and can fit it during a planned shutdown. If you are being quoted a new tower for a performance problem, it is worth having the fill inspected before you sign.