Cooling towers basically remove heat from hot water using evaporation. Hot water enters the cooling tower and spray nozzles distribute it over a porous filling material. A fan forces the air to flow through the porous material, causing a portion of the water to evaporate. The evaporation takes heat out from the water. Et voilà!

The problem is that the porous filling material has a complex meshed structure. You don’t want to represent this level of details on an entire tower simulation. The solution is to use the Darcy-Forchheimer law to characterize the pressure drop caused by the porous material:

Where S is a source term added to the Navier-Stokes equations. This term is composed of a viscous loss term and an inertial loss term, creating a pressure drop that is proportional to the velocity and velocity squared, respectively.

On this particular project, the simulation helped the client improving his product on several aspects:

• Pressure distribution on the head section to reduce pressure loss and noise (different shapes have been tested)
• Test different porous filling material to see the effect on the global pressure loss of the system
• Detect flow separation
• Test the impact of louvers on the outlet

Streamlines in the cooling tower