Due to increasing environmental requirements and changed loads evaporative coolers are often operated far from the original design. This often results in inefficient operation, wet floors and walls and / or massive caking that can affect the overall structural analysis. With flow simulation of the complete process, optimisation potential can be discovered and the right measure initiated. All the physical effects are simulated, these include, the inflow of the hot flue gas, the injection of the spray, the evaporative cooling, and the outflow of the cold, moist flue gas. The main results obtained are the pressure loss of the entire cooler as well as the trajectories of the spray. Only when the spray evaporates, without wall contact, before the next deflection on a trajectory parallel to the tower axis, is a safe and efficient operation possible. Generally, the inflow of the hot flue gas must be rectified by fittings such as guide and perforated plates immediately before the injection. In addition, the verification and, if necessary, the adjustment of the spray system from the control path to the nozzle tip is mandatory. Lechler is the right contact for the holistic optimisation of such evaporative coolers.