Numerical and Experimental Analysis of an Evaporation Cooler

Evaporation coolers are commonly used to cool hot off-gases by injecting water droplets, which vaporize and thus cool the off-gas so that it can be filtered in the next process step. In this paper the flow and heat and mass transfer in a full scale industrial evaporation cooler are predicted with CFD methods. Three different configurations are compared and evaluated with respect to the flow homogeneity at the spray nozzle plane. In addition, the cold air flow without droplet evaporation in a lab scale model is investigated with CFD as well as PIV (particle image velocimetry) measurements and comparisons are given. In the CFD simulation model all phases involved (off-gas, water droplets, water vapor and dust) are considered. Water droplets and the dust phase are modelled by an Euler/Lagrangian dispersed phase model which allows for a phase change from water droplets to vapor. The mass fraction of water vapor is computed by a diffusion/convection equation. The equations of the Eulerian and Lagrangian phases are fully coupled (the influence of the dispersed phases on the continuous phases and the phase change from water droplets to vapor is realized by appropriate source terms in the Eulerian phase equations). Turbulent particle dispersion is modelled by a stochastic tracking technique.