CFD study for downdraft cooling in large buildings

Natural air conditioning with the Earth, Wind & Fire concept presents opportunities for office buildings. The core of the climate system is the Climate Cascade© which is designed as an architectural shaft and performs as a gravity-activated heat exchanger for conditioning the ventilation air. Ventilation air is being cooled or heated, dried or humidified as needed, by means of sprayed water droplets at the top of the shaft by full cone spray nozzles. The droplet size distribution applied here is not fine, as no cooling due to evaporation like for adiabatic cooling is required; instead the heat exchange is due to the inert heating of large amounts of cool, quite coarse water droplets of approximately 13 °C in summer and winter conditions. By momentum transfer from droplets to air, the downward air movement from the over pressure room is enhanced. This aerodynamic pressure, together with the hydraulic pressure and the downward thermal draft, reduces the need for fans. After successful testing in small scale the concept will be installed in a new hotel building in Amsterdam. This CFD study will explain the effect of the evaporation and condensation of a cool droplet spray computed with the Lagrangian discrete phase model. The model considered both evaporation and condensation at the same location and the computed temperature and relative humidity showed good agreement with the measured test results.