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.

The invention of air-conditioning in the early 20th century and its development since then has brought many advantages to mankind. In spite of this many people are not very satisfied with the indoor environment at their workplace. They complain about the air quality, the cold draught they experience, fan noise and dry air, causing dry eyes and throats, notorious elements of the so-called Sick Building Syndrome. As an experienced HVAC designer I asked myself if we could do better. Looking at termite hills, where termites closely work together, build their dwellings with natural air-conditioning but high Indoor Environmental Quality, a doctoral research was started. This implies a building designed as a "climate machine", activated by gravity and the ambient energy of the earth mass, the wind, and the sun, metaphorically referred to as Earth, Wind & Fire. After 5 years of modelling, simulating, testing and validating it was demonstrated that natural air-conditioning in buildings is feasible. An air-conditioning without fans, nevertheless able to maintain an excellent indoor climate. This paradigm shift in air-conditioning not only promises an excellent Indoor Environmental Quality, but also an improved relationship of architect and engineer and much lower energy use of buildings.