For the demonstration building in Cádiz, an evaporative system has been designed to be installed on the roof. A series of partitions have been positioned above the traditional roof slab to create air channels, closed on its upper face by an insulating material (see Fig 2).
The technology developed in the ReCO2ST project is based on the ability to remove heat from the upper building floor due to the evaporative effect. With this objective, the complete design consists of:
The design procedure has several stages, using CFD method to study the air movement through the air channels and the design of the different layers of the roof composition.
Figure 1 shows a schematic drawing of the partitions’ position represented in red. The position of each partition, its length, and the separation between them has been optimized to reduce pressure drops and ensure a constant air velocity.
The 3 main elements of the construction detail (see figure 2) are from bottom to top: concrete slab, air channel and insulation material. It is very important that insulation is placed above the air channels so that cold air touches the surface of the concrete slab directly to extract heat. The insulation layer above the air channels prevents this air from heating in summer, and from cooling in winter.
The equipment takes air from the atmosphere; according to the thermodynamic cycle for which it is designed, (Maisotsenko cycle), experiences indirect cooling to a temperature that is between the wet-bulb temperature and the dew point without humidity increase. The cooled air is supplied through ducts to the roof, circulating between the air channels of the roof. By circulating between the roof channels, the air removes heat from the roof slab. Finally, the air is exhausted to the atmosphere.
Experiments show that this technology can decrease the temperature of the adjacent space on average up to 4°C, can decrease on average, reducing or even eliminating the need for air conditioning.
Fig 1. Schematic drawing of the position of the partitions.
Fig 2. Construction detail drawing.