In order to propose an alternative to traditional desiccant cooling systems, using desiccant wheel, the CEA — INES, in collaboration with the CNAM-IFFI, developed a multifunctional exchanger (Figure 1a) able to couple heat and mass transfers of the desiccation.

The process air enters the heat exchanger by the centre and then flows in a radial direction between the desiccant bed and the periphery where the air is collected. To heat or cool the desiccant during regeneration or adsorption mode, a copper heat exchanger made of 30 tubes of 10 mm diameter with fins is immersed in the desiccant bed. The exchanger is filled with 50 kg of Engelhard KC — Trockenperlen-N type silica gel. The particles are of spherical shape with a mean diameter of 3.4

mm. The total mass of the prototype is 60 kg. The Figure 1b presents the scheme of a solar desiccant cooling installation using desiccant heat exchangers. The traditional two wheels (desiccant and heat recovery) are replaced by two desiccant exchangers (air and desiccant/water) functioning heated or cooled; the cooling corresponds to the drying step while heating is used for the regeneration. During the regeneration phase, hot water, flowing directly from solar collectors, is used. During the adsorption phase, cold water circulation, resulting for example from a cooling tower or geothermal sinks, maintains the adsorbent under optimal sorption conditions. The prototype of heat exchanger filled with adsorbent was tested and it appeared that the system is able to cool air from 33°C and 40% HR (outside air) to 24°C and 90% HR (blowing air) [1]. A TRNSYS numerical model of desiccant heat exchanger was also developed to simulate the heat and mass transfer for the adsorption and regeneration processes in the prototype. The results of the numerical model are in agreement with the experimental results [2], and systems performances could be evaluate.