Experimental investigation for a non-adiabatic desiccant wheel with a concentric structure at low regeneration temperatures

The desiccant wheel-based air-conditioning system has been considered to be an effective alternative to conventional air-conditioning systems to reduce energy consumption in buildings. However, the adsorption and carryover heat released during the wheel's working process both significantly restrict dehumidification and energy performance. Moreover, it is also difficult to apply a low temperature of thermal energy, including solar thermal energy and waste heat, in the desiccant wheel-based air-conditioning system. To improve the dehumidification and energy performance, and use a low temperature of thermal energy, this study designed, constructed and tested a non-adiabatic solid desiccant wheel, which is based on a concentric ring design. The wheel's structure was fabricated from Nylon, using three-dimensional technology with polymer desiccant materials inserted into the channels between each of two rings. Then, cooling water was brought into the narrow passages inside the rings on the process air side of the wheel, with the aim of transforming the dehumidification process from quasi-adiabatic to quasi-isothermal. A series of experiments were then conducted to investigate this system's performance under various operating conditions. The measurements showed that, when the inlet air and cooling water temperatures were 25 degrees C and 24 degrees C, respectively, the dehumidification performance of the new wheel was approximately the same as that of a conventional desiccant wheel. However, when the inlet temperature of the process air was 35 degrees C, the dehumidification process of the new wheel was very close to the ideal for a desiccant wheel - an isothermal dehumidification process. In this condition, the enthalpy effectiveness of the tested wheel was also 11% higher than that of a conventional wheel.