Simultaneous sub-dew point cooling and deep dehumidification by Combined Sorption Dehumidification and Evaporative Cooling (CoSDEC) at low regeneration temperature

Decoupled desiccant dehumidification and evaporative cooling technologies can efficiently dehumidify and cool air using predominantly low-grade heat and water. However, as the target temperature and humidity decrease, the temperature required for desiccant regeneration increases, which in turn decreases sorption capacity. In this study, we introduce the concept of Combined Sorption Dehumidification and Evaporative Cooling (CoSDEC) wherein air is simultaneously dehumidified via sorption and cooled via evaporative cooling in a pair of adjacent desiccant-coated and water-wet channels. A 900-mm proof-of-concept system employing mesoporous silica gel desiccant regenerated at 40 °C is demonstrated to dehumidify and cool 1.0 m/s of hot and humid air from 30 °C and 20 g/kg da to a minimum of 15.6 °C and 4.8 g/kg da. This yields a cooling effectiveness of εwb = 3.76 and εdp = 2.85, and a dehumidification effectiveness of MREadb = 5.2 and MREiso = 1.75. Further enhancements were achieved by decreasing flow velocity (15.4 °C and 4.6 g/kg da at 0.8 m/s), increasing regeneration temperature (15.3 °C and 2.8 g/kg da at 50 °C), or increasing system length (13.9 °C and 4.2 g/kg da at 1200 mm). The remarkable capability of CoSDEC to efficiently dehumidify and cool air to substantially low humidity and temperatures using a low-temperature heat source and water represents a significant achievement in heat-driven air conditioning technology. The potential for further reduction in temperature and humidity levels through the optimization of operational and design parameters underscores the promise of a combined sorption dehumidification and evaporative cooling system.