Preparation and Application of UiO-66 in Desiccant-Coated Heat Exchanger-Based Desiccant Cooling Systems

Abstract

Dehumidification performance of a high-efficient compact desiccant cooling component named desiccant-coated heat exchanger (DCHE) highly depends on coated desiccant materials. Currently, mesoporous silica gels and salt-supported silica gels have been extensively studied. Silica gels have limited adsorption quantity in the middle relative pressure range, while salt-supported silica gels have potential threat of corrosion. In this work, a metal–organic framework UiO-66 that can achieve good adsorption quantity without corrosion is reported. The equilibrium adsorption test shows that UiO-66 has promising water uptake, especially in the relative pressure range of 0.35–0.65. The adsorption kinetics test displays that UiO-66 exhibits desirable dynamic water uptakes and adsorption rate constant. Dehumidification capacities of a DCHE using UiO-66 are estimated via a mathematical model and compared with silica gel- (SG) and LiCl-supported silica gel (SG/LiCl). Simulation results show that UiO-66 has better dehumidification performance than both SG- and SG/LiCl-coated samples for semiarid and semihumid climates when outdoor temperature is lower than 36 °C. Especially, when the temperature and relative pressure of inlet air are set as 30 °C and 0.35, respectively, its dehumidification capacity can be 2.7 times the amount of the SG-coated one and 1.3 times of the SG/LiCl-coated one. However, it should be more prudent in choosing UiO-66 under hot and humid climates.

Water adsorption performance of UiO-66 modified by MgCl2 for heat transformation applications

“…[11,20] In most of AHT applications, porous materials needed superior water adsorption performances within a relative humidity range of 0.05 < P/P 0 < 0.32. [21] However, the water adsorption capacity of UiO-66 reached just 0.1 g/g-0.2 g/g at P/P 0 = 0.3, [11,22] which should be improved. The UiO-66 was modified mainly by introducing functional groups [11,23] and metal ions [24][25][26] to enhance its adsorption performance.…”

Suitability of bio-desiccants for energy wheels in HVAC applications

“…Various studies have reported the utility of silica gel [23,24] zeolites [12,25] metal-organic frameworks [26,27] and activated alumina [28,29] as desiccant coatings in heat exchangers or wheels. The main differences between desiccant coated exchangers (DCHE or desiccant wheels) from conventional energy wheels is need for a dedicated section for regeneration for DCHE, which typically requires a heat source.…”