Cooperation of Thermoresponsive Fast-Kinetic Desiccants and Biomimetic High-Flux Heat Exchangers for Low-Temperature Desiccant Coated Heat Exchanger

Description

The beginning of the 21st century has witnessed extreme heat events negatively impacting human society’s treasures, environments and health. These extreme heat events are strongly correlated with the boost in the atmospheric humidity, which not only decreases human body’s thermal comfort and causes severe heat stress, but also degrades indoor air quality and causes hygiene issues. Hence, dehumidification with high efficiency and low carbon emission is crucial for comfortable, healthy, and sustainable livings. Among various dehumidification technologies, desiccant-coated heat exchanger (DCHE) stands out due to its decoupling of sensible and latent loads, effective removal of the exothermic heat of sorption and improved heat transfer effectiveness. However, three major challenges need addressing: (1) improving desiccants’ adsorption capacity for higher water uptake and sorption kinetics for lower shorter period, (2) decreasing desiccants’ regeneration temperature for lower energy input, and (3) improving mass exchange effectiveness with lower pumping power for higher energy efficiency. Therefore, a novel DCHE is desired to be equipped with high adsorption capacities and kinetics, low regeneration temperature, high heat/mass transfer efficiency, and low pumping power. To achieve these goals, we will synergistically integrate a thermoresponsive composite desiccant (TCD) with biomimetic high-flux heat exchangers (HEXs) towards high-adsorption and low-temperature DCHEs, which has yet been reported. The synergy is realized through: (1) TCD, composed of thermoresponsive polymer network and hygroscopic salts, will exhibit fast-kinetic and high-capacity water adsorption due to fast water diffusion and large water-storage volumes, and release water automatically owing to desiccant hydrophilic-to-hydrophobic transition and thus enable low regeneration temperature and low energy input. (2) Biomimetic triply periodic minimal surface (TPMS) HEX will provide high desiccant-moisture heat/mass transfer areas and capacities and low pumping power due to its intrinsic intertwining while smooth flow channels. Detailly, we will firstly build a desiccant sorption-desorption kinetic model and perform adsorption-desorption experiments to understand how water-polymer interactions dictate vapor/liquid transport, determine theoretical limit of water uptake and vapor sorption rate, and optimize the rational designs of desiccant dimensional and material properties. Later, we will optimize geometric parameters of TPMS HEXs via CFD method, prepare TCD coated TPMS HEXs, and evaluate and optimize their adsorption and regeneration characteristics. Finally, we will prototype new desiccant heat pumps with developed TCD coated TPMS HEXs, and evaluate their dehumidification efficiency and energy-saving performance in a confined room. We anticipate our numerical tools and novel prototypes will offer great potential for energy-efficient building dehumidification and air-conditioning systems.