Heat and mass transfer in hygroscopic hydrogels

Journal Article · Sat Jun 18 00:00:00 EDT 2022 · International Journal of Heat and Mass Transfer

DOI:https://doi.org/10.1016/j.ijheatmasstransfer.2022.123103· OSTI ID:1875106

Díaz-Marín, Carlos D. ^[1]; Zhang, Lenan ^[2]; Fil, Bachir El ^[2]; Lu, Zhengmao ^[2]; Alshrah, Mohammed ^[2]; Grossman, Jeffrey C. ^[2]; Wang, Evelyn N. ^[2]

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1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); MIT
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sorption and desorption with hygroscopic hydrogels hold significant promise for thermal management, passive cooling, thermal energy storage, and atmospheric water harvesting. However, a comprehensive understanding of the energy and mass transport mechanisms in hygroscopic hydrogels remains missing, impeding accurate modeling and optimization. In this paper, we develop a model for the simultaneous vapor, water, and heat transfer in hygroscopic hydrogels during sorption and desorption processes. We show that by considering vapor diffusion in the hydrogel micropores, water diffusion in the polymer mesh, and heat transfer in the porous hydrogel, we can accurately capture experimentally observed thermally-driven desorption rates in these hydrogels. Furthermore, we consider three typical operating configurations of hydrogels and elucidate the differences in the transport mechanisms depending on the configuration. Finally, for each of these configurations, we identify key design parameters, including hydrogel thickness, hydrogel shear modulus, heat transfer coefficient, and thermal conductivity, and we parametrically show that by varying these parameters, a hygroscopic hydrogel can desorb up to 128.5%, 14.9%, 69.7%, and 9.6% more water, respectively, relative to the initial water content. This work provides a generic framework to model sorption and desorption processes in hygroscopic hydrogels which can guide the design and optimization in applications of thermal management, passive cooling, thermal energy storage, and atmospheric water harvesting with hydrogels.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
• Sponsoring Organization: Air Force Office of Scientific Research; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
• Grant/Contract Number: EE0009679
• OSTI ID: 1875106
• Journal Information: International Journal of Heat and Mass Transfer, Journal Name: International Journal of Heat and Mass Transfer Vol. 195; ISSN 0017-9310
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Desorption
Heat transfer
Hygroscopic hydrogels
Mass transfer
Sorption
Water