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Solid desiccant humidity pump is an emerging device that enables moisture transport through the inverse gradient of vapor concentration, featuring refrigerant-free, no moveable parts and compact structure. However, traditional materials (e.g. silica gel and zeolite) have made this device less competent due to the poor sorption performance and strict regeneration conditions. In this respect, metal-organic frameworks, representing the cutting edge of the available porous materials, are expected to upgrade the performance of this device. In this study, the optimization of a novel MOF-based humidity pump (MOF-HP) was carried out. We used the CFD method to analyze the hygrothermal performance of a MOF-HP. The model built up the relationship among humid air, desiccant, and heat sink and then coupled the subdomains of the fluid flow, heat transfer, and specie transport. The model of MOF-HP under different operation conditions was validated by experimental tests. Based on the measured results, the discrepancies were maintained under 15%. A parametric optimization was subsequently carried out to enhance the hygrothermal performance of MOF-HP. This dimensional analysis provides some guidelines for MOF-HP design with the most suitable geometry. The optimized configuration is estimated to have a 1.59 times improvement in moisture removal capacity over the original design. • A novel MOF humidity pump is constructed for energy-efficient localized moisture control. • A CFD approach is adopted to optimize the geometry and performance of MOF-HP. • The governing equations (i.e., mass, momentum, energy and species conservation) are highly coupled. • Parametric study discloses the correlation between the fluid flow and the mass transport. • The optimized configuration is estimated to have a 1.59 times improvement in moisture removal capacity. [ABSTRACT FROM AUTHOR]

Combined heat, air, and moisture transport between building envelopes and indoor air has a significant effect on indoor thermal and humidity conditions, energy performance of buildings, indoor air quality, durability of constructions, etc. The article presents an analytical method to calculate combined hygrothermal transfer in porous building materials under different boundary conditions, which include the convection surface, adiabatic surface, constant heat and moisture potential surface, etc. An improved Luikov's equation was adopted to describe the heat and moisture transfer in porous media. The interactions between heat and moisture transport were modeled by introducing the temperature gradient coefficient. The governing equations were subjected to the Laplace transformation first, then solved by the transfer function method in the Laplace domain. The inversion theorems for the Laplace transformation were applied to all boundary conditions to get the final results in the time domain. The results were compared with the measured values and numerical solutions obtained from previous studies; good agreement was obtained. The analytical solutions can be used to develop a simpler algorithm for the quick evaluation of heat, air, and moisture transfer in building applications when the diurnal temperature variation is less than 10°C and the relative humidity variation is between 10% and 90% [ABSTRACT FROM PUBLISHER]

In this paper, an analytical method utilizing the transfer function method has been proposed to evaluate the thermal and moisture transfer behavior in porous building material. Both heat and moisture transfer are simultaneously considered and their interactions are modeled. The coupled partial differential equations and boundary conditions are first subjected to Laplace transformation, and then the equations are solved by introducing the transfer function method. The transient temperature and moisture content distribution across the building material can thus be easily obtained from the solutions. The results are compared with the experimental data and the other numerical solution available in the literature. A good agreement is obtained. [ABSTRACT FROM AUTHOR]

The regulation of the balance of the sensible and latent loads remains a critical problem for built environment control. Unlike the traditional vapor compression system that features high-energy consumption and environmental-unfriendly processes, desiccants represent an alternative air-conditioning method that takes advantage of the low-grade energy, decreases the energy consumption and even employs use of water vapor. Though the desiccant-based systems can achieve spatial moisture transfer through the periodic adsorption/desorption process, however, the water-stable desiccants with high water uptake and mildly reversible adsorption are required, and the traditional desiccants cannot meet these requirements. In this respect, metal-organic frameworks (MOFs), possessing a variety of structures and precise functional ability to optimize their properties, are promising porous materials exhibiting high potential for rational design and sorption-based applications. In this review, intrinsic properties and prevalent water adsorption mechanisms of the potential micro/mesoporous MOF desiccants have been elucidated. Subsequently, the selection criteria of the promising MOF desiccants for water loading removal from air in the built environment is proposed and some currently available water-stable MOFs based on different working humidity ranges have been analyzed for the potential humidity control from the aspects of microstructure, isotherms and regeneration conditions. Finally, approaches for screening the well-suited MOFs from material and system levels is presented. Overall, the cases of actual applications in the active or passive way have confirmed that MOF-based systems can effectively regulate the humidity load within the desirable range, thus, underlining the high potential of large-scale applications in the near future. • Research on MOF materials for the built environment control has been reviewed. • Special crystal structure of MOF plays an important role in the adsorption mechanism. • Selection criteria and classification of MOFs disclose the potential application in solid desiccant systems. • Development of MOF commercialization and system-related technologies are prospected. [ABSTRACT FROM AUTHOR]