Drying of hygroscopic capillary porous solids —A theoretical approach

Berger, Daniel; Pei, David C. T.

doi:10.1016/0017-9310(73)90058-6

Cited by 83 publications

(31 citation statements)

References 7 publications

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“…Most HAM models use this method [7,21,22]. Berger et al [23] were able to study drying phenomena using a 1D finite difference model with constant heat and mass transfer coefficients as boundary conditions. Furthermore, their study showed that the convective transfer coefficient determined the drying rate during the CRP.…”

Section: Numerical Modelling: Predetermined Transfer Coefficientsmentioning

confidence: 99%

Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD

Belleghem

Steeman

Janssen

et al. 2014

Building and Environment

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Moisture-related damage is an important issue when looking at the performance of building envelopes. In order to accurately predict the moisture behaviour of building components, building designers can resort to Heat, Air and Moisture (HAM) models. In this paper a newly developed heat and mass transfer model that is implemented in a 3D finite volume solver, Fluent®, is presented. This allows a simultaneous modelling approach of both the convective conditions surrounding a porous material and the heat and moisture transport in the porous material governed by diffusion. Unlike most HAM models that often confine to constant convective transport coefficients it is now possible to better predict these convective boundary conditions. An important application of the model is the convective drying of porous building materials. Especially during the first drying stage, the drying rate is determined by the convective boundary conditions. The model was validated against a convective drying experiment from literature, in which a saturated ceramic brick sample is dried by flowing dry air over one side of the sample surface. Temperature and relative humidity measurements at different depths in the sample, moisture distribution profiles and mass loss measurements were compared with simulation results. An overall good agreement between the coupled model and the experiments was found, however, the model predicted the constant drying rate period better than the falling rate period. This was improved by adjusting the material properties. The adjustment of the material properties was supported by neutron radiography measurements.

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Section: Numerical Modelling: Predetermined Transfer Coefficientsmentioning

confidence: 99%

Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD

Belleghem

Steeman

Janssen

et al. 2014

Building and Environment

View full text Add to dashboard Cite

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“…The thermal behaviour of biomass is strongly dependent upon the biochemical composition and structure of the feedstock, and the specific effects of MW heating on biomass has been previously explored [192][193][194]. Within the biomass, not all of the biochemical constituents are able to absorb MWs, and even if they can absorb MWs, the degree of polarisation [183,[195][196][197]. The bulk heating mechanism of microwave irradiation causes water to vaporise within the pores of the biomass, as water dipoles attempt to continuously reorient within the oscillating electric field.…”

Section: Understanding Selective Heating Behaviourmentioning

confidence: 99%

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

Kostas

Beneroso

Robinson

2017

Renewable and Sustainable Energy Reviews

253

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Bioenergy, derived from biomass and/or biological (or biomass-derived) waste residues, has been acknowledged as a sustainable and clean burning source of renewable energy with the potential to reduce our reliance on fossil fuels (such as oil and natural gas). However, many bioenergy processes require some form of pre-treatment and/or upgrading procedure for biomass to generate a modified residue with more suitable properties and render it more compatible with the specific energy conversion route chosen. Many of these pre-treatments (or upgrading procedures) involve some form of substantive heating of the biomass to achieve this modification. Microwave (MW) heating has attracted much attention in recent years due to the advantages associated with dielectric heating effects. These advantages include rapid and efficient heating in a controlled environment, increasing processing rates and substantially shortening reaction times by up to 80%. However, despite this interest, the growth of industrial MW heating applications for bioenergy production has been hindered by a lack of understanding of the fundamentals of the MW heating mechanism when applied to biomass and waste residues. This article presents a review of the current scientific literature associated with the application of microwave heating for both the pre-treatment and upgrading of various biomass feedstocks across different bioenergy conversion pathways including thermal and biochemical processes. The fundamentals behind microwave heating will be explained, as well as discussion of the imperative areas which require further research and development to bridge the gap between fundamental science in the laboratory and the successful application of this technology at a commercial scale.

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“…These models usually take into account some subset of the following transport phenomena: capillary flow of liquid, convective flow and diffusion of gas, and heat transfer by conduction and convection within the body. Most published theoretical investigations have focused primarily on drying phenomena and can be categorized (Berger and Pei, 1973) into four groups: diffusion theory (Sherwood, 1931), capillary flow theory (Ceaglske and Hougen, 1937), evaporation-condensation theory (Gurr et al, 1952), and the application of irreversibIe thermodynamics (Luikov, 1966). These models tend either to be incomplete in their treatment of all transport processes that occur during at least one portion of the drying process or include expressions (e.g., Luikov, 1966) that are difficult to obtain or interpret experimentally.…”

Section: Simultaneous Momentum Heatmentioning

confidence: 99%

Simultaneous momentum, heat and mass transfer with chemical reaction in a disordered porous medium: application to binder removal from a ceramic green body

Stangle

Aksay

1990

Chemical Engineering Science

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Abstract-A theoretical model has been developed to describe simultaneous momentum, heat, and mass transfer phenomena in disordered porous materials. The model can be applied to a wide variety of engineering-related fields, e.g., the drying and/or burnout of processing aids in the colloidal processing of advanced ceramic materials. Simulations based on the model predict the local temperature and mass distribution of the porous body as a function of time and position. This information can then be coupled with known mechanical properties of the body to predict internal stresses generated during removal of liquid from the body. The theoretical model has potential application to many engineering problems, e.g., the optimization of processing conditions in the design of an improved binder removal process. The model is evaluated using experimental data on binder removal from a ceramic green compact consisting of submicron a-Al,O,

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Drying of hygroscopic capillary porous solids —A theoretical approach

Cited by 83 publications

References 7 publications

Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD

Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

Simultaneous momentum, heat and mass transfer with chemical reaction in a disordered porous medium: application to binder removal from a ceramic green body

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