Numerical model for non-equilibrium heat and mass exchange in conjugate fluid/solid/porous domains with application to evaporative cooling and drying

Khan, Furqan Ahmad; Fischer, Christian; Straatman, Anthony G.

doi:10.1016/j.ijheatmasstransfer.2014.09.051

Cited by 21 publications

(31 citation statements)

References 33 publications

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“…Porous media are heterogeneous materials composed of a solid microstructure (or matrix) and a fluid that fills the space unoccupied by the matrix. The structure and the material of the porous media play an important role in the physical behaviour of the media and in the interaction of the matrix with the fluid phase [1]. Considering their usefulness in applications including, for example, heat exchange, a full portrayal of their physical properties is necessary so that they can be adequately modelled in conjunction with other phenomena.…”

Section: Background Information About Porous Mediamentioning

confidence: 99%

The development and numerical modelling of a Representative Elemental Volume for packed sand

Thabet

Straatman

2018

Chemical Engineering Science

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The motivation of this thesis is the development of simple microscopic-scale model (representative elemental volume; REV) that can be used to conduct flow and heat transfer simulations from which closure coefficients can be established for the volume-averaged transport equations for porous media (packed bed). The thesis provides a brief introduction to the computational technique adopted for the geometric generation of the REV (YADE), followed by a parametric study undertaken to reveal the minimum number of particles inside the REV that are required to mimic the appropriate physics. Additional analysis was conducted with the goal of determining the influence of deviation in particle diameter. A wide range of particle temperatures was considered for analyzing the convective heat transfer and hydrodynamic behavior such the influence of property variation on temperature could also be studied. The key research output is a detailed comparison of the results related to the hydrodynamics and heat transfer closures produced by an idealized, YADE-generated model against a three-dimensional, digitized model of packed sand. It is shown that the YADE model gives results that are in very good agreement with the digitized packed-sand model in the range of Reynolds numbers considered. The YADE model results were then compared with experimental findings and it was found that while the trends in convective heat transfer were well-predicted, there was a difference in the magnitude of the convective coefficients predicted and measured in previous experiments.

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Section: Background Information About Porous Mediamentioning

confidence: 99%

The development and numerical modelling of a Representative Elemental Volume for packed sand

Thabet

Straatman

2018

Chemical Engineering Science

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“…The moist air temperature T is obtained by solving its energy transport equation (see Khan et al [33] for further details). Since, the present work is intended for turbulent heat and mass transfer in packed bed of spheres for food storage and refrigeration applications, the present model incorporates non-equilibrium heat and mass transfer inside porous region.…”

Section: The Macroscopic Modelmentioning

confidence: 99%

“…For the case where the available water content is less than the h _ m fs i computed using Eq. (19), h _ m fs i is calculated based on the available water content (see Khan et al [33] for details).…”

Section: The Macroscopic Modelmentioning

confidence: 99%

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Closure of a macroscopic turbulence and non-equilibrium turbulent heat and mass transfer model for a porous media comprised of randomly packed spheres

Khan

Straatman

2016

International Journal of Heat and Mass Transfer

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“…changes with change of boundary conditions. Local exchanges of heat and mass between the phases of porous materials have also been studied, however, generally they have been ignored in equilibrium-type models, or they are empirically adjusted for non-equilibrium models [24,25]. Particle and grain packed-bed studies have given the subject more practical interest mainly in terms of the dynamic nature of the change in mass transfer resistances that is more pertinent in these studies [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Dynamic coupling of phase-heat and mass transfer in porous media and conjugate fluid/porous domains

Elhalwagy

Straatman

2017

International Journal of Heat and Mass Transfer

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A dynamically varying technique for phase heat and mass transfer in porous media and fluid/porous domains has been developed and incorporated into a conjugate finite volume CFD framework. The local interstitial phase mass exchange within porous zones is estimated by comparison of the resistances to moisture transport within the solid and void constituents of the porous material; the higher resistance expression being used as rate-determining. Based on the mass transfer expression, a local estimate of the Biot number is used to physically apportion the withdrawal of vaporization energy from the solid and fluid constituents of the porous medium. A similar approach is used for coupling of the clear fluid and porous CFD cells at the clear fluid/porous interface. A phase ratio concept is introduced at these interfaces to be able to couple the different phases in heat and mass transfer. The model is generic, involving details that allow application to a wide range of cases and is one of the least empirically-adjusted models. The microscopic coupling approach has been validated for Coal packed bed drying. Results show good agreement with experimental data in terms of the matching trends and the small margins for temporal moisture and temperature variation. The macroscopic coupling technique has been tested using the cases of drying of an apple slice and the dehydration of mineral plaster. Investigating the two cases showed a clear difference in behavior as the apple slice case is material-side-resistance dominant-i.e. diffusively dominant-and the plaster case is air-side-resistance dominant-i.e. convectively dominant. The results are physically reasonable and compare well to available experiments and reported results from the literature. The comparisons indicate the capability of the present approach to model the dynamic coupling accurately in a computationally time-efficient manner.

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Numerical model for non-equilibrium heat and mass exchange in conjugate fluid/solid/porous domains with application to evaporative cooling and drying

Cited by 21 publications

References 33 publications

The development and numerical modelling of a Representative Elemental Volume for packed sand

The development and numerical modelling of a Representative Elemental Volume for packed sand

Closure of a macroscopic turbulence and non-equilibrium turbulent heat and mass transfer model for a porous media comprised of randomly packed spheres

Dynamic coupling of phase-heat and mass transfer in porous media and conjugate fluid/porous domains

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