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Journal ArticleDOI

Effect of the fluid-wall interaction on freezing of confined fluids: Toward the development of a global phase diagram

14 Jun 2000-Journal of Chemical Physics (American Institute of PhysicsAIP)-Vol. 112, Iss: 24, pp 11048-11057
TL;DR: In this article, the effect of the fluid-wall interaction energy on the shift of the freezing temperature and on the fluid structure is considered, using a novel approach to calculate the free energy surface based on Landau theory and order parameter formulation.
Abstract: We report molecular simulation studies of the freezing behavior of fluids in nano-porous media. The effect of confinement is to induce spatial constraints as well as energetic heterogeneity on the confined fluid, thereby altering the bulk phase behavior drastically. We consider the effect of the fluid-wall interaction energy on the shift of the freezing temperature and on the fluid structure, using a novel approach to calculate the free energy surface based on Landau theory and order parameter formulation. Corresponding states theory is then used to map out the global freezing behavior of a Lennard-Jones (LJ) fluid in model slit-shaped pores of varying fluid-wall interaction strengths. Using LJ parameters fitted to thermophysical property behavior, we predict the qualitative freezing behavior for a variety of fluids and nano-porous materials, based on a global freezing diagram. We have attempted to verify these predictions by comparing with experimental data for several systems, and show that in these cases, the experimental observations and the predictions are in agreement.

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Citations
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Dissertation
01 Jan 2012
TL;DR: In this article, a thermal analysis technique utilizing differential scanning calorimetry (DSC) was proposed to approximate the thickness of the adsorbed layer at the liquid-solid interface, a value that has previously only been obtained using simulation or transmission electron microscopy.
Abstract: In concentrated solar power (CSP) systems, high temperature heat transfer fluids (HTFs) are responsible for collecting energy from the sun at the solar receiver and transporting it to the turbine where steam is produced and electricity is generated. Unfortunately, many high temperature HTFs have poor thermal properties that inhibit this process, including specific heat capacities which are half that of water. In an effort to enhance the effective heat capacity of these high temperature HTFs and thus increase the efficiency of the CSP systems, adsorption energy at the liquid-solid interface was investigated as a mechanism for increased thermal capacity. Solid ceramic nanoparticles were dispersed in several molten salts at 1-2% by mass with diameters ranging from 5 nm to 15 nm to provide a significant available surface area for adsorption at the particle-molten salt interface. After successful nanofluid synthesis, differential scanning calorimetry (DSC) was used to measure anomalous deviations from the expected heat capacity and enthalpy of fusion values in the nanofluids. The variation in the sensible and latent heat values was determined to be dependent on the presence of sub-100 nm particles and attributed to a layer of salt that remains adsorbed to the surface of the nanoparticles after the bulk of the salt has melted. The adsorbed salt layer is expected to desorb at a higher temperature, providing an increased effective thermal capacity in the vicinity of this desorption temperature. A thermal analysis technique utilizing DSC was proposed to approximate the thickness of the adsorbed layer at the liquid-solid interface, a value that has previously only been obtained using simulation or transmission electron microscopy. More specifically, the adsorbed layer of LiNO3 on Al2O3 particles was determined to be 5.3-7.1 nm thick, similar to the 1-3 nm layers that have been observed in literature for simple, monatomic fluids. The results provide new insight into the nature of adsorption at the liquid-solid interface in more complex fluid and particle systems that can be harnessed for enhanced thermal capacity in HTFs.

12 citations


Cites background from "Effect of the fluid-wall interactio..."

  • ...Literature provides two criteria for increasing the thickness of the interfacial layer: choose a fluid that is more complex than a simple monatomic fluid [5] and choose a particle that exhibits a strong attraction to the fluid [14]....

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  • ...In Monte Carlo and MD simulations, adsorbed layers on a solid substrate have been shown to melt at a higher, similar, or lower temperature based on whether the attraction of the adsorbate to the substrate is stronger, comparable, or weaker than the attraction to the bulk liquid, respectively [14], [39]....

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  • ...have made efforts to quantify the relative attraction of an adsorbed layer to the substrate versus the bulk liquid [14]....

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  • ...Reports in literature confirm that these ceramics have been shown to sustain an ordered adsorbed layer when in contact with certain liquids, making them a good candidate for the experiments in this thesis [14], [37]....

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  • ...With a high heat capacity HTF, either the size of the plant's solar collectors can be reduced at the same energy output, reducing the material cost of the plant, or more steam and thus more electricity can be extracted from the same amount of HTF [5], [14], [15]....

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Journal ArticleDOI
TL;DR: In this paper, the set pressure in pressure relief valves (PRVs) varying with the type of sealed medium has been a puzzling problem in the field of chemical machinery and equipment for many years.

12 citations

Journal ArticleDOI
TL;DR: In this article, the effect of interfacial layer on water flow in nanochannels was quantitatively studied using Lattice Boltzmann method (LBM) using pore-throat nanochannel model.
Abstract: A novel interfacial model was proposed to understand water flow mechanism in nanochannels. Based on our pore-throat nanochannel model, the effect of interfacial layer on water flow in nanochannels was quantitatively studied using Lattice Boltzmann method (LBM). It is found that both the permeability of nanochannel and water velocity in the nanochannel dramatically decrease with increasing the thickness of interfacial layer. The permeability of nanochannel with pore radius of 10 nm decreases by about three orders of magnitude when the thickness of interfacial layer is changed from 0 nm to 3 nm gradually. Furthermore, it has been demonstrated that the cross-section shape has a great effect on the water flow inside nanochannel and the effect of interfacial layer on the permeability of nanochannel has a close relationship with cross-section shape when the pore size is smaller than 12 nm. Besides, both pore-throat ratio and throat length can greatly affect water flow in nanochannels, and the influence of interfacial layer on water flow in nanochannels becomes more evident with increasing pore-throat ratio and throat length. Our theoretical results provide a simple and effective method to study the flow phenomena in nano-porous media, particularly to quantitatively study the interfacial layer effect in nano-porous media.

11 citations

Journal ArticleDOI
01 Apr 2015-Carbon
TL;DR: In this paper, X-ray scattering measurements provided detailed information on the coexisting state and can be used to study the temperature dependence of the phase behavior of the methane-water system during hydration formation in nanospaces.

11 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the fluid wall interactions and their contributions at the approach of the glass transition of a simple molecular liquid, toluene, and propose to learn about the pore filling processes from adsorption experiments at high temperature.
Abstract: Confinement of glass-forming liquids in nanoporous materials was previously suggested to provide information on the growing heterogeneity length scale responsible of the glass formation. However extensive studies of various liquids under various confinement conditions conclude that the role of surface is dominant over the finite size effects leading to more complex description of the dynamics under confinement. Here we focus on the fluid wall interactions and their contributions at the approach of the glass transition of a simple molecular liquid, toluene. By changing the pore size and the chemistry of the surface, we propose to learn about the pore filling processes from adsorption experiments at high temperature; we relate them to the T-behavior within the pore of a thermodynamic quantity, the averaged density, and the mobility, via the measurements of the mean square displacements over a large T-range where the glass transition spreads out.

11 citations

References
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Book
01 Jan 1954
TL;DR: Molecular theory of gases and liquids as mentioned in this paper, molecular theory of gas and liquids, Molecular theory of liquid and gas, molecular theories of gases, and liquid theory of liquids, مرکز
Abstract: Molecular theory of gases and liquids , Molecular theory of gases and liquids , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

11,807 citations

Book
01 Jan 1995
TL;DR: In this article, the authors present a generalization of the renormalization group of mean field theories, critical phenomena, and topological defects, including walls, kinks and solitons.
Abstract: Preface 1. Overview 2. Structure and scattering 3. Thermodynamics and statistical mechanics 4. Mean-field theory 5. Field theories, critical phenomena, and the renormalization group 6. Generalized elasticity 7. Dynamics: correlation and response 8. Hydrodynamics 9. Topological defects 10. Walls, kinks and solitons Glossary Index.

3,223 citations

Journal ArticleDOI
TL;DR: In this paper, the potential energy of a gas atom interacting with a solid having a surface made up of single type of exposed lattice plane can be expressed as a Fourier series in the position variables in the plane parallel to the surface.

1,379 citations

Journal ArticleDOI
TL;DR: In this paper, the free energy of a Lennard-Jones fluid in the liquid-vapour coexistence region was estimated by relating it to that of the inverse-twelve (soft sphere) fluid, which itself shows no condensation.

1,179 citations