Condensation pressures in small pores: An analytical model based on density functional theory Metadata

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Title

  • Main Title Condensation pressures in small pores: An analytical model based on density functional theory

Creator

  • Author: Nilson, R. H.
    Creator Type: Personal
  • Author: Griffiths, S. K.
    Creator Type: Personal

Contributor

  • Sponsor: United States. Department of Energy.
    Contributor Type: Organization
    Contributor Info: US Department of Energy (United States)

Publisher

  • Name: Sandia National Laboratories
    Place of Publication: Albuquerque, New Mexico
    Additional Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA

Date

  • Creation: 1999-02-01

Language

  • English

Description

  • Content Description: Adsorption and condensation are critical to many applications of porous materials including filtration, separation, and the storage of gases. Integral methods are used to derive an analytical expression describing fluid condensation pressures in slit pores bounded by parallel plane walls. To obtain this result, the governing equations of Density Functional Theory (DFT) are integrated across the pore width assuming that fluid densities within adsorbed layers are spatially uniform. The thickness, density, and energy of these layers are expressed as composite functions constructed from asymptotic limits applicable to small and large pores. By equating the total energy of the adsorbed layers to that of a liquid-full pore, the authors arrive at a closed-form expression for the condensation pressure in terms of the pore size, surface tension, and Lennard-Jones parameters of the adsorbent and adsorbate molecules. The resulting equation reduces to the Kelvin equation in the large-pore limit. It further reproduces the condensation pressures computed by means of the full DFT equations for all pore sizes in which phase transitions are abrupt. Finally, in the limit of extremely small pores, for which phase transitions may be smooth and continuous, this simple analytical expression provides a good approximation to the apparent condensation pressure indicated by the steepest portion of the adsorption isotherm computed via DFT.
  • Physical Description: 18 p.

Subject

  • Keyword: Pressure Dependence
  • Keyword: Pore Structure
  • Keyword: Storage
  • Keyword: Filtration
  • Keyword: Separation Processes
  • Keyword: Porous Materials
  • Keyword: Adsorption
  • Keyword: Gases
  • STI Subject Categories: 32 Energy Conservation, Consumption, And Utilization
  • Keyword: Surface Tension
  • Keyword: Phase Transformations
  • Keyword: Analytical Solution
  • Keyword: Vapor Condensation

Source

  • Other Information: PBD: 1 Feb 1999

Collection

  • Name: Office of Scientific & Technical Information Technical Reports
    Code: OSTI

Institution

  • Name: UNT Libraries Government Documents Department
    Code: UNTGD

Resource Type

  • Report

Format

  • Text

Identifier

  • Report No.: SAND99-8220
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/751009
  • Office of Scientific & Technical Information Report Number: 751009
  • Archival Resource Key: ark:/67531/metadc706000

Note

  • Display Note: OSTI as DE00751009
  • Display Note: Medium: P; Size: 18 pages