Research ArticleENGINEERING

Water vapor capturing using an array of traveling liquid beads for desalination and water treatment

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Science Advances  12 Apr 2019:
Vol. 5, no. 4, eaav7662
DOI: 10.1126/sciadv.aav7662
  • Fig. 1 Water flow regimes.

    Water flowing down a cotton thread with a diameter of 0.76 mm at flow rates of (A) m.Lps = 0.015 to 0.06 g/s, resulting in the Rayleigh-Plateau instability regime, where beads have constant velocities and spacings, and (B) m.Lps = 0.11 g/s, generating a flow in the convective instability regime that features bead coalescence (Nozzle inner diameter = 0.8 mm).

  • Fig. 2 Mathematical and numerical modeling.

    (A) Schematic of a cotton thread with radius Rs and average roughness λ. (B) Comparison of the experimentally obtained liquid profile and the results obtained from the full Navier-Stokes numerical simulation (string diameter Ds = 0.76 mm, the nozzle inner diameter = 1.2 mm, liquid mass flow rate m.Lps = 0.12 g/s, and average roughness λ = 0.04 mm). (C) The bead spacing and velocity predicted from full Navier-Stokes numerical simulation compared with experimental results (Ds = 0.76 mm, nozzle inner diameter = 1.2 mm, m.Lps = 0.04 to 0.12 g/s, and λ = 0.04 mm). (D) Spatial branches in the complex k-plane from the Orr-Sommerfeld (OS) analysis for a liquid flow rate of 0.141 g/s, string diameter of 0.76 mm, effective slip length of 0.04 mm, and ωi = 0. (E) The absolute and convective instability regimes in the parameter plane of the flow rate versus the string radius. The solid line corresponds to the OS solutions with roughness-induced boundary slip, and the dashed line corresponds to the no-slip case. The circle and cross symbols represent the regularly and irregularly spaced liquid beads observed in the experiments, respectively.

  • Fig. 3 Experimental mass transfer conductance.

    (A) Schematic of the control volume used to develop the governing mass and energy balance equations for the dehumidifier. (B) Mass transfer conductance and bead spacing as a function of the liquid flow rate per string under two different air stream velocities (Vair = 0.38 and 0.68 m/s).

  • Fig. 4 Mass transfer conductance.

    (A) Schematic illustrating the decomposition of the water film into two components: (i) each water bead as a sphere in a uniform air stream of velocity Vair + Vbead (to account for the bead velocity) and (ii) a stationary water cylinder with the same diameter as the liquid substrate coating the string in a uniform air stream of velocity Vair. (B) The experimental and predicted mass transfer conductances as a function of the superficial air velocity for the dehumidifier with 96 strings. Various sets of data are presented for different water flow rates per string, m.Lps. The liquid flows are all in the RP regime. The symbols represent the experimental results, and the lines represent the model predictions. (C) The estimated mass transfer rate (in kg of water/s) to the total interfacial area of (i) liquid beads or (ii) the liquid substrate.

  • Fig. 5 Overall performance and pressure drop.

    (A) Pressure drop as a function of the superficial air velocity for the dehumidifiers with 52 and 96 strings. Symbols represent the experimental data, and the lines represent the model results. (B) Comparison of the mass transfer rate per volume as a function of the air pressure drop per length of dehumidifier. We compare our geometric configuration with previously reported dehumidifier designs, such as flat plate (34), bubble column (35), plate tube (36), and shell and tube (37). deh, dehumidifier.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/4/eaav7662/DC1

    Section S1. Full Navier-Stokes numerical simulation

    Section S2. Mass transfer conductance of water substrate

    Section S3. Air side pressure drop model

    Section S4. Effectiveness, heat flux, and overall performance comparison

    Fig. S1. Spatiotemporal diagram.

    Fig. S2. Numerical simulation domain.

    Fig. S3. Axial temperature profiles of the water and air streams.

    Fig. S4. The effect of the flow regimes on mass transfer.

    Fig. S5. Dynamics of water films flowing in countercurrent flows of air.

    Fig. S6. Effectiveness and heat flux of dehumidifier.

    Fig. S7. Experimental setup.

    Table S1. Dehumidifier comparison.

    References (3840)

  • Supplementary Materials

    This PDF file includes:

    • Section S1. Full Navier-Stokes numerical simulation
    • Section S2. Mass transfer conductance of water substrate
    • Section S3. Air side pressure drop model
    • Section S4. Effectiveness, heat flux, and overall performance comparison
    • Fig. S1. Spatiotemporal diagram.
    • Fig. S2. Numerical simulation domain.
    • Fig. S3. Axial temperature profiles of the water and air streams.
    • Fig. S4. The effect of the flow regimes on mass transfer.
    • Fig. S5. Dynamics of water films flowing in countercurrent flows of air.
    • Fig. S6. Effectiveness and heat flux of dehumidifier.
    • Fig. S7. Experimental setup.
    • Table S1. Dehumidifier comparison.
    • References (3840)

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    Files in this Data Supplement:

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