Water vapor and carbon dioxide species measurements in narrow channels

    Authors

    S. Basu; D. E. Lambe;R. Kumar

    Comments

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    Abbreviated Journal Title

    Int. J. Heat Mass Transf.

    Keywords

    TDLAS; Narrow channels; Laser diagnostics; Species concentration; PEM FUEL-CELL; IN-SITU; DIODE-LASER; PARTIAL-PRESSURE; ABSORPTION-SPECTROSCOPY; WAVELENGTH MODULATION; TEMPERATURE; SYSTEMS; MICROCHANNELS; TECHNOLOGY; Thermodynamics; Engineering, Mechanical; Mechanics

    Abstract

    Classical spectroscopic techniques have been applied in a novel manner to measure the concentration of gas species, water vapor and carbon dioxide, within a narrow channel flow field non-invasively. Tunable diode laser absorption spectroscopy (TDLAS) was used in conjunction with a laser modulated at a high frequency [Wavelength Modulation Spectroscopy (WMS)] tuned to the ro-vibrational transition of the species. This technique measures the absorption profile which is a strong function of the species concentration across short path lengths and small time spans, as in PEM fuel cells during high load cycles. This method has been verified in a transparent circular flow 12 cm path length and a 12 mm rectangular flow channel. Distinct absorption peaks for water vapor and carbon dioxide have been identified, and concentrations of water vapor and carbon dioxide within the test cells have been measured in situ with high temporal resolutions. A comparison of the full-width at half-maximum (FWHM) of the absorption line-shapes to the partial pressure of water vapor and carbon dioxide showed strong relationships, except in the lower partial pressure regions. Test section temperature was observed to have very minimal impact on these curves at low partial pressure values. A porous media like a membrane electrode assembly (MEA) similar to those used in PEM fuel cells sandwiched between two rectangular flow channels was also tested. Some of the scattered radiation off the MEA was observed using a photodiode at high gain, allowing for more localized species detection. The technique was used to monitor the humidity on either side of the MEA during both temperature controlled and super-saturated conditions. The measurements were observed to be repeatable to within 10%. (C) 2009 Elsevier Ltd. All rights reserved.

    Journal Title

    International Journal of Heat and Mass Transfer

    Volume

    53

    Issue/Number

    4

    Publication Date

    1-1-2010

    Document Type

    Article

    Language

    English

    First Page

    703

    Last Page

    714

    WOS Identifier

    WOS:000273907800014

    ISSN

    0017-9310

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