scholarly journals Evaluation of continuous water vapor δD and δ<sup>18</sup>O measurements by off-axis integrated cavity output spectroscopy

2012 ◽  
Vol 5 (2) ◽  
pp. 2821-2855 ◽  
Author(s):  
N. Kurita ◽  
B. D. Newman ◽  
L. J. Araguas-Araguas ◽  
P. Aggarwal
Keyword(s):  
Water Vapor ◽  
Temporal Resolution ◽  
Isotopic Ratio ◽  
New Technology ◽  
Coupled System ◽  
Calibration Procedure ◽  
Cold Trap ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Accuracy And Precision

Abstract. Recent commercially available laser spectroscopy systems enabled us to continuously and reliably measure the δD and δ18O of atmospheric water vapor. The use of this new technology is becoming popular because of its advantages over the conventional approach based on cold trap collection. These advantages include much higher temporal resolution/continuous monitoring and the ability to make direct measurements of both isotopes in the field. Here, we evaluate the accuracy and precision of the laser based water vapor isotope instrument through a comparison of measurements with those found using the conventional cold trap method. A commercially available water vapor isotope analyzer (WVIA) with the vaporization system of a liquid water standard (Water Vapor Isotope Standard Source, WVISS) from Los Gatos Research (LGR) Inc. was used for this study. We found that the WVIA instrument can provide accurate results if: (1) correction is applied for time-dependent isotope drift, (2) normalization to the VSMOW/SLAP scale is implemented, and (3) the water vapor concentration dependence of the isotopic ratio is also corrected. In addition, since the isotopic value of water vapor generated by the WVISS is also dependent on the concentration of water vapor, this effect must be considered to determine the true water vapor concentration effect on the resulting isotope measurement. To test our calibration procedure, continuous water vapor isotope measurements using both a laser instrument and a cold trap system were carried out at the IAEA Isotope Hydrology Laboratory in Vienna from August to December 2011. The calibrated isotopic values measured using the WVIA agree well with those obtained via the cold trap method. The standard deviation of the isotopic difference between both methods is about 1.4‰ for δD and 0.28‰ for δ18O. This precision allowed us to obtain reliable values for d-excess. The day-to-day variation of d-excess measured by WVIA also agrees well with that found using the cold trap method. These results demonstrate that a coupled system, using commercially available WVIA and WVISS instruments can provide continuous and accurate isotope data, with results achieved similar to those obtained using the conventional method, but with drastically improved temporal resolution.

scholarly journals Evaluation of continuous water vapor δD and δ<sup>18</sup>O measurements by off-axis integrated cavity output spectroscopy

2012 ◽  
Vol 5 (8) ◽  
pp. 2069-2080 ◽  
Author(s):  
N. Kurita ◽  
B. D. Newman ◽  
L. J. Araguas-Araguas ◽  
P. Aggarwal
Keyword(s):  
Water Vapor ◽  
Temporal Resolution ◽  
Isotopic Ratio ◽  
New Technology ◽  
Coupled System ◽  
Calibration Procedure ◽  
Cold Trap ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Accuracy And Precision

Abstract. Recent commercially available laser spectroscopy systems enabled us to continuously and reliably measure the δD and δ18O of atmospheric water vapor. The use of this new technology is becoming popular because of its advantages over the conventional approach based on cold trap collection. These advantages include much higher temporal resolution/continuous monitoring and the ability to make direct measurements of both isotopes in the field. Here, we evaluate the accuracy and precision of the laser based water vapor isotope instrument through a comparison of measurements with those found using the conventional cold trap method. A commercially available water vapor isotope analyzer (WVIA) with the vaporization system of a liquid water standard (Water Vapor Isotope Standard Source, WVISS) from Los Gatos Research (LGR) Inc. was used for this study. We found that the WVIA instrument can provide accurate results if (1) correction is applied for time-dependent isotope drift, (2) normalization to the VSMOW/SLAP scale is implemented, and (3) the water vapor concentration dependence of the isotopic ratio is also corrected. In addition, since the isotopic value of water vapor generated by the WVISS is also dependent on the concentration of water vapor, this effect must be considered to determine the true water vapor concentration effect on the resulting isotope measurement. To test our calibration procedure, continuous water vapor isotope measurements using both a laser instrument and a cold trap system were carried out at the IAEA Isotope Hydrology Laboratory in Vienna from August to December 2011. The calibrated isotopic values measured using the WVIA agree well with those obtained via the cold trap method. The standard deviation of the isotopic difference between both methods is about 1.4‰ for δD and 0.28‰ for δ18O. This precision allowed us to obtain reliable values for d-excess. The day-to-day variation of d-excess measured by WVIA also agrees well with that found using the cold trap method. These results demonstrate that a coupled system, using commercially available WVIA and WVISS instruments can provide continuous and accurate isotope data, with results achieved similar to those obtained using the conventional method, but with drastically improved temporal resolution.

scholarly journals Numerical Simulation of the Water Vapor Separation of a Moisture-Selective Hollow-Fiber Membrane for the Application in Wood Drying Processes

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 593
Author(s):  
Nasim Alikhani ◽  
Douglas W. Bousfield ◽  
Jinwu Wang ◽  
Ling Li ◽  
Mehdi Tajvidi
Keyword(s):  
Water Vapor ◽  
Constant Temperature ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Vacuum Pressure ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Fiber Membrane ◽  
Wood Drying ◽  
Air Velocity

In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.

Degradation of Solid Oxide Fuel Cell Cathodes Accelerated at a High Water Vapor Concentration

2010 ◽  
Vol 7 (2) ◽  
Author(s):  
S. H. Kim ◽  
K. B. Shim ◽  
C. S. Kim ◽  
J. T. Chou ◽  
T. Oshima ◽  
...  
Keyword(s):  
Water Vapor ◽  
Voltage Drop ◽  
Cell Voltage ◽  
High Water ◽  
Solid Oxide ◽  
Constant Current ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Oxide Fuel ◽  
Constant Current Density

The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800°C and 1000°C. Cell voltage change was negligible at 1000°C, while considerable voltage drop was observed at 800°C accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La2O3 formed on the (La0.8Sr0.2)0.98MnO3 surface, which is assumed to be the reason for a large voltage drop.

scholarly journals A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

2018 ◽  
Vol 36 (13) ◽  
pp. 2667-2674 ◽  
Author(s):  
Arun Kumar Mallik ◽  
Gerald Farrell ◽  
Dejun Liu ◽  
Vishnu Kavungal ◽  
Qiang Wu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Low Humidity

Simultaneous water vapor concentration and temperature measurements in unsteady hydrogen flames

2009 ◽  
Vol 32 (2) ◽  
pp. 2527-2534 ◽  
Author(s):  
David Blunck ◽  
Sumit Basu ◽  
Yuan Zheng ◽  
Viswanath Katta ◽  
Jay Gore
Keyword(s):  
Water Vapor ◽  
Temperature Measurements ◽  
Vapor Concentration ◽  
Water Vapor Concentration

Water-vapor Measurements in the Lower Stratosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1527-1531 ◽  
Author(s):  
H. J. Mastenbrook
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Marked Decrease ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Mixing Ratio ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Natural Concentration ◽  
General Range

Nearly 10 years of water-vapor measurements to heights of 30 km provide a basis for assessing the natural concentration of stratospheric water vapor and its variability. The measurements which began in 1964 have been made at monthly intervals from the mid-latitude location of Washington, D.C, using a balloon-borne frost-point hygrometer. The observations show the mixing ratio of water-vapor mass to air mass in the stratosphere to be in the general range of 1 to 4 p.p.m. with a modal concentration between 2 and 3 p.p.m. An annual cycle of mixing ratio is evident for the low stratosphere. A trend of water-vapor increase observed during the first 6 years does not persist beyond 1969 or 1970. The 6 year increase was followed by a marked decrease in 1971, with mixing ratios remaining generally below 3 p.p.m. thereafter. The measurements of recent years suggest that the series of observations may have begun during a period of low water-vapor concentration in the stratosphere.

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