The Thermodynamics of Air-Water Vapor Mixtures

2000 ◽  
Author(s):  
George A. Adebiyi
Keyword(s):  
Water Vapor ◽  
Thermodynamic Analysis ◽  
Ambient Air ◽  
Moist Air ◽  
Humidity Ratio ◽  
Atmospheric Air ◽  
Analysis And Evaluation ◽  
Vapor Mixtures ◽  
Reference Environment ◽  
Traditional Approaches

Abstract Traditional approaches to the thermodynamic analysis of processes involving air-water vapor mixtures are often limited to a psychrometric analysis and a first-law analysis. The substances involved are moist air (a mixture of dry air and moisture), and water (either as vapor, or as a liquid). A complete thermodynamic analysis must, however, include a second-law analysis. This article presents a complete outline for the thermodynamic analysis and evaluation of processes involving air-water vapor mixtures. With regards to exergy analysis, in particular, it is noted that the published and widely accepted equation for the exergy of moist air is indeterminate when the humidity ratio of the ambient air is zero. This raises questions about the appropriate reference environment for water or water vapor when the atmospheric air does not contain moisture. The alternative of an expanded reference environment, which includes a large pool of water co-existing with ambient air is proposed in this article. The resulting equations for the exergy of moist air are determinate regardless of the humidity ratio of the atmospheric air in the reference environment.

The Effect of Humidity on the Thermodynamic Behaviour of Atmospheric Air

1999 ◽  
Author(s):  
D. A. Kouremenos ◽  
X. K. Kakatsios ◽  
R. N. Krikkis
Keyword(s):  
Practical Interest ◽  
Ideal Gas ◽  
The State ◽  
State Variables ◽  
Moist Air ◽  
Humidity Ratio ◽  
Atmospheric Air ◽  
Thermodynamic Behaviour ◽  
Impulse Function ◽  
Wide Range

Abstract The present work considers the thermodynamic behaviour of moist air as a function of the state variables temperature, density and humidity ratio. Moist air is treated as an ideal mixture which is composed of two real gases, air and steam. The state functions of the mixture are expressed using the corresponding explicit relations of the two species from which the three isentropic exponents describing the real gas isentropic change are calculated. Saturated conditions are determined by solving the Vapour Liquid Equilibrium problem for real water. Numerical results show the effect of humidity as well as the effect of pressure on the thermodynamic behaviour of atmospheric air (such as the three isentropic exponents kpρ, kTp, kTρ, the classical isentropic exponent k and the velocity of sound) for a wide range of temperatures and pressures. Furthermore the isentropic change is approximated by explicit relations having mathematical forms similar to those of the ideal gas but with different constants and exponents. The obtained accuracy is remarkable, being better than 0.32%. In this way the isentropic change, of moist air can be computed by simple explicit relations having as independent variable the Mach number and the humidity ratio. The effects of humidity are examined on certain cases of practical interest such as the critical state (M = 1), the impulse function and the mass flow rate.

Measurement of Latent Heat by the Gas-Current Method

1942 ◽  
Vol 9 (1) ◽  
pp. A21-A25
Author(s):  
J. A. Goff ◽  
J. B. Hunter
Keyword(s):  
Experimental Data ◽  
Water Vapor ◽  
Latent Heat ◽  
Thermodynamic Analysis ◽  
Current Method ◽  
Interaction Constant ◽  
University Of Pennsylvania ◽  
Scientific School ◽  
Vapor Mixtures ◽  
American Society

Abstract The gas-current method of measuring latent heat appears to possess important advantages over other calorimetric methods. Preliminary results have been derived from a co-operative investigation carried out by the American Society of Heating and Ventilating Engineers and the Towne Scientific School, University of Pennsylvania, in which sufficiently reliable values of the interaction constant for air-and-water-vapor mixtures have been determined to permit an adequate thermodynamic analysis of the gas-current method. The present paper is devoted to the development of this analysis and its application to the reduction of certain experimental data recently obtained by one of the authors. The apparatus and method of conducting the experiments are also described.

Water vapor sorption on Marcellus shale: measurement, modeling and thermodynamic analysis

Fuel ◽  
2017 ◽  
Vol 209 ◽  
pp. 606-614 ◽  
Author(s):  
Xu Tang ◽  
Nino Ripepi ◽  
Katherine A. Valentine ◽  
Cigdem Keles ◽  
Timothy Long ◽  
...  
Keyword(s):  
Water Vapor ◽  
Thermodynamic Analysis ◽  
Marcellus Shale ◽  
Water Vapor Sorption ◽  
Vapor Sorption

scholarly journals Water Vapor Sorption Characteristics of Powder Type Organic Sorbent in a Moist Air Fluidized Bed.

2001 ◽  
Vol 67 (660) ◽  
pp. 2105-2112 ◽  
Author(s):  
Hideo INABA ◽  
Takahisa KIDA ◽  
Akihiko HORIBE ◽  
Kiyohiro KAMEDA ◽  
Tamio OKAMOTO ◽  
...  
Keyword(s):  
Water Vapor ◽  
Fluidized Bed ◽  
Water Vapor Sorption ◽  
Vapor Sorption ◽  
Moist Air ◽  
Powder Type ◽  
Sorption Characteristics

Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells

2007 ◽  
Vol 1041 ◽  
Author(s):  
Seon Hye Kim ◽  
Toshihiro Ohshima ◽  
Yusuke Shiratori ◽  
Kohei Itoh ◽  
Kazunari Sasaki
Keyword(s):  
Water Vapor ◽  
Solid Oxide Fuel Cells ◽  
Degradation Mechanism ◽  
Chemical Species ◽  
Cell Voltage ◽  
Ambient Air ◽  
Open Circuit ◽  
Constant Current ◽  
Constant Current Density

AbstractAmbient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.

Preparation of matched reagents for use with the Scholander gas analyzer

1977 ◽  
Vol 43 (1) ◽  
pp. 164-166
Author(s):  
R. G. Collins ◽  
V. W. Musasche ◽  
E. T. Howley
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Volume Change ◽  
Quantitative Method ◽  
Gas Analysis ◽  
Vapor Pressures ◽  
Gas Analyzer ◽  
Atmospheric Air ◽  
Fixed Acid

Scholander's method of gas analysis requires that the solutions for CO2 absorber, O2 absorber, and acid-rinse be matched in terms of water vapor tension throughout the analysis. Any difference in vapor pressure between either or both of the absorbing solutions and the indicator drop (composed of acid-rinse) will produce a measurable volume change which cannot be attributed to the presence of absorbable gases. This paper describes a practical and quantitative method for preparing reagents whose vapor pressures are matched. A fixed acid-rinse formulation was used throughout. A CO2 absorber prepared from 1.35 N KOH and an O2 absorber prepared from 0.76 N KOH were both matched in terms of vapor pressure with Scholander's acid-rinse solution. Analysis of atmospheric air provided a check on the accuracy of the technique. The values obtained were O2 20.94%, CO2 0.03%, and N2 (balance) 79.04%.

scholarly journals The lightness of water vapor helps to stabilize tropical climate

2020 ◽  
Vol 6 (19) ◽  
pp. eaba1951 ◽  
Author(s):  
Seth D. Seidel ◽  
Da Yang
Keyword(s):  
Water Vapor ◽  
Longwave Radiation ◽  
Tropical Climate ◽  
Climate Feedback ◽  
Tropical Atmosphere ◽  
Radiative Effect ◽  
Buoyancy Effect ◽  
Moist Air ◽  
Dry Air ◽  
Earth’S Climate

Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin.

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