Gas Vapor Pressure Research Articles

Evaluation of an optimal integrated design multi-fuel multi-product electrical power plant by energy and exergy analyses

A novel integrated multi-fuel multi-product electrical power plant with a net electrical power output of 5.97 × 105 kW is developed and investigated by energy and exergy analyses. The electrical power plant including coal gasification, natural gas solid oxide fuel cell, cryogenic air separation unit, carbon dioxide transcritical and steam cycles, and liquefied natural gas regasification sub-systems. The potential of operating performance improvement by conducted energy and exergy analyses is assessed. Also, the thermal design and heat integration analyses are performed for studying the system sustainability and emphasizing on no requirement for external hot and cold utilities. Effects of the main design parameters such as fuel cell operating parameters, ambient temperature and liquefied natural gas thermodynamic specifications on the system operating performance are examined. The obtained results indicate that the overall energy and exergy efficiencies reach to a maximum value of about 56.4% and 57.9%, respectively; in the case of fuel utilization of solid oxide fuel cell is about 80.0%. Furthermore, increasing the ambient temperature and current density decrease the system operating performance. In contrast, the system performance increases with the liquefied natural gas vapor pressure.

Gas-pressure chemical vapor transport growth of millimeter-sized c-BAs single crystals with moderate thermal conductivity

We have grown c-BAs single crystals up to 1000 μm size by the chemical vapor transport (CVT) technique using combined As and I2 transport agents with the As:I ratio of 1:3 under gas pressures of up to 35 atm. Raman spectroscopy revealed a very sharp (∼2.4 cm−1) P1 phonon mode and an interesting splitting behavior of P1 from detailed polarization studies. Electron paramagnetic resonance (EPR) experiments revealed no evidence for EPR active growth-related defects under the experimental resolution. Finally, a moderate thermal conductivity value of ∼132 W/m-K was obtained using a transient thermal grating technique. These results suggest that although the high As gas vapor pressure environment in CVT growth can increase the transport rate of c-BAs significantly, it may not be efficient in reducing the defects and enhancing the thermal conductivity in c-BAs significantly.

Gas-adsorption dynamics at the water–air interface, revealed by resonant droplet tensiometry

A resonant hemispherical pendant droplet tensiometry has been used to register in real time the change of surface tension of low Bond number water droplets due to evaporation of simple volatile liquids, acetone and chloroform, in a closed vessel. The contributions of the gas vapor pressure and of the gas molecules adsorption to the surface tension changes are distinguished and evaluated in time. After the initial increase of gas adsorption, a negative adsorption has been found in later time, which may be informative for the dynamics of the adsorption and desorption processes in the interface layer. The observed desorption processes are stimulated by the mechanical oscillations of the interface layer, as far as the droplet is in resonance during the measurements.

Modeling for Ligand-Capped Metallic Nanoparticles in a Gas-Expanded Liquids System: Surface Fraction Model

Gas-expanded liquids (GXLs) are mixtures of gas dissolved in organic solvents and compressed up to pure gas vapor pressure. GXLs are the most commonly used and investigated class in particle separation processes. By employing both CO2-expanded hexane and ethylene-expanded hexane, gold as well as silver nanoparticles were precipitated at 303 K under various gas pressures ranging from 2.07 to 4.82 MPa. The cascaded-vessel apparatus applied in this study allowed fractionation of nanoparticles into a narrow range of fractions in a faster and dependable manner. The mean sizes of metal particles obtained in a GXL system can be adjusted simply by varying the gas pressure. To investigate the effects of ligand length and surface coverage on the production of precipitates, a thermodynamic model developed for the fractionation of ligand-capped nanoparticles in GXLs was applied. Specifically, a surface fraction model with an effective ligand surface area ratio was employed, and the reliability of the modeling results...

Investigation of the kinetics of the fluidized bed process for the dehydration of NdCl 3·6H 2O, TbCl 3·6H 2O and DyCl 3·6H 2O

Dehydration of NdCl 3·6H 2O, TbCl 3·6H 2O and DyCl 3·6H 2O was carried out by fluidization in a gas mixture of Ar and HCl. In a series of isothermal experiments the effect of different process parameters was considered. Water vapour pressure of gas leaving the fluidized bed was estimated by using a simple mass balance. It was shown that the rate-limiting step of the overall dehydration process in the fluidized bed is removal of water vapour by a saturated bulk gas flow. However, the saturated gas phase data could not be thermodynamically interpreted. The reason to this is discussed.

Influence of reactant gas vapor pressure on the electrical properties and the electroluminescent efficiency of GaAs0.62P0.38

A number of workers have shown that the vapor pressure of the reactant gases strongly influences the electrical properties of GaAs vapor grown in the ASCI3 system. This paper presents the results of a study of the effects of the variation of vapor pressures on GaAs0.62P0.38 grown in the hydride synthesis system. The material was analyzed using Hall effect measurements taken as a function of temperature from room to liquid helium temperatures, and using test electroluminescent diodes. A least squares fit was made to the Hall effect data using a model which includes the effects of two valley conduction to obtain densities of donors and acceptors and donor ionization energies. Increasing reactant gas pressure causes a decrease in donor and acceptor densities as ND, NA∞ P -2.5 which is slower than the P−4 observed by DiLorenzo in the ASCI3 system. The ionization energy of the donors was quite high (100 meV) for the high and low pressures, and were less than 10 meV for the intermediate pressures. Hall mobilities at room and liquid nitrogen temperatures were best for material grown at intermediate pressures and the electroluminescent efficiencies of unencapsulated test diodes increased from 0.05 per cent at the extremes to above 0.1-0.2 per cent at the intermediate pressures. These variations are consistent with varying Si incorporation rate and varying density of point defects with varying reactant gas vapor pressure.

The vapour pressure and thermal stability of gallium sulphide

The vapour pressure of GaS as a function of temperature has been determined. Below the melting point (962°C) the vapour conforms to the relation log P GaS (mm Hg) = − 23190 T + 19.39 and above the melting point to log P GaS (mm Hg) = − 6390 T + 5.74 Calculation of the equilibrium constant for the reaction 2 GaS (s) ⤦ 2 Ga (g) + S 2(g) leads to the expression K GaS = − 55536 T + 24.75 which is in accordance with the experimental results. This equilibrium constant is employed to calculate the minimum values of the p s 2 above GaS at different temperatures. The thermal stability of GaS have also been determined. The results explain the free gallium found in the crystal growth experiments when a carrier gas is used or when large evacuated tubes are employed.