Estimation of Saturated Vapor Pressure from Nucleation Data

Saturated vapor pressure was calculated from the nucleation experimental data using the thermodynamically consistent nucleation theory in which the effect of real gas is considered. The cubic polynomial fit equations of saturation pressure for several substances were obtained based on the calculation. The results of the calculations were compared to those of thermodynamic equilibrium equation and the empirical equation and applied to the predictions of the classical nucleation theory. The results show that the saturation pressures estimated from the nucleation data agree fairly well with those of empirical equations for the substances investigated, and this indicates that the predictions from the classical nucleation theory are close to the experimental data.

The existence of saturated vapors in the deep source region of 2017Pohang earthquake evidenced from seismic tomography

Geothermal resources are a promising approach to clean renewable energy;90%of them are deep reservoirs of hot dry rock that require hydraulic fracturing to create a network of connections among wells to enable efficient heat exchange,known as an Enhanced Geothermal System(EGS).The Pohang EGS project in south Korea led to a devasting Mw5.5 earthquake,triggered by the reservoir's EGS stimulation,the largest earthquake known to have been induced by EGS development.Detailed investigations have been conducted to understand the cause of the Pohang earthquake;the conclusion has been that overpressurized injected fluids migrated into an unknown fault triggering this large earthquake.Detailed velocity images for the source zone of the 2017 Pohang earthquake,which could be helpful for further understanding its inducing mechanism,are unavailable.However,we have assembled detailed aftershock data recorded by 41 local stations installed within about three months after the Mw5.5 Pohang earthquake,and have then applied the V_(p)/V_(s)model's consistency-constrained double-difference seismic tomography method to determine the high-resolution three-dimensional Vp(compressional wave velocity),Vs(shear wave velocity),and V_(p)/V_(s)models of the source region that we report here,as well as earthquake locations within the source region.The velocity images reveal that the deep source area of the 2017 Pohang earthquake is dominated by low Vp,high Vs,and low V_(p)/V_(s)anomalies,a pattern that can be caused by overpressurized vapors due to high temperatures at these depths.Based on aftershock locations and velocity features,our studies support the conclusion that the 2017Pohang earthquake was triggered by injected EGS fluids that migrated into a blind fault.

Dispersion hydrophobic electrolyte enables lithium-oxygen battery enduring saturated water vapor

Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many parasitic reactions,especially related to water.Water is a double-edged sword,which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product.In this work,hexamethyldisilazane(HMDS)is introduced into the electrolyte of an aprotic Li-O_(2) battery.HMDS has a strong ability to combine with a trace of water to gen erate a hydrophobic hexamethyldisiloxa ne(MM),which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water.In this case,the hydrophobic MM disperses in the ether-based electrolyte,forming a dispersion hydrophobic electrolyte.This electrolyte can anchor water from the environment on the cathode side,which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity.Compared with the Li-O_(2) battery without the HMDS,the HMDS-containing Li-O_(2) battery contributes an about 13-fold increase of cyclability(400 cycles,1800 h)in the extreme environment of saturated water vapor.This work opens a new approach for directly operating aprotic Li-O_(2) batteries in ambient air.

Modeling and Simulation of Lithium Vacuum Evaporation Process Using COMSOL Multiphysics

Based on the COMSOL Multiphysics simulation software,this study carried out modeling and numerical simulation for the evaporation process of liquid metal lithium in the vacuum free molecular flow state.The motion of lithium atoms in the evaporation process was analyzed through a succession of studies.Based on the available experimental values of the saturated vapor pressure of liquid metal lithium,the relationship between saturated vapor pressure and temperature of liquid lithium in the range of 600 K-900 K was obtained.A two-dimensional symmetric model(3.5 mm×20 mm) was established to simulate the transient evaporation process of liquid lithium at wall temperatures of 750 K,780 K,800 K,810 K,825 K,and 850 K,respectively.The effects of temperature,the evaporation coefficient,back pressure,and length-to-diameter ratio on the evaporation process were studied;the variation trends and reasons of the molecular flux and the pressure during the evaporation process were analyzed.At the same time,the evaporation process under variable wall temperature conditions was simulated.This research made the evaporation process of liquid lithium in vacuum molecular flow clearer,and provided theoretical support for the space reactor and nuclear fusion related fields.

A New Approach to Investigation of vdW Type of Equations of State

A new approach to the investigation of vdW type of equations of state (EOS) is developed by embedding a vapor pressure equation and a saturated liquid volume equation into vdW type EOS, which results in a new function AS(T). The AS(T) possesses the properties of an attractive parameter A(T), and if an EOS is accurate in the whole PVT space, then its numerical value equals A(T). As a useful tool for investigating EOS, the As(T) has been used to make comparisons among RKS, PRSVII, PT and ALS EOS, and to indicate where the shortcomings of the EOS are coming from. Based on the AS(T), a possible way to develop a real predictive equation of state is also suggested.

Growth of CdS crystals by the physical vapor transport method

Based on the physical vapor transport （PVT） method, the growth of large-size CdS crystals inside a vertical semi-closed tube is studied. Firstly, in order to ensure 1D diffusion-advection transport, multi-thin tubes are used in the growth tube. The XRD spectra of the CdS crystal grown in this configuration indicates that the crystal quality has clearly been improved, where the FWHM is 58.5 arcsec. Secondly, theoretical and experimental growth rates under different total pressures are compared; the results show that the experiential growth rate equation is valid for our semi-tube growth, and it could be used to estimate the growth rate and maximum growth time under different total pressures.

Behavior of Element Vaporization and Composition Control of Fe-Ga Alloy during Vacuum Smelting

Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.

Enhanced application for FSRU recondensing equipment during periods of low or no gas send out to minimize LNG cargo losses

Most modern floating storage and regasification units(FSRU)are fitted with recondensing equipment that feed condensed boil-off gas(BOG)to the regasification unit in addition to a stream of liquefied natural gas(LNG)extracted from the cargo tanks.Use of the recondenser during regasification operations reduces gas losses on FSRU.It does so by avoiding consumption of excess BOG,with no associated commercial benefit,in gas combustion units(GCU),steam dumps,flares etc.Here we consider the benefits of also using the recondenser in recirculation mode,returning condensed BOG to the cargo tanks in the form of slightly warmed LNG.Such recirculation can be beneficial during periods of low or no gas send out from the FSRU,often achieving significant reductions in gas losses,although it is not standard practice in the industry to do so.Once regasification is halted not much BOG is required by the FSRU engine room,so the vessel must handle this excess.By condensing the BOG to LNG and returning it to the cargo tanks,the significant volume reduction involved has the beneficial impact of slowing down tank pressure increase.The saturated vapor pressure(SVP)of the LNG,linked to its composition and temperature,plays a key role in the boil-off rate and resulting cargo tank pressure changes.Detailed analysis is provided to explain how using the FSRU recondenser in recirculation mode can be best exploited by considering the prevailing fill levels,temperatures and pressures in each of the cargo tanks,and returning the condensed LNG preferentially to certain tanks.FSRU efficiency can be improved,gas losses and emissions can be reduced,and more cargo sold by exploiting the capabilities of the FSRU recondenser in recirculation mode.Running the FSRU in recirculation mode requires no equipment modifications to standard recondensers,neither does it increase FSRU operating costs.