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 l...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.展开更多
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)ex...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.展开更多
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 p...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.展开更多
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...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.展开更多
基金financial support extended by the Beijing Natural Science Foundation (No.3192035)National Natural Science Foundation of China (No.51706068, NO.52376054)the Fundamental Research Funds for the Central Universities (No.2020MS034) is gratefully acknowledgement。
文摘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.
文摘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.
基金supported by the National Natural Science Foundation of China(21875278)Science and Technology Commission of Shanghai Municipality(20511107800).
文摘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.
文摘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.
