The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and n...The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and numerical investigations have been conducted to explore supercritical water, carbon dioxide and R134a as heat transfer working fluids. Hydrofluoroolefin (HFO) and refrigerants blends have been considered the most environment-friendly refrigerants to replace Chlorofluorocarbons (CFCs), Hydrochlorofluoro-carbons (HCFCs) and Hydrofluorocarbons (HFCs). Their main advantage of zero Ozone Depletion Potential (ODP) and comparatively lower Global Warming Potential (GWP) have attracted growing amount of attention to mitigate environmental issues. This work adopts the computational method and takes the environmentally friendly refrigerants to investigate the heat transfer characteristics under widely used shear-stress transport (SST) model. A comprehensive comparison was performed at reduced pressure of 1.10 for supercritical fluids R515A, R1234ze(E) and R134a. The peaks of heat transfer coefficient occurred in the vicinity of pseudo critical temperature for all of these considered fluids;however, R134a resulted in higher heat transfer coefficient, Reynolds number and Prandtl number in comparison with R515A and R1234ze(E). The higher heat transfer coefficient of supercritical fluid R134a is owing to its thermophysical properties and the specific heat plays crucial role in the heat transfer of supercritical fluids. Owing to environmental issues, R515A can be a considerable replacement of R134a. R1234ze(E) is also promising alternative to R134a;however, safety issues should thoroughly concern its mild flammable characteristics.展开更多
The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial ...The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial for climate change. A </span><span style="font-family:Verdana;">considerable suggestion is R515A which possesses considerably lower global warming potential. The present simulations are designed to study supercritical fluid R515A under cooling conditions in horizontal position. The effect of pressure, mass flux, heat flux and tube diameter were considered for horizontal tube in the vicinity of pseudo critical temperature. Numeri</span><span style="font-family:Verdana;">cal investigations on heat transfer characteristics of supercritical fluid R515A were per</span><span style="font-family:Verdana;">formed using widely used shear-stress transport (SST) model. Moreover, heat transfer correlations </span><span style="font-family:Verdana;">were developed and suggested to accurately predict Nusselt number within 10% accuracy. </span><span style="font-family:Verdana;">The simulation results showed about 3.98% average absolute deviation.</span>展开更多
Drinking water disinfection is an essential process to assure public health all over the world.In this study,silver nanoparticles(AgNPs)on UiO-66(Zr)Metal-Organic Frameworks(Ag@UiO-66)is proposed as a potential water ...Drinking water disinfection is an essential process to assure public health all over the world.In this study,silver nanoparticles(AgNPs)on UiO-66(Zr)Metal-Organic Frameworks(Ag@UiO-66)is proposed as a potential water disinfection strategy.AgNPs are synthesized using polyvinyl pyrrolidone(PVP)as stabilizing agent,and sodium borohydride as reducing agent are subsequently embedded on UiO-66,a high-stability organometallic framework.The effect of premixing time,reaction time and reactant concentration on the loading rate of AgNPs on UiO-66 was investigated.The maximum load rate of AgNPs on UiO-66 could reach 13%when the premixing time is 3 h,the reaction time is 45 min and the concentration of AgNO_(3) is10μg/mL.The formation of AgNPs loaded on UiO-66 was observed and confirmed with ultraviolet and visible spectrophotometry(UV-Vis),scanning electron microscopy(SEM),infrared emission spectroscopy(IES)and X-ray diffraction(XRD)analysis.Ag@UiO-66 exhibited strong antibacterial activity against both Gramnegative Escherichia coli and Gram-positive Staphylococcus aureus,with minimum inhibitory concentrations(MIC)of 64 and 128μg/mL,respectively.The germicidal efficacy of Ag@UiO-66 enhanced significantly as the temperature rose from 4℃to 37℃.The results indicate that Ag@UiO-66 is potential candidate as a feasible water disinfection material.展开更多
With the large-scale integration of fracturing unit’s on-site construction,traditional industrial buses are increasingly unable to meet the requirements for the quantity transmission between various equipment in larg...With the large-scale integration of fracturing unit’s on-site construction,traditional industrial buses are increasingly unable to meet the requirements for the quantity transmission between various equipment in large-scale fracturing units,and different models of different equipment manufacturers cannot cooperate with each other as there are“Islands of information”in the control system.This article uses industrial Ethernet as the physical medium for data transmission.In addition,different equipment manufacturers use OPC as the core technology of the fracturing unit control system network,and set up an intelligent fracturing unit control system,so that the control network can quickly,accurately,and safely control the fracturing truck control system.The sand truck control system monitors and analyzes,saves,and prints the construction data in the vehicle instrument.At the same time,the network control system uses the vehicle instrument as the core of the network.It can control fracturing vehicles from different manufacturers.The sand mixer truck performs network control,which effectively avoids incompatibilities between various equipment manufacturers at the construction site.展开更多
The establishment of the Versailles System was marked with the Paris Peace Conference,which aimed to settle peace for World War I.The peace settlement was an excuse for the allied countries to regain and recover their...The establishment of the Versailles System was marked with the Paris Peace Conference,which aimed to settle peace for World War I.The peace settlement was an excuse for the allied countries to regain and recover their powers.This,in turn,called for large amount of reparations and punishments on the losing countries.The signing of the Treaty of Versailles heralded the collapse of the volatile system set up afterwards.Countries adopted the policies of appeasement,complied to the race of powers,and abandoned the so-called consensus on“peace”.Indeed,the collapse of the Versailles System had many causes.However,the rise of Nazi was its direct trigger.This article will mainly focus on how the Versailles System led to the rise of the Nazi and what the Nazi did to accelerate the fall of the system.展开更多
We demonstrate by theoretical analysis that periodically distributed viaduct piers of high-speed rail result in the Doppler effect in the seismic wavefield of high-speed rail at specific frequencies and analyze the Do...We demonstrate by theoretical analysis that periodically distributed viaduct piers of high-speed rail result in the Doppler effect in the seismic wavefield of high-speed rail at specific frequencies and analyze the Doppler effect’s influence on the wavefield’s spectrum feature.We further verify our theoretical prediction by using observational data of the high-speed rail seismic wavefield in Rongcheng,Hebei Province,China.We find that the wavefield component with a noticeable Doppler effect vibrates in the propagation direction and only has a unique apparent wave speed,indicating that P-wave is dominant.Furthermore,we propose a speed measurement method based on the Doppler effect and measure the wave speed of the medium along the rail.Measurement results are highly stable and consistent.展开更多
文摘The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and numerical investigations have been conducted to explore supercritical water, carbon dioxide and R134a as heat transfer working fluids. Hydrofluoroolefin (HFO) and refrigerants blends have been considered the most environment-friendly refrigerants to replace Chlorofluorocarbons (CFCs), Hydrochlorofluoro-carbons (HCFCs) and Hydrofluorocarbons (HFCs). Their main advantage of zero Ozone Depletion Potential (ODP) and comparatively lower Global Warming Potential (GWP) have attracted growing amount of attention to mitigate environmental issues. This work adopts the computational method and takes the environmentally friendly refrigerants to investigate the heat transfer characteristics under widely used shear-stress transport (SST) model. A comprehensive comparison was performed at reduced pressure of 1.10 for supercritical fluids R515A, R1234ze(E) and R134a. The peaks of heat transfer coefficient occurred in the vicinity of pseudo critical temperature for all of these considered fluids;however, R134a resulted in higher heat transfer coefficient, Reynolds number and Prandtl number in comparison with R515A and R1234ze(E). The higher heat transfer coefficient of supercritical fluid R134a is owing to its thermophysical properties and the specific heat plays crucial role in the heat transfer of supercritical fluids. Owing to environmental issues, R515A can be a considerable replacement of R134a. R1234ze(E) is also promising alternative to R134a;however, safety issues should thoroughly concern its mild flammable characteristics.
文摘The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial for climate change. A </span><span style="font-family:Verdana;">considerable suggestion is R515A which possesses considerably lower global warming potential. The present simulations are designed to study supercritical fluid R515A under cooling conditions in horizontal position. The effect of pressure, mass flux, heat flux and tube diameter were considered for horizontal tube in the vicinity of pseudo critical temperature. Numeri</span><span style="font-family:Verdana;">cal investigations on heat transfer characteristics of supercritical fluid R515A were per</span><span style="font-family:Verdana;">formed using widely used shear-stress transport (SST) model. Moreover, heat transfer correlations </span><span style="font-family:Verdana;">were developed and suggested to accurately predict Nusselt number within 10% accuracy. </span><span style="font-family:Verdana;">The simulation results showed about 3.98% average absolute deviation.</span>
基金supported by the Student Research Training Program(SRTP)of Zhejiang University[Y201931165]。
文摘Drinking water disinfection is an essential process to assure public health all over the world.In this study,silver nanoparticles(AgNPs)on UiO-66(Zr)Metal-Organic Frameworks(Ag@UiO-66)is proposed as a potential water disinfection strategy.AgNPs are synthesized using polyvinyl pyrrolidone(PVP)as stabilizing agent,and sodium borohydride as reducing agent are subsequently embedded on UiO-66,a high-stability organometallic framework.The effect of premixing time,reaction time and reactant concentration on the loading rate of AgNPs on UiO-66 was investigated.The maximum load rate of AgNPs on UiO-66 could reach 13%when the premixing time is 3 h,the reaction time is 45 min and the concentration of AgNO_(3) is10μg/mL.The formation of AgNPs loaded on UiO-66 was observed and confirmed with ultraviolet and visible spectrophotometry(UV-Vis),scanning electron microscopy(SEM),infrared emission spectroscopy(IES)and X-ray diffraction(XRD)analysis.Ag@UiO-66 exhibited strong antibacterial activity against both Gramnegative Escherichia coli and Gram-positive Staphylococcus aureus,with minimum inhibitory concentrations(MIC)of 64 and 128μg/mL,respectively.The germicidal efficacy of Ag@UiO-66 enhanced significantly as the temperature rose from 4℃to 37℃.The results indicate that Ag@UiO-66 is potential candidate as a feasible water disinfection material.
文摘With the large-scale integration of fracturing unit’s on-site construction,traditional industrial buses are increasingly unable to meet the requirements for the quantity transmission between various equipment in large-scale fracturing units,and different models of different equipment manufacturers cannot cooperate with each other as there are“Islands of information”in the control system.This article uses industrial Ethernet as the physical medium for data transmission.In addition,different equipment manufacturers use OPC as the core technology of the fracturing unit control system network,and set up an intelligent fracturing unit control system,so that the control network can quickly,accurately,and safely control the fracturing truck control system.The sand truck control system monitors and analyzes,saves,and prints the construction data in the vehicle instrument.At the same time,the network control system uses the vehicle instrument as the core of the network.It can control fracturing vehicles from different manufacturers.The sand mixer truck performs network control,which effectively avoids incompatibilities between various equipment manufacturers at the construction site.
文摘The establishment of the Versailles System was marked with the Paris Peace Conference,which aimed to settle peace for World War I.The peace settlement was an excuse for the allied countries to regain and recover their powers.This,in turn,called for large amount of reparations and punishments on the losing countries.The signing of the Treaty of Versailles heralded the collapse of the volatile system set up afterwards.Countries adopted the policies of appeasement,complied to the race of powers,and abandoned the so-called consensus on“peace”.Indeed,the collapse of the Versailles System had many causes.However,the rise of Nazi was its direct trigger.This article will mainly focus on how the Versailles System led to the rise of the Nazi and what the Nazi did to accelerate the fall of the system.
基金supported by the Spark Project for Earthquake Sciences and Technology in Hebei,China(Grant No.DZ20200827054)。
文摘We demonstrate by theoretical analysis that periodically distributed viaduct piers of high-speed rail result in the Doppler effect in the seismic wavefield of high-speed rail at specific frequencies and analyze the Doppler effect’s influence on the wavefield’s spectrum feature.We further verify our theoretical prediction by using observational data of the high-speed rail seismic wavefield in Rongcheng,Hebei Province,China.We find that the wavefield component with a noticeable Doppler effect vibrates in the propagation direction and only has a unique apparent wave speed,indicating that P-wave is dominant.Furthermore,we propose a speed measurement method based on the Doppler effect and measure the wave speed of the medium along the rail.Measurement results are highly stable and consistent.
