Recent interest in photocatalytic water splitting has intensified the demand in the development of photocatalysts capable of harnessing the full *** study introduces a novel WO_(x)/ZnIn_(2)S_(4)Zscheme heterojunction,...
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Recent interest in photocatalytic water splitting has intensified the demand in the development of photocatalysts capable of harnessing the full *** study introduces a novel WO_(x)/ZnIn_(2)S_(4)Zscheme heterojunction,prepared by depositing ZnIn_(2)S_(4)(ZIS)nanosheets onto WO_(x)nanorods,enabling efficient photothermal-coupled photocatalytic H_(2)*** success relies on the engineered oxygen vacancies within WO_(x)nanorods,which not only confer excellent photothermal properties lowering the reaction barrier but also create defect levels in WO_(x)facilitating Z-scheme electron transfer from these levels to the valence band of ***,the optimized WO_(x)/ZIS heterojunction exhibits a remarkable H_(2)evolution rate of 33.91 mmol h^(-1)g^(-1)with an apparent quantum efficiency of 23.6%at 400 *** study provides a new strategy for developing efficient Z-scheme heterojunctions with broadspectrum solar hydrogen production capabilities.
The supercritical carbon dioxide(sCO_(2))cycle can be powered by traditional as well as clean *** help users obtain more accurate results than the literatures with pre-set compressor efficiency,we proposed a complete ...
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The supercritical carbon dioxide(sCO_(2))cycle can be powered by traditional as well as clean *** help users obtain more accurate results than the literatures with pre-set compressor efficiency,we proposed a complete model to establish a link between the performance,sizes of compressors and parameters such as power W_(C),inlet temperature T_(in),inlet pressure P_(in)and pressure ratioε.Characteristic sizes of compressors l_(c),profile loss Y_(p)and clearance loss Ycl are all proportional to powers of W_(C)with powers of 0.5,-0.075 and-0.5 to 0 respectively;the scaling laws are constant in the range of capacities from 20 MW to 200 *** compressor isentropic efficiencyη_(tt)grows as the W_(C)increases,and the curves become *** efficiency improves over the full power range when the speed is changed from standard speed to the optimal speed;theη_(tt)curves turn soft as the n *** the P_(in)and T_(in)approach the critical point,theη_(tt)*** efficiency follows a parabolic curve as theεincreases,this parabolic distribution results from the tradeoff between the change in losses and the pressure distribution of ***η_(tt)versus P_(in),T_(in)andεrelations are similar at various capacities because of insignificant changes in the distribution of *** efficiency maps facilitate the estimation of system performance,while scaling law for irreversible losses and characteristic lengths,along with constant criterion analyses,aid in comprehending the characteristics of compressors across various capacities.
Spacecraft waste heat is dissipated into space primarily by radiation. To improve the heat dissipation efficiency of spacecraft radiators in high-temperature environments and reduce heat wastage in spaceflight thermal...
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The ability to unlock the interplay between the activity and stability of oxygen reduction reaction(ORR)represents an important endeavor toward creating robust ORR catalysts for efficient fuel ***,we report an effecti...
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The ability to unlock the interplay between the activity and stability of oxygen reduction reaction(ORR)represents an important endeavor toward creating robust ORR catalysts for efficient fuel ***,we report an effective strategy to concurrent enhance the activity and stability of ORR catalysts via constructing atomically dispersed Fe-Mn dualmetal sites on N-doped carbon(denoted(FeMn-DA)-N-C)for both anion-exchange membrane fuel cells(AEMFC)and proton exchange membrane fuel cells(PEMFC).The(FeMn-DA)-N-C catalysts possess ample dual-metal atoms consisting of adjacent Fe-N_(4)and Mn-N_(4)sites on the carbon surface,yielded via a facile doping-adsorption-pyrolysis *** introduction of Mn carries several advantageous attributes:increasing the number of active sites,effectively anchoring Fe due to effective electron transfer to Mn(revealed by X-ray absorption spectroscopy and density-functional theory(DFT),thus preventing the aggregation of Fe),and effectively circumventing the occurrence of Fenton reaction,thus reducing the consumption of ***(FeMn-DA)-N-C catalysts showcase half-wave potentials of 0.92 and 0.82 V in 0.1 M KOH and 0.1 M HClO_(4),respectively,as well as outstanding *** manifested by DFT calculations,the introduction of Mn affects the electronic structure of Fe,down-shifts the d-band Fe active center,accelerates the desorption of OH groups,and creates higher limiting *** AEMFC and PEMFC with(FeMn-DA)-N-C as the cathode catalyst display high power densities of 1060 and 746 mW cm^(-2),respectively,underscoring their promising potential for practical *** study highlights the robustness of designing Fe-containing dual-atom ORR catalysts to promote both activity and stability for energy conversion and storage materials and devices.
Hydrogen-based direct reduction of vanadium titanomagnetite is crucial for developing clean and efficient hydrogen metallurgy technology, while existing studies lack systematic research on the impact of H 2 /CO ratios...
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Hydrogen-based direct reduction of vanadium titanomagnetite is crucial for developing clean and efficient hydrogen metallurgy technology, while existing studies lack systematic research on the impact of H 2 /CO ratios on the reduction of vanadium titanomagnetite under non-isothermal conditions. This study examines the influence of varying H 2 /CO ratios on the non-isothermal reduction behavior and kinetics of vanadium titanomagnetite through thermogravimetric analysis (TGA). The results of thermogravimetric experiments show that raising the H 2 ratio can significantly lower the initial reduction temperature and accelerate the reduction rate. When H 2 /(H 2 +CO) rises from 0 to 1, the initial reduction temperature can be lowered by around 150 °C at a heating rate of 10 °C/min. As the heating rate decreases, the reduction curve shifts to the low-temperature region, and the reduction reaction becomes easier to proceed. The vanadium titanomagnetite reduction activation energy was calculated using the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) model-free kinetic methods, and the activation energy of vanadium titanomagnetite reduction under pure CO atmosphere (H 2 /(H 2 + CO) = 0) was the highest (120.74 kJ/mol by FWO and 107.82 kJ/mol by KAS). As the H 2 /(H 2 +CO) ratio increases, the activation energy continuously decreases, effectively reducing the reduction energy barrier of vanadium titanomagnetite. In contrast to an environment of pure CO, the activation energy for the reduction of vanadium titanomagnetite was reduced by 25.47 % (FWO method) or 28.73 % (KAS method) in a pure H 2 atmosphere (H 2 /(H 2 + CO) = 1), indicating that an elevated H 2 ratio significantly enhanced the reduction of vanadium titanomagnetite. XRD analysis showed that, after the non-isothermal reduction, unreduced iron oxide was still present within the vanadium titanomagnetite under a pure CO atmosphere, while the final reduction product was mainly metallic iron under differen
The air-Brayton cycle has the characteristics of safety and high efficiency, which can be used as an energy conversion system for mobile small reactors. The air turbine is one of the key components in the cycle system...
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The air-Brayton cycle has the characteristics of safety and high efficiency, which can be used as an energy conversion system for mobile small reactors. The air turbine is one of the key components in the cycle system, and improving its performance is of great significance. In this paper, an artificial neural network model combined with a genetic algorithm was used to optimize the rotor of an air centrifugal turbine with axial thrust and efficiency as the objective. The results show that the artificial neural network model can fit the CFD numerical simulation results well, with a coefficient of determination larger than 0.97. Then, after optimizing the artificial neural network model with a genetic algorithm, the total -total efficiency of the air centrifugal turbine was improved by 1.479 %, while the axial thrust was reduced by 1.07 %.
Refrigerant flash spray cooling, which offers high heat flux dissipation at low temperatures, holds significant potential for thermal management of high-power electronic devices. While surface structure design can fur...
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This study investigates the combustion characteristics of n-dodecane under pure oxygen conditions, a critical scenario for rocket propulsion systems. Advanced laser absorption diagnostics were employed to measure the ...
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Porous medium method is an effective simplified approach for the heat exchanger simulation when the numerous tubes and complex structures bring unacceptable computational resources to full-scale simulation. However, f...
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Porous medium method is an effective simplified approach for the heat exchanger simulation when the numerous tubes and complex structures bring unacceptable computational resources to full-scale simulation. However, for the specific C-shaped heat exchanger, the tube side resistance and flow distribution characteristics that significantly affects the heat transfer and natural circulation performance cannot be obtained by the traditional porous medium method coupled with the one-dimensional node model for tube side. It is urgent to develop a new coupling method that can not only simplify modeling and calculation, but also obtain tube side high-resolution flow heat transfer characteristics. This study presents a novel calculation method which couples the porous medium mesh and the tube side coarse mesh. The coupling method was then applied to a typical C-shaped passive residual heat removal heat exchanger (PRHR HX), which is significant to the stable operation and the mitigation of accident conditions in the nuclear power plant. The coupling calculation method was validated against the full-scaled simulation and data from scaled-down experiment. The average relative error of heat transfer power is 2.1 % under steady state conditions. Under transient conditions, the average absolute error of the fluid temperature and wall temperature are less than 6 K. Then the 3D thermal-hydraulic characteristics of PRHR HX was studied. Owing to a greater gravitational pressure head, the mass flow rates in the extended tubes surpass those in the shorter tubes by a relative deviation of 27.4 %. The upper horizontal tube's heat exchange capacity constitutes approximately 70 % of the total power, leading to enhanced natural circulation. The outlet temperatures from various tubes tend to equalize. The boiling area gradually extended down along the heat transfer tubes. Our work would present an innovative calculation method to the numerical study and design optimization of the C-shaped heat
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