Li-rich layered oxides (LLOs) are considered as the promising cathode materials for next-generation high energy density lithium-ion batteries (LIBs). However, severe voltage fade and capacity decay hinder their commer...
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Based on selecting the proper formulas of thermal conductivity and viscosity for nanofluids, a three-dimensional fluid-solid conjugated model was developed to analyze the effect of the heat sink structure, the nanopar...
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Based on selecting the proper formulas of thermal conductivity and viscosity for nanofluids, a three-dimensional fluid-solid conjugated model was developed to analyze the effect of the heat sink structure, the nanoparticle kind, diameter and volume fraction, and the base fluid kind on the cooling performance of microchannel heat sink. The results showed that: (1) thermal dispersion effect caused by nanoparticle random motion enhanced the thermal convection of nanofluid thus enhances significantly the cooling performance of heat sink;(2) the enhancement of nanofluids was closely dependent on the heat sink structure and the dependence was distinct from the pure fluid, hence the heat sink structure was needed to be optimized for nanofluids as coolants;(3) as the nanoparticle volume fraction increases, the thermal resistance reduced and the pressure increased, the water-based Al2O3 nanofluid with 0.5% volume fraction was the optimal coolant which caused 10.1% decrease in the thermal resistance and only 0.38% increased in the pressure drop;(4) although the nanoparticle size had a small effect on the thermal resistance, nanoparticles with small diameter were recommended with consideration of stability of nanofluids;(5) Al2O3 nanoparticle was superior to TiO2 and CuO, and water was the better base fluid than ethylene glycol and engine oil.
The V-Cone flowmeter is a promising differential pressure flowmeter for metering the cryogenic fluid for its many advantages. When the cryogen velocity increases to a certain value, the cavitation may occur in flowmet...
The V-Cone flowmeter is a promising differential pressure flowmeter for metering the cryogenic fluid for its many advantages. When the cryogen velocity increases to a certain value, the cavitation may occur in flowmeter, which may significantly affect the performance of V-Cone flowmeter. However, the effect of cavitation on performance of V-Cone flowmeter remains unclear and there are no published studies to our knowledge on this issue. Here we investigate the performance of V-Cone flowmeter when measuring the cryogenic fluids, especially the effects of cavitation on the discharge coefficient and pressure loss coefficient of the flowmeter. Two cryogenic fluids are investigated, including liquid nitrogen (LN2) and liquid hydrogen (LH2). For comparison, the water is also investigated. The realizable κ-ε model is used to describe the turbulence. The Schnerr-Sauer cavitation model is used to investigate the effect of cavitation on the performance of the V-Cone flowmeter. The results show that there was little effect of cavitation on the discharge coefficient and pressure loss coefficient at the initial stage of cavitation. When the cloud cavitation occurred downstream of V-Cone, the discharge coefficient decreases rapidly with Reynolds number increasing, while the pressure loss coefficient rises quickly. The average discharge coefficient is almost the same for different fluids in the stable region; while the cryogenic fluids have wider stable Reynolds number ranges than the water. The lower limits of the Reynolds number for the constant discharge coefficient is very close for three fluids, however, for the upper limits of Reynolds number are quite different. We conclude that measurement range of the cryogenic fluid is much larger than that of the water, which shows that the V-Cone flowmeter exhibits great potential in the measurement of cryogenic fluid. This study provides insights into the effect of cavitation on the measurement of V-Cone flowmeter and opens a new aven
Bulk noble metal-semiconductor composites can be chosen as photocatalysts to carry out the continuous-flow (C-F) degradation of 4-nitrophenol (4-NP) whereas their preparation is complex and uncontrollable. Here, bulk ...
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In the cryogenic wind tunnel, cooling the circulating gas to cryogenic temperature by spraying liquid nitrogen (LN2) is an efficient way to increase the Reynolds number. The evaporation and motion of LN2 droplets in t...
In the cryogenic wind tunnel, cooling the circulating gas to cryogenic temperature by spraying liquid nitrogen (LN2) is an efficient way to increase the Reynolds number. The evaporation and motion of LN2 droplets in the high-speed gas flow is the critical process that determines the cooling rate, cooling capacity and the safe operation of the down-stream compressor. In this study, a numerical model of droplet motion and evaporation in high-speed gas flow is developed and verified against experimental data. The droplet evaporation rate, diameter and velocity are obtained during the evaporation process under different gas temperatures and flow velocities. The results show that the gas temperature has dominant influence on the droplet evaporation rate. High flow speed can increase droplet evaporation effectively at the beginning process. Evaporation of droplets with different diameters follows a similar trend. The absolute evaporation rate increases with the increase of droplet diameter while the relative evaporation amount is highest for the smallest droplet due to its high area-volume ratio. This numerical study provides insight for understanding the evaporation of LN2 droplets in high-speed gas flow and useful guidelines for the design of LN2 spray cooling.
Conventional carbon capture and storage technologies and carbon capture, utilization and storage technologies mainly target CO2 emissions from fixed sources, while direct air capture CO2 (DAC) technology, as an emergi...
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Conventional carbon capture and storage technologies and carbon capture, utilization and storage technologies mainly target CO2 emissions from fixed sources, while direct air capture CO2 (DAC) technology, as an emerging negative carbon emission technology, can capture CO2 emissions from distributed sources and further reduce the global atmospheric CO2 concentration. In this paper, the development process of DAC's typical liquid absorption process, solid adsorption process and the construction of relevant demonstration projects are introduced, the technical characteristics of emerging DAC processes are analyzed, and the key equipment schemes and future development trends of existing DAC processes are discussed. The DAC liquid absorption process has the characteristics of low cost of absorbent raw materials and high selectivity, which can realize a large-scale continuous capture, but high energy consumption in the regeneration process. The DAC solid adsorption process has the characteristics of modularity, low investment cost, and relatively low energy consumption in the regeneration process, but requires a regular replacement of adsorption materials and maintenance of adsorption equipment, which is suitable for small-scale DAC application scenarios. Two typical DAC process absorption/adsorption materials are reviewed. In the DAC electric oscillation adsorption process, CO2 is chemically captured in the solid electrode, and CO2 desorption is achieved by changing the polarity of the solid electrode with applied electric field. This process has a higher efficiency than that of the heat or pressure-based separation process. The CO2 in the air is selected through the DAC separation membrane to achieve an efficient carbon capture. The DAC process achieves the CO2 absorption and desorption through the change of humidity, which breaks through the high energy consumption limit of conventional variable temperature/pressure swing adsorption. The DAC bio-absorption process absor
Direct numerical simulations are performed to explore the effects of the rotating direction of the vertically asymmetric rough wall on the transport properties of Taylor-Couette (TC) flow, up to a Taylor number of Ta ...
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Photovoltaic–electrolysis (PV-EC) system currently exhibits the highest solar to hydrogen conversion efficiency (STH) among various technical routes. This perspective shifts the focus from the materials exploration i...
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Photovoltaic–electrolysis (PV-EC) system currently exhibits the highest solar to hydrogen conversion efficiency (STH) among various technical routes. This perspective shifts the focus from the materials exploration in photovoltaics and electrolysis to the critical aspect of thermal management in a PV-EC system. Initially, the theoretical basis that elucidates the relationships between temperature and the performance of both photovoltaics and electrolyzers are presented. Following that, the impact of thermal management on the performance of PV-EC for solar hydrogen production is experimentally demonstrated by designing variables-controlling experiments. It is observed that while utilizing identical PV and EC cells under varying thermal conditions, the highest STH can reach 22.20%, whilst the lowest is only 15.61%. This variation underscores the significance of thermal management in optimizing PV-EC systems. Finally, increased efforts to enhancing heat transfer and optimizing heat distribution are proposed, thus facilitating the design of more efficient PV-EC systems with minimized thermal energy losses.
The world's marine litter consists mainly of plastic, and 99% of it does not float on the surface of the sea but on the seabed. The plastic carbon footprint necessarily includes the extraction or manufacture of ra...
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The world's marine litter consists mainly of plastic, and 99% of it does not float on the surface of the sea but on the seabed. The plastic carbon footprint necessarily includes the extraction or manufacture of raw materials, the conversion process, the distribution of products, the consumption of specific types of products and the disposal of the final product, as all these stages release carbon into the atmosphere. This work, inspired by marine microplastics and investigates how plastic waste is degraded and transformed in high-pressure, low-temperature seawater, this paper investigates the corrosion of polyethylene terephthalate (PET) and polypropylene (PP) plastics in seawater at high-pressure, using artificial seawater temperatures to simulate ocean temperatures of approximately 4 °C and time settings of 1 day–7 days. The results show that increasing the time enhances the degradation of the plastics and that changing the pressure has little effect on the degradation effect. Understanding its degradation in seawater can help us to better treat plastic waste and thus reduce the carbon footprint of the disposal process.
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