Improving Heat Transfer in Parabolic Trough Solar Collectors by Magnetic Nanofluids

A parabolic trough solar collector(PTSC)converts solar radiation into thermal energy.However,low thermal efficiency of PTSC poses a hindrance to the deployment of solar thermal power plants.Thermal performance of PTSC is enhanced in this study by incorporating magnetic nanoparticles into the working fluid.The circular receiver pipe,with dimensions of 66 mm diameter,2 mm thickness,and 24 m length,is exposed to uniform temperature and velocity conditions.The working fluid,Therminol-66,is supplemented with Fe3O4 magnetic nanoparticles at concentrations ranging from 1%to 4%.The findings demonstrate that the inclusion of nanoparticles increases the convective heat transfer coefficient(HTC)of the PTSC,with higher nanoparticle volume fractions leading to greater heat transfer but increased pressure drop.The thermal enhancement factor(TEF)of the PTSC is positively affected by the volume fraction of nanoparticles,both with and without a magnetic field.Notably,the scenario with a 4%nanoparticle volume fraction and a magnetic field strength of 250 G exhibits the highest TEF,indicating superior thermal performance.These findings offer potential avenues for improving the efficiency of PTSCs in solar thermal plants by introducing magnetic nanoparticles into the working fluid.

Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators

Zinc ion hybrid capacitors(ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applications. Carbon-based materials are deemed the competitive candidates for cathodes of ZIHC due to their cost-effectiveness, high electronic conductivity, chemical inertness, controllable surface states, and tunable pore architectures. In recent years, great research efforts have been devoted to further improving the energy density and cycling stability of ZIHCs. Reasonable modification and optimization of carbon-based materials offer a remedy for these challenges. In this review, the structural design, and electrochemical properties of carbon-based cathode materials with different dimensions, as well as the selection of compatible, robust current collectors and separators for ZIHCs are discussed. The challenges and prospects of ZIHCs are showcased to guide the innovative development of carbon-based cathode materials and the development of novel ZIHCs.

Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High‑Performance Zinc Anode:Principles,Strategies,and Challenges

The last several years have witnessed the prosperous development of zinc-ion batteries(ZIBs),which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety.However,the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth,hydrogen evolution,and corrosion passivation on anode side.A functionally and structurally well-designed anode current collectors(CCs)is believed as a viable solution for those problems,with a lack of summarization according to its working mechanisms.Herein,this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs,which can be divided into zincophilic modification,structural design,and steering the preferred crystal facet orientation.The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

A pre-strain strategy of current collectors for suppressing electrode debonding in lithium-ion batteries

The interfacial debonding between the active layer and the current collector has been recognized as a critical mechanism for battery fading,and thus has attracted great efforts focused on the related analyses.However,much still remains to be studied regarding practical methods for suppressing electrode debonding,especially from the perspective of mechanics.In this paper,a pre-strain strategy of current collectors to alleviate electrode debonding is proposed.An analytical model for a symmetric electrode with a deformable and limited-thickness current collector is developed to analyze the debonding behavior involving both a pre-strain of the current collector and an eigen-strain of the active layers.The results reveal that the well-designed pre-strain can significantly delay the debonding onset(by up to 100%)and considerably reduce the debonding size.The critical values of the pre-strain are identified,and the pre-strain design principles are also provided.Based on these findings,this work sheds light on the mechanical design to suppress electrode degradation.

Stress Path Analysis of Deep-Sea Sediments Under the Compression-Shear Coupling Load of Crawler Collectors

The mechanical properties of deep-sea sediments during the driving process of crawler collectors are essential factors in the design of mining systems.In this study,a crawler load is divided into a normal compression load and a horizontal shear load.Then,the internal stress state of sedimentary soil is examined through a theoretical calculation and finite element numerical simulation.Finally,the driving of crawlers is simulated by changing the relative spatial position between the load and stress unit,obtaining the stress path of the soil unit.Based on the calculation results,the effect of the horizontal shear load on the soil stress response is analyzed at different depths,and the spatial variation law of the soil stress path is examined.The results demonstrate that the horizontal shear load has a significant effect on the rotation of the principal stress,and the reverse rotation of the principal stress axis becomes obvious with the increase in the burial depth.The stress path curve of the soil is different at various depths.The spatial variation rule of the stress path of the shallow soil is complex,whereas the stress path curve of the deep soil tends to shrink as the depth increases.The stress path of the corresponding depth should be selected according to the actual research purpose and applied to the laboratory test.

Surface-roughened current collectors for anode-free all-solid-state batteries

Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss.Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.

Interactive Effect of Copper and Its Mineral Collectors on Soil Microbial Activity—A Microcalorimetric Analysis

Discharge of metals and their mineral flotation collectors into the soil environment causes severe ecological and health impacts, which is still not fully understood. This is of great concern, particularly with regards to their effect on the soil microorganisms whose functions determine not only the soil quality and function but also influence the air and water quality. This study aimed to analyze and compare, microcalorimetrically, the single chemical toxic effect with the combined effect of copper (Cu) and two of its main flotation collectors, potassium amyl xanthate (PAX) and sodium isoamyl xanthate (SIAX), on soil microbial community. All chemicals, individually and as a binary mixture of copper and each of its flotation collectors, exhibited a significant dose-effect relationship, and the highest and lowest microbial activity inhibition being associated with SIAX and Cu, respectively (e.g. IC 50 of 447.5, 158.3 and 83.9 μg·g?1 soil for copper, PAX and SIAX, respectively). For all cases, the microbial activity was more affected by the mixture than by the individual mixture components. Increasing the xanthates dose (from 25 to 100 μg·g?1 soil) in the mixture with a copper dose of 200 μg·g?1 soil led to the increase of the microbial activity inhibition rate, from 23.08 % to 53.85% in case of PAX and from 26.92% to 57.69% in case of SIAX). Similarly, the toxicity level of the mixture of equitoxic components doses increased with the increased mixture doses. Since the observed activity level can be attributed to the surviving microbes, capable of adapting to both chemical and their mixture, a genetically based analysis should be conducted to allow identifying and characterizing the potentially resistant strains that can be useful for the remediation of the pollution by copper and xanthates and for the sustainability of copper mining and flotation, and for all soil, water, and air quality and function interest.

STUDY ON MECHANISM OF MIXED COLLECTORS IN SEPARATION OF FELDSPAR AND QUARTZ

Acidless and fluoless flotation is a new method for sepa-rating feldspar from quartz at the natural pH value of tap water in the ab-sence of any acid and fluoride and other inorganic reagents.The paperdiscusses the mechanism of mixed collectors in separation of feldspar andquartz by means of mono-mineral flotation experiment,determination ofsurface-tension,analisis of fluorescence,infrared spectrum,Auger electron sepectrum,and quantum chemistry calculation.

Study on Selection of Dust Collectors for Large Capacity Thermal Power Units in High Altitude Areas

A dust collector is an important equipment in a thermal power plant,and reasonable selection of a dust collector is important for environmental protection in the power plant. Huaneng Xining Power Plant is located at an elevation of 2 360 m. Based on the characteristics of the high altitude area and their special requirements for dust collectors,the selection of dust collectors for the thermal power unit in the high altitude area was studied,and then two types of dust collectors( a rotary electrode electrostatic precipitator and electric-bag composite precipitator) for the thermal power unit were compared from the aspects of technological and economical feasibility. Finally,a proposal to select a suitable dust collector for the thermal power plant was put forward.

Proposal of a Solar Thermal Power Plant at Low Temperature Using Solar Thermal Collectors

To this day, only two types of solar power plants have been proposed and built: high temperature thermal solar one and photovoltaic one. It is here proposed a new type of solar thermal plant using glass-top flat surface solar collectors, so working at low temperature (i.e., below 100°C). This power plant is aimed at warm countries, i.e., the ones mainly located between -40° and 40° latitude, having available space along their coast. This land based plant, to install on the seashore, is technologically similar to the one used for OTEC (Ocean Thermal Energy Conversion). This plant, apart from supplying electricity with a much better thermodynamic efficiency than OTEC plants, has the main advantage of providing desalinated water for drinking and irrigation. This plant is designed to generate electricity (and desalinated water) night and day and all year round, by means of hot water storage, with just a variation of the power delivered depending on the season.

Ponceau 2R Doped Poly (ST/MMA) as Fluorescent Solar Collectors and Evaluation Effect of Matrix on Their Field Performance

Luminescent solar concentrators (LSCs) with styrene (ST) and methylmethacrylate (MMA) of different percentage as the matrix were prepared by a casting method using ponceau 2R. DSC has been used to compare the thermal stability of the different LSCs. FTIR spectroscopy shows that appearance of -N=N- for ponceau 2R in all ST/MMA matrixes indicating that the highest stability of this kind of dye in these matrixes. The values of the optical band gap (Eg) have been obtained from direct allowed transition before and after the samples have been exposed to sunlight for 9 weeks. Photodegradation studies revealed that the more photostable dye doped in PMMA matrix than in other matrixes. The results showed that the homo PMMA/ponceau 2R system has the highest fluorescence quantum yield (Qf). Therefore this sample can be selected for field performance of fluorescent solar collectors. The photovoltaic cell coupled with homo PMMA/2R LSC shows a maximum efficiency, 2% compared to the normal one.

Solar Thermal Systems Performances versus Flat Plate Solar Collectors Connected in Series

This paper shows the modeling of a solar collective heating system in order to predict the system performances. Two systems are proposed: 1) the first, Solar Direct Hot Water, which is composed of flat plate collectors and thermal storage tank, 2) the second, a Solar Indirect Hot Water in which we added an external heat exchanger of constant effectiveness to the first system. The mass flow rate by a collector is fixed to 0.04 Kg·s–1 and the total number of collectors is adjusted to 60. For the first system, the maximum average water temperature within the tank in a typical day in summer and annual performances are calculated by varying the number of collectors connected in series. For the second, this paper shows the detailed analysis of water temperature within the storage and annual performances by varying the mass flow rate on the cold side of the heat exchanger and the number of collectors in series on the hot side. It is shown that the stratification within the storage is strongly influenced by mass flow rate and the connections between collectors. It is also demonstrated that the number of collectors that can be connected in series is limited. The optimization of the mass flow rate on cold side of the heat exchanger is seen to be an important factor for the energy saving.

Electronic Money Collectors

As many kinds of shops boostedin China in 1995,domestic andoverseas manufacturers anddistributors of all kinds of moneycollectors witnessed a good marketin China.In 1995,the sales volumeof money collectors was 30,000,anannual growth rate of 30 percent.The money collectors that canmanage money and key commoditymanagement account for two fifthsof total sales volume,the moneycollectors that can manage moneyand single commodity managementwith multifunctions andtelecommunication capacity of ECRPOS and the POS of PC-BASErespectively,for one third.

Skin diseases in tea collectors

The tea collection is a difficult and laborious task, but few studies have analyzed risks by work activities or the work environment. To investigate the effects of work activities and work environment on tea collectors by looking from dermatological perspective, detailed dermatological examination was performed on tea collectors and clinical backgrounds of the participants were questioned and all findings were noted. The participants clinically suspected for skin, hair and nail infections have been referred to our hospital microbiology laboratory for sampling. The most common diseases in the participants were allergic contact dermatitis, irritant contact dermatitis and acute paronychia. These three diseases accounted for 59.1% of the total diseases in tea collectors. Clinical background story was unremarkable in the vast majority of participants. The current study draws attention to this business area and health problems of tea collectors. The authors think that, use of protective equipment such as masks and gloves during working and receiving of safety training related to their job will decrease work-related health problems of tea collectors.

Effect of N-substituents on performance of thiourea collectors by density functional theory calculations

Using density functional methods,some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges,which are related to the reactive behavior of thioureas containing different N-substituent groupings.The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors.The order of electron-donating ability is N-propyl-N'-benzyl-thiourea(PBZYTU)>N-propyl-N'-ethyl-thiourea (PETU)>N-propyl-N'-allyl-thiourea(PALTU)>>N-propyl-N'-acetyl-thiourea(PACTU)>N-propyl-N'-ethoxycarbonyl-thiourea (PECTU)>N-propyl-N'-benzoyl-thiourea(PBZOYTU),and the order of feedback-electron-accepting ability is PBZOYTU> PACTU>PECTU>>PALTU>PETU>PBZYTU.This implies that PBZOYTU,PACTU or PECTU can react with copper atoms having(t2g) 6 (eg) 3Cu(II)or t 6e 4Cu(I)configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond,and exhibit excellently collecting performance for copper sulfide minerals.These are consistent with the experimental data reported in the literatures.

Preliminary examination of electrochemical and spectroscopic features of trithiocarbonate collectors for sulfide mineral flotation

The redox potentials of xanthate/dixanthogen (dithiocarbonate/di dithiocarbonate, DTC/(DTC) 2) and trithiocarbonate/di trithiocarbonate (TTC/(TTC) 2) couples have been measured for the potassium salts. The spectroscopic characteristics of these sulfide mineral collectors were determined by FTIR and UV analysis. Electrochemically controlled contact angle measurements at a pyrite surface provided the basis to analyze the effect of the functional group ( O CS 2 versus S CS 2) on the hydrophobic surface state. Results from this preliminary examination are discussed with respect to the nature of collector adsorption and the pyrite flotation response.

An in situ ATR-FTIR study of mixed collectors BHA/DDA adsorption in ilmenite-titanaugite flotation system

This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine(BHA/DDA).The interface assembly mechanism was mainly investigated through in situ attenuated total reflectance Fourier transform infrared(ATRFTIR)spectroscopy combined with the two-dimensional correlation spectroscopy(2D-COS)and X-ray photoelectron spectroscopy(XPS).It has been found that BHA/DDA mixed collectors successfully separate ilmenite from titanaugite at a molar ratio of 8:1.Zeta potential experiments suggested that,in the presence of mixed collector system,the BHA-DDA complex adsorbed on the ilmenite surface via the chemically adsorbed BHA and the electrostatically adsorbed DDA,however,the complex adsorbed on the surface of titanaugite unstably.According to in situ ATR-FTIR combined with 2D-COS and XPS results,the interface assembly mechanism of BHA/DDA is summarized as:the function group of BHA molecules first binds to the metal sites on minerals to form bidentate ligand,then DDA co-adsorbed with BHA on the surface of minerals through hydrogen bonding.DDA may change the adsorption modes of some BHA on the ilmenite surface from four-membered ring to five-membered ring,while the modes on the titanaugite surface is true opposite.Finally,recommended adsorption configurations of the BHA/DDA complex on the two mineral surfaces are proposed.

Heat Transfer Optimization in Air Flat Plate Solar Collectors Integrated with Baffles

This paper presents an experimental analysis for comparisons of conventional flat plate solar collectors and collectors integrated with different numbers of baffles. Heat transfer between absorber plate and drying fluid (air) has been one of the major challenges in the design and operations of the indirect solar dryer systems. In this experiment, efficiency of air flat plate solar collector integrated with 2, 3, 4 and 8 baffles was studied and compared with the ordinary collector. The results showed that integrating solar collector with baffles significantly increased the efficiency of the system. It was noted that collector with 2, 3, 4 and 8 baffles had a mean efficiency of 29.2%, 31.3%, 33.1% and 33.7% respectively while with no baffles was 28.9%. The analysis showed that when there were less than four baffles in the collector, heat transfer was dominant over pressure drop and hence high efficiency. However, when the number of baffles exceeded four, the effect associated with an increase in pressure drop highly observed compared to heat transfer coefficient, thus resulted to insignificant increase in efficiency. Therefore, the optimum number of four baffles was commended for the designed model for optimum efficiency.

Contribution to the understanding of the performance differences between commercial current collectors in Li–S batteries

Lithium–sulfur batteries have been recognised as highly promising next-generation batteries, due to their low cost and high theoretical energy density. Despite numerous advances in this technology over the last decade, its commercialisation is still a challenge that has not yet been achieved. Many efforts have been made to improve the problems that these batteries present, mainly by investigating different cathode manufacturing strategies, testing novel Li anodes, new additives in the electrolytes, and modified separators or interlayers. However, the characteristics of the current collectors used in the preparation of the electrodes have been rarely addressed. Three commercial collectors are commonly used in basic research on Li–S batteries: Al foil, carbon coated Al foil (Al-C), and carbon paper (gas diffusion layer, GDL). In this work, a detailed study of the electrochemical response of these commercial collectors has been carried out. The tests were carried out on two S composites formed by carbons of a different natures, commercial carbon black and synthetic N-doped graphene. In addition, the S impregnation method was different, using either melt diffusion at 155 ℃ or ethylenediamine as S solvent, respectively. In both systems, the results were similar – the electrodes supported on GDL delivered higher specific capacities than those supported on Al and Al-C, with minimal differences between the two. Of the different collector properties examined to explain this behaviour, namely Al corrosion, electrical conductivities, surface-level composition, and surface texture, only the latter had a significant effect in the performance of GDL-based electrodes. SEM images revealed a rough and cracked surface formed by the agglomerated carbon particles that give rise to a complex pore system, predominantly consisting of macropores. All of these features are beneficial for a better anchoring of the active material on the collector surface, in addition to enhancing the wettability of the electrolyte and favouring reaction kinetics. In contrast, the Al-based collector possesses a very smooth and non-porous surface, detrimental to both the active material-substrate interface and the active material impregnation by the electrolyte.

Stromatolites are the Potential Collectors of Oil and Gas

Stromatolite buildups are spread throughout the Earth and are known in sediments of different age. First stromatolite buildups were investigated in Shark-Bay in Western Australia.Their age is valued as 3.5 billion years,the same age of first living organisms on the Earth.Stromatolites are