Increasing Working Temperature Research Articles

Attenuated Natural Convection in Molten Salt Electrochemical Systems with Minimal Heat Dissipation.

The accurate understanding of mass transfer in molten salt contributes to revealing the reaction mechanism and advancing the technologies. The existence of notable natural convection effects has been demonstrated in our previous studies, even though the driving forces for such a high natural convection are still not clear. Herein, we showed that the intense natural convection in molten salts resulted from severe heat dissipation through the electrodes (or the system). With an adiabatic design, natural convection effects were significantly suppressed in molten LiCl-KCl. The derived value of the natural convection layer (δconv) ranged from 190 to 250 μm in molten LiCl-KCl containing a redox couple (e.g., SmCl3, EuCl3, and CrCl3), comparable to those in aqueous solutions. The values of δconv in LiCl-KCl-173 mM CrCl3 increased to ∼360 μm due to the change in salt viscosity. The density-driven convection became dominant under a high redox concentration, and the increasing working temperature had no apparent effect on the natural convection effects because of the adiabatic design.

Cent-Hydro: A Novel Temperature and Pressure-Controlled Hybrid System for Large-Scale Nanofiber Production

The present study aimed to develop a novel temperature and pressure-controlled hybrid system (Cent-Hydro) for large-scale nanofiber production. Nanofibers from a hydrophilic carrier matrix were prepared using the Cent-Hydro system. This study explores the effect of increasing working temperature on the surface tension and viscosity of polymer solutions. The Cent-Hydro system was calibrated through the process of jet formation, and spinning parameters were identified for the jet path. The formation of fingers in front of the thin liquid occurred due to Rayleigh–Taylor instability, and a lower concentration of polymer solution favoured the development of thinner and longer fingers. The critical angular velocity and initial velocity for jet formation were obtained when the balance between surface tension, centrifugal force, and viscous force was achieved. The effect of increasing rotational speed and working temperature on finger velocity and length was experimentally evaluated, concluding that an increase in working temperature increases finger velocity and length. Additionally, the effect of increasing rotational speed, polymer concentration, and working temperature on the diameter of the nanofiber was evaluated. Overall, the Cent-Hydro system presents a compelling proposition for large-scale nanofiber production, offering distinct advantages over conventional methods and paving the way for advancements in various applications.

Hollow mesoporous In2O3 derived from MIL-68 (In) for dual gas sensing of NO2 and H2

NO2 is one of the most important air pollutant gases for the environment and human health. H2 is seen as the next generation of clean energy to promote sustainable development. However, sensitive detection of NO2 at room temperature is still a major challenge, and reliable H2 sensors are also scarce. Metal oxide semiconductor (MOS) gas sensors are advantageous for detecting gas. Hence, we synthesized the unique hexahedral hollow mesoporous In2O3 (h-In2O3) derived from MIL-68 (In). The formation process and properties of h-In2O3 were analyzed. The surface of h-In2O3 is rich in hydroxyl groups, which are active sites for NO2 adsorption at room temperature. Increasing working temperature up to 160 °C enables effective sensing reaction with H2. Based on different temperature-dependent gas sensing mechanisms, the h-In2O3 sensor exhibits ultrasensitive response values of 400 towards 100 ppb NO2 at room temperature (24 °C) and of 17.99 towards 10 ppm H2 at 160 °C. In addition, the h-In2O3 sensor exhibits reliable linear response, low theoretical detection limit of 1.8 ppt and 23 ppb for NO2 and H2, excellent selectivity, repeatability and long-term stability. The synergistic effect of the unique structure, larger specific surface area, and abundant adsorbed oxygen plus oxygen vacancy contribute to the excellent gas sensing performance of the h-In2O3 sensor. This study provides a promising strategy for the development of bifunctional gas sensors.

High-temperature magnetic performance and corrosion resistance of hot-deformed and sintered Nd-Fe-B magnets with similar room-temperature magnetic properties

Both hot-deformed (HD) and sintered Nd-Fe-B magnet have huge prospect in the application of permanent magnet servomotor, but its magnetic performance is often influenced by increased working temperature and corrosion environment. Hereby, the high-temperature magnetic performance and corrosion resistance of HD magnets and sintered magnets with similar room-temperature magnetic properties were investigated. The melt-spun Nd-Fe-B powders of MQU-F and MQU-G have been used to prepare the HD magnets without (HDF) and with (HDG) heavy rare earth of Dy element. The sintered magnets of 45H grade (S45H) and 35UH grade (S35UH) were used as reference magnets to evaluate the high-temperature magnetic performance and corrosion resistance of HDF and HDG, respectively. The results show that both HDF and HDG have superior temperature coefficient of coercivity (β), irreversible flux loss (hirr) and corrosion resistance to the same-grade sintered magnets. The analysis on microstructure and element composition reveals that the difference in β and hirr between HD and sintered magnets is mainly resulted from grain size and Pr content. The nanograins in HD magnets are much smaller than the micrograins in sintered magnets. Consequently, |β| and hirr reduces significantly with the decrease of grain size. Meanwhile, the Pr-contained sintered magnets of S45H and S35UH consist of both Pr2Fe14B and Nd2Fe14B phases. As the magneto-crystalline anisotropy of Pr2Fe14B decreases faster than that of Nd2Fe14B with the increased temperature. |β| and hirr of the HDF and HDG are better than those of the same-grade sintered magnets. In addition, the difference in corrosion resistance is primarily caused by the grain boundary (GB) width, the total rare earth (TRE) content and Co content. The corrosion on Nd-Fe-B magnet initiates from and propagates along GB and the boundary of flake particles at the surface of HD and sintered magnets. The narrower GB width, lower TRE content and higher Dy content all play important role in better corrosion resistance of HD magnets.

A Review of Radiative Heat Transfer in Fixed-Bed Particle Solar Receivers

A highly efficient receiver is required because re-radiation loss increases dramatically with increased working temperature. Among a large number of receivers, the fixed-bed Particle Solar Receiver (PSR) represents a new pathway to high temperature with maximum overall thermal efficiency. The incoming solar radiation can penetrate deeper into the fixed-bed PSR filled with semi-transparent quartz and ceramic particles (spheres or Raschig rings), resulting in an increased volumetric effect. Reports show that an optimized PSR can realize overall receiver efficiency of around 92% at outlet temperatures above 1000 K, and achieve the annual temperature above 1000 K over 65% annual operating hours integrated with a concentrated solar power (CSP) system. To fully understand radiative heat transfer characteristics and provide deep insight into thermal efficiency, radiation energy is classified as incident solar radiation and radiative heat exchange in two parts. The transfer mechanism, the solution method and the progress of the investigation for each section are summarized and discussed in detail. Then, challenges and future directions, including an innovative design method, an improved experimental approach and an effective simulation method are proposed to put forward this receiver to be a preferred substitute in advanced, high-temperature power cycles.

Production of small peptides and low molecular weight amino acids by subcritical water from fish meal: Effect of pressurization agent

The hydrolysis of the water-soluble protein (WSP) fraction from tuna fish meal was evaluated by subcritical water (subW) by using N2 and CO2 as different pressurization agents in the temperature range from 140 to 180 °C. For both gases, the amino group release increased by increasing working temperature while the Lowry response decreased due to production of smaller-size peptides and free amino acids.The free amino acid content was higher with CO2 than with N2. At 180 °C, 344 ± 5 and 275 ± 3 mg of free amino acids per g of WSP were released, respectively; although, in both systems the smallest molecular weight amino acids, glycine and alanine, were preferentially released. The free amino acids content obtained by enzymatic hydrolysis with commercial proteases Alcalase and Novozym was much lower with the highest hydrolysis yield determined for histidine. These results have been supported by size exclusion chromatography analysis.

Application of Heat-Enhancement for Improving the Sensitivity of Quartz Crystal Microbalance.

The use of quartz crystal microbalance in trace mass detection is restricted by unsatisfactory sensitivity, especially in damping media, due to the worsening of the quality factor of the damping resonator. The enhancement of the sensor performance could be realized by increasing the innate resonant frequency of quartz oscillators. Herein, increased working temperature of QCM systems was proved to bring an enhancement of the original resonant frequency. In addition, the measurement of ion osmotic pressure, single layer formation and single nucleotide polymorphism (SNP) at different temperatures demonstrated that an increased working temperature could enhance the sensitivity and accuracy, suggesting a potential application in a series of trace detections.

Greatly Enhanced Methanol Oxidation Reaction of CoPt Truncated Octahedral Nanoparticles by External Magnetic Fields

Tunable behavior in electrocatalysis by external multifields, such as magnetic field, thermal field, and electric field, is the most promising strategy to expand the theory, design, and synthesis of state‐of‐the‐art catalysts and the cell in the near future. Here, a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions (MOR) in magnetic nanoparticles is reported. For Co42Pt58 truncated octahedral nanoparticles (TONPs), the catalytic performance in MOR is greatly increased to the maximum of 14.1% by applying a magnetic field up to 3000 Oe, and it shows a monotonical increase with increasing working temperature. The magnetic enhanced effect is closely related to the Co content of CoxPt100‐x TONPs. Furthermore, the enhancement effect under a magnetic field is more obvious for Co42Pt58 TONPs annealed at 650 °C. First‐principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier, where OHad intermediates on Co sites play a more important role. The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells, which will accelerate their potential applications.

Synergistic integration of molten hydroxide direct carbon fuel cell and Stirling heat engine for efficient and clean coal use

To reuse the exhaust heat produced by molten hydroxide direct carbon fuel cells (MHDCFCs), a new combined system mainly composed of an MHDCFC, a regenerator, and a Stirling heat engine (SHE) is theoretically integrated for fuel-to-power efficiency enhancement. Mathematical formulas of the performance indicators for the combined system are derived based on the first and second laws of thermodynamics, from which the feasibility and effectiveness of the combined system are evaluated from both energetic and exergetic viewpoints. Moreover, the optimum working regions of the combined system are further specified by using a multi-objective function paying equal attention to both efficiency and power output. Results show that SHEs can be effectively acted as bottoming cycles for MHDCFC for additional mechanical power production. Numerical calculations indicate that the maximum power density and its corresponding energy efficiency and exergy efficiency of the proposed system are, respectively, about 97.6%, 97.1% and 99.2% greater than that of the single MHDCFC. Furthermore, extensive parametric studies show that increasing working temperature, volume ratio, hot-side working substance temperature or mean pressure is beneficial for the overall system performance, while increasing reactor compartment width may degrade the overall system performance.

34‐2: Invited Paper: Analysis of Temperature Effect of RGB Mini/Micro LED Chips

Mini/Micro light‐emitting‐diode (LED) emissive display has attracted wide range of attentions and has a good development prospect. One of the big challenges of Mini/Micro LED display is that the attenuation degree of luminous intensity of RGB chips with increasing working temperatures are different. In this work, we deeply analyzed this phenomenon and found out the factors contributing to that. It is found out that the attenuation degree of luminous intensity is directly related to the current density and material system of the chips. Moreover, the defect related non‐radiative recombination process and the different band structures between AlGaInP system and InGaN system are regarded as the main factors contributing to the different attenuation degree of luminous intensity with increasing working temperature of RGB chips.

The Effects of Damage to the Outer Race Bearing on the Efficiency of the Induction Motor Using Fast Fourier Transform (FFT) Method

Bearing is an induction motor component that helps the rotor to move freely, in industrial applications it is important to maintain bearing performance in induction motors. In its use, bearing damage is one of the biggest types of damage that is often found in induction motors. Bearing damage can lead to increased vibration, increased noise, increased working temperature, and decreased efficiency. Efficiency reduction can be used as information on the condition of the motor so that this information can be used to detect damage before more serious damage occurs. This research discusses the stator current analysis method and the efficiency of damage to the motor through two harmonic amplitude ratios equipped with the fast Fourier transform (FFT) algorithm in detecting damage to the outer race bearing. It is hoped that this efficiency can be used as an evaluation of the extent to which motor energy waste occurs before more severe damage. The efficiency results on the damage to the outer race bearing using the FFT method get the highest efficiency value of 1.47 and the lowest value of 0.66.

Corrosion of Metallic Materials in 3LiCl-2KCl and 3LiCl-2KCl-UCl3

High-temperature molten salts are widely used in production and refining of non-ferrous and rare metals, in nuclear technology and solar storage systems. However, application of such technologies is limited by the problem of finding suitable corrosion resistant materials capable of withstanding a prolonged contact with molten salts.Current study is focused on the corrosion of metallic materials in 3LiCl-2KCl-based melts.Metallic tantalum and molybdenum, nickel-chromium-molybdenum alloys (VDM Alloy C-4, Hastelloy G-35 and specially designed KhN62M alloy) were chosen as the objects of the investigation. Corrosion tests were performed in 3LiCl-2KCl and 3LiCl-2KCl-UCl3 (5 wt. % U) melts. The corrosion tests run for 100 h, and the temperature was varied from 450 to 750 °C. The corrosion rates were determined by both gravimetric technique and chemical analysis of quenched melts. The last technique is very useful in case of alloys formation on the surface of tested samples.It was found that all the above metallic materials can be used in 3LiCl-2KCl melts at 450 and 550 °C. Increasing working temperature led to intensification of corrosion processes. This effect was more pronounced for nickel-based alloys where increasing temperature to 650 °C also resulted in changing character of the corrosion. The undesirable intergranuluar corrosion was noticed for the nickel-based alloys at 750 °C and this was induced by the formation of secondary phases at the grain boundaries.Metallic tantalum and molybdenum were subjected to only gradual etching even at 750 °C. Their corrosion rates did not exceed 0.01 mm/year and these materials can be recommended for the application in contact with molten chlorides at 750 °C.Addition of uranium(III) chloride to the melt led to increasing corrosion rate for all the materials studied. The corrosion mechanism, however, did not change much with temperature. The presence of oxidant (U3+) resulted in acceleration of corrosion etching. The rate of the exchange reaction between uranium chlorides and components of the materials can be accelerated by the formation of U-Ni alloys. Formation of metallic uranium-containing layers on the surface of nickel-based samples deserves a separate attention as an element of possible currentless protection coatings.The corrosion resistance of tantalum and molybdenum is also sufficient at 750 °C in 3LiCl-2KCl-UCl3 (5 wt. % U). However, it should be remembered that their mechanical properties, weldability, and high-temperature resistance in air are noticeably worse compare to the nickel-based alloys.

Effect of working temperature on the interfacial behavior of overmolded hybrid fiber reinforced polypropylene composites

In the present study, the interfacial behavior of overmolded hybrid fiber reinforced polypropylene composites (hybrid composites) in the working temperature range from 23 °C to 90 °C was studied by experimental and constitutive methods. Monotonic and cycle loading-unloading single-lap-shear tests were employed to determine the interfacial properties of hybrid composites. The experimental results show that both interfacial shear strength and shear stiffness decrease with increasing working temperature. A regression function was adopted to evaluate the decaying degree of interfacial properties with increasing working temperature. The shear stress-displacement relationship under monotonic loading exhibits nonlinear behavior after an initial elastic region. The envelope lines of shear stress-displacement of hybrid composites under cyclic loading indicate that the nonlinearity in the curve is caused by the plastic deformation of polypropylene in the interphase region. A constitutive model was built to describe the nonlinear shear stress-displacement relation of hybrid composites at different working temperatures. A full suite of temperature-dependent plastic parameters in the model was obtained from cyclic loading-unloading tensile tests. The predicted shear stress–displacement curves agreed well with experimental results from different working temperatures. In addition, the failure mode of hybrid composites varied with working temperature.

Microstructure and Texture Evolutions During Deep Drawing of Mg-Al-Mn Sheets at Elevated Temperatures.

Texture and microstructure evolution of ingot and twin-roll casted Mg–Al–Mn magnesium sheets were examined during deep drawing at elevated temperatures. The twin-roll casted sheets possessed smaller grain sizes and weaker basal intensity levels than the ingot-casted sheets. The strength and elongation at room temperature for the twin-roll casted sheets were greater than those of the ingot-casted sheets. At elevated temperatures, the ingot-casted sheets showed better elongation than the twin-roll casted sheets. Different size and density of precipitates were examined using transmission electron microscopy (TEM) for both ingot-casted and twin-roll-casted sheets. The deep drawing process was also carried out at various working temperatures and deformation rates, and 30 mm/min to 50 mm/min, respectively. The middle wall part of cups were mainly tensile deformation, and the lower bent regions of drawn cups were most thinned region. Overall, the ingot-casted sheets revealed better deep drawability than the twin-roll casted sheets. Microstructure and texture evolution of the top, middle and lower parts of drawn cups were investigated using electron backscatter diffraction. Increased deformation rate is important to activate tensile twins both near the bent and flange areas. Ingot casted sheets revealed more tensile twins than twin-roll casted sheets. Increased working temperature is important to activate non-basal slips and produce the DRXed grain structure in the flange. Dynamic recrystallization were frequently found in the top flanges of the cups. Both tensile twins and non-basal slips contributed to occurrence of the dynamic recrystallization in the flange.

Hydrogen separation from synthesis gas using silica membrane: CFD simulation

In the present article, an axisymmetric two-dimensional (2D) computational fluid dynamic (CFD) model was adapted to predict the efficiency of the silica membrane for hydrogen (H2) separation as a renewable energy source. In this model, continuum flows on the shell and tube sides are defined through the Navier-Stokes and transport of chemical species equations. Components transfer through the silica membrane is characterized by introducing source-sink terms based on activating transport mechanisms. To validate the presented model results related to H2 molar fraction at the retentate and permeate sides were compared with experimental data. The CFD model prognosticates the local information of velocity distribution and the molar fraction of the components. Finally, considering the effects of temperature, pressure difference, gas flow rate, and inner radius of the module on the H2 molar fraction, silica membrane performance was investigated. Moreover, it has been shown that with increasing working temperature from 323 to 473 K, H2 molar fraction at the shell side decreases from 59% to 28.4%, and in the tube side, it rises from 78.8% to 82.8%. On the shell side, it could be seen that H2 permeates better for a low gas flow rate. At the tube side, this parameter has a positive effect on H2 purification. The result of the impact of pressure differences at shell and tube sides was used to indicate the variation in the H2 molar fraction. An increase in pressure difference causes a decrease of H2 molar fraction at the tube side. At the shell side, H2 molar fraction would be decreased with an addition in pressure difference from 1 to 3 bar. Any further pressure difference rise from 3 to 4 bar, make this trend ascending. Likewise, at the shell and tube sides, by enhancing the inner radius of the module, the molar fraction of H2 increases.

Increasing working temperature span in Ni-Mn-Sn-Co alloys via introducing pores

Enhanced magnetic refrigeration performance via introducing pores in a ferromagnetic shape memory Ni-Mn-Sn-Co alloy was demonstrated. The Ni40.7Mn42.9Sn10.4Co6.0 foam, with a porosity of 56% created by replication casting technique, exhibited reduced thermal hysteresis because of the high specific surface area. A maximum magnetic entropy change (ΔSM) 4.7 J/kg·K with a very wide working temperature span (ΔTFWHM) 40 K under 5.0 T were found in the annealed foam. Furthermore, the foam showed a small hysteresis loss (AHL) 17.4 J/kg under 5.0 T. As a result, refrigeration capacity (RC) 155 J/kg and relative cooling power (RCP) 188 J/kg were produced.

Experimental investigation of sandwich glazed solar photovoltaic module

The light and heat energies from the sun are directly converted into electricity either by directly using solar photovoltaic (SPV) module or indirectly using concentrated solar technology system. Photovoltaic (PV) cells is a semiconductor device which is sensitive to temperature. The energy gap of the silicon material reduces when its temperature increases. The decrease in the energy gap of the silicon semiconductor with increasing working temperature can affect the performance of the PV cell. In this article, the working temperature of commercial grade silicon-based solar photovoltaic module as well as sandwich glazed solar photovoltaic module and its impact upon the electricity delivered is discussed. The significant effects of operating temperature, irradiation and wind speed on the PV module temperature were presented. These parameters were used to estimate the electrical performance of the commercial and sandwich glazed PV modules.

Implementation of high color quality, high luminous warm WLED using efficient and thermally stable Rb3AlF6:Mn4+ as red color converter

Here, a high color rendering index (CRI, Ra ∼90) and high luminous efficacy (∼157 lm/W) warm white light-emitting diode (WLED) is realized by using a high performance Rb3AlF6:Mn4+ as red color converter. Rb3AlF6:Mn4+ exhibits high quantum efficiency (QE ∼81%) and high thermal stability (no quench up to 423 K), evidenced to be rooted in Mn4+ residence on distorted and rigid [AlF6] octahedron via contrastive analysis on structure-luminescence relationship between phosphors A2BAlF6:Mn4+ (A/B = K, Rb, Cs). Moreover, this stable Rb3AlF6:Mn4+ ensures tiny color fluctuation of fabricated warm WLED against operating environment with increments of 4.8% and 2.5 for correlated color temperature and Ra in sequence, as an increased working temperature of 100 K. Our findings suggest that this highly efficient and robust red phosphor Rb3AlF6:Mn4+ might be promising candidate for high color rendering and high luminous warm WLED applications.

MEMS based highly sensitive dual FET gas sensor using graphene decorated Pd-Ag alloy nanoparticles for H2 detection

A low power, dual-gate field-effect transistor (FET) hydrogen gas sensor with graphene decorated Pd-Ag for hydrogen sensing applications was developed. The FET hydrogen sensor was integrated with a graphene-Pd-Ag-gate FET (GPA-FET) as hydrogen sensor coupled with Pt-gate FET as a reference sensor on a single sensor platform. The sensing gate electrode was modified with graphene by an e-spray technique followed by Pd-Ag DC/MF sputtering. Morphological and structural properties were studied by FESEM and Raman spectroscopy. FEM simulations were performed to confirm the uniform temperature control at the sensing gate electrode. The GPA-FET showed a high sensing response to hydrogen gas at the temperature of 25~254.5 °C. The as-proposed FET H2 sensor showed the fast response time and recovery time of 16 s, 14 s, respectively at the operating temperature of 245 °C. The variation in drain current was positively related with increased working temperature and hydrogen concentration. The proposed dual-gate FET gas sensor in this study has potential applications in various fields, such as electronic noses and automobiles, owing to its low-power consumption, easy integration, good thermal stability and enhanced hydrogen sensing properties.

Investigation of FinFET as a Temperature Nano-Sensor Based on Channel Semiconductor Type

This paper represents the temperature effect on FinFET transistor and the possibility of using it as a temperature nano-sensor. The MuGFET simulation tool was used to investigate temperature characteristics of the FinFET. Current-voltage characteristics with different values of temperature were simulated. MOS diode connection suggested using the FinFET transistor as a temperature nano-sensor. The final results shows that the best FinFET used as a nano- sensor is with GaAs because it has the greatest ΔΙ (=10.9%) referring to ΔΙ at 25°C, and the best FinFET stable with increasing working temperature is Si-FinFET because it has the lowest ΔΙ (=6%) referring to ΔΙ at 25°C.