Sequential Heat Research Articles

RECYCLING PROCESS OF U3O8 POWDER IN MnO-Al2O3 DOPED LARGE GRAIN UO2 PELLETS

The effect of various process variables on the powder properties of recycled U₃O 8 from MnO-Al₂O₃ doped large grain UO₂ pellets and the effect of those recycled U₃O 8 powders on the sintered density and grain size of MnO-Al₂O₃ doped large grain UO2 pellets have been investigated. The evolution of morphology, size, and BET surface area of the recycled U₃O 8 powders according to the respective variation of the thermo-mechanical treatment variables of oxidation temperature, powder milling, and sequential cyclic heat treatment of oxidation and then reduction was examined. The correlation between the BET surface area of recycled U₃O 8 powder and the sintered pellet properties of MnO-Al₂O₃ doped pellets showed that the pellet density and grain size of doped pellets were increased and then saturated by increasing the BET surface area of the recycled U₃O 8 powder. The density and grain size of the pellets were maximized when the BET surface area of the recycled U₃O 8 powder was in the vicinity of 3㎡/g. Among the process variables applied in this study, the cyclic heat treatment followed by low temperature oxidation was a potential process combination to obtain the sinter-active U₃O 8 powder.

Ray-Thermal Sequential Coupled Heat Transfer ANALYSIS of Porous Media Receiver for Solar Dish Collector

For the sake of reflecting the concentrated heat flux distribution boundary condition as genuine as possible during simulation, the sequential coupled optical-thermal heat transfer analysis is introduced for porous media receiver. During the sequential coupled numerical analysis, the non-uniform heat flux distribution on the fluid entrance surface of porous media receiver is obtained by Monte-Carlo ray tracing method. Finite element method (FEM) is adopted to solve energy equation using the calculated heat flux distribution as the third boundary condition. The dimensionless temperature distribution comparisons between uniform and non-uniform heat flux distribution boundary conditions, various porosities, and different solar dish concentrator tracking errors are investigated in this research.

유도가열시 중형 크랭크샤프트의 열전달 해석

본 연구는 중형 크랭크샤프트 제작 과정에서 환봉을 가열하기 위한 최적의 유도가열조건을 결정하기 위한 것으로, 4가지 가열조건(가열코일 개수, 위치 등)에 대하여 수치해석적인 방법을 사용하여 전자기장 및 열전달해석을 순차적으로 수행하였다. 이러한 수치해석 결과로부터 일정시간 가열 후 크랭크샤프트 환봉 가열부에 발생하는 최고온도와 두께에 따른 내, 외부 최소 온도차를 평가하여 현장에 적용 가능한 가열코일의 위치 및 개수 등의 유도가열조건을 결정하였다. This study was peformed to determine optimum induction heating conditions for a round bar of crankshaft. Four induction heating conditions were proposed and evaluated, employing numerical method, based on electromagnetic and sequential heat transfer analyses, resulting in optimum induction heating conditions which are finally proposed based on peak temperatures at heating zone and minimum temperature gradient through thickness of a round bar after 1 hour induction heating.

β-Lactoglobulin conformation and mixed sugar beet pectin gel matrix is changed by laccase

Sugar beet pectin (SBP) and β-lactoglobulin (BLG) contain ferulic acid and tyrosine, respectively, potential substrates for laccase. Dispersions of BLG were treated with laccase and/or heat and SBP to assess potential for ferulic acid in SBP to influence laccase conjugation of BLG. Changes were investigated by size exclusion chromatography combined with multi angle laser light scattering (HPSEC-MALLS), refractive index (RI) and UV detector, particle size and ζ-potential analysis. Molecular weight (MW) of BLG decreased from 3.7 × 104 to 2.9 × 104 and root mean square (RMS) decreased from 41 to 36 after laccase treatment. The slope of a conformation plot increased from 0.35 to 0.72, indicating a change in shape in laccase treated BLG to more random coil. While laccase did not affect MW of BLG, MW of BLG increased after sequential heat and laccase treatment to 2.9 × 106 and 4.4 × 106, respectively. Free thiol (SH) increased by heat and laccase treatment of BLG; tyrosine in BLG increased only by heat. An increased MW and decreased ferulic acid in SBP was observed in the presence of BLG and laccase. The increase in MW was attributed to entrapment of BLG in SBP cross-linked matrix catalyzed by laccase.

Synthesis and Characterization of Hollow Cadmium Oxide Sphere with Carbon Microsphere as Template

Cadmium Oxide (CdO) hollow spheres have been synthesized by using carbon microsphere as sacrificial template. The products were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). The average diameter and shell thickness of as-prepared hollow spheres are about 600 nm and 50 nm, respectively. The formation of hollow spheres was investigated and it was found that the shell formed when the heating temperature reached about 673 K and the sequential heat treatment could remove the carbon template. Moreover, the influence of other experimental parameters including concentration (0.1-5 M) and type of cadmium salts (cadmium chloride, cadmium acetate and cadmium nitrate, etc.) as well as type of solvents (water, ethanol and dimethylfomamide) were also investigated.

Porous Y2O3 microcubes: synthesis and characterization

In this work, a facile route using a simple solvothermal reaction and sequential heat treatment process to prepare porous Y2O3 microcubes is presented. The as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), thermogravimetric analysis (TG), and differential thermal analysis (DTA). The thermal decomposition process of the Y2O3 precursor was investigated. SEM results demonstrated that the as-prepared porous Y2O3 microcubes were with an average width of about 20 μm and thickness of about 8 μm. It was found that the morphology of the Y2O3 precursor could be readily tuned by varying the molar ratio of S2O82− to Y3+. Y2O3:Eu3+ (6.6%) microcubes were also prepared and their photoluminescence properties were investigated.

An Fe 3O 4–FeO–Fe@C composite and its application as anode for lithium-ion battery

An Fe 3O 4–FeO–Fe@C composite material has been successfully synthesized by a one-pot hydrothermal method without any templates and a sequential heat treatment process. X-ray diffraction, Raman spectrometry, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and galvanostatic cell cycling have been used to characterize the structure and electrochemical performance of the as-prepared Fe 3O 4–FeO–Fe@C composite. The electrode shows a stable and reversible capacity of over 600 mAh g −1 at a current of 53 mA g −1 for up to 60 cycles, which could be ascribed to the unique double-layer core–shell and embedded structures.

Techno-economic feasibility of absorption heat pumps using wastewater as the heating source for desalination

The utilization of low-grade heat could significantly reduce energy consumption in thermal desalination plants. This paper studies the feasibility of using low-grade heat for thermal desalination via a hybrid absorption heat pump system, in which ammonia–water is the working fluid. A thermodynamic model was proposed to simulate the operation for freshwater production of 5000T/day using multiple effect distillation (MED) technology. Results from the evaluation showed that the performance and waste-water usage are affected by operating pressures and temperatures. Based on Net Present Value evaluation, the economic profitability could be achieved at recommended operating conditions of absorption pressure (<25bar) and generation temperature (>30°C) at a generation pressure 5bar. A case study is presented in which water at 90°C, discharged from process industry in the Sheffield region, is used for generating 20,000T/day of freshwater. The system proposed consisted of four-stage sequential heat pumps with different operating configurations. These served as individual MED stages. The coefficients of performance were evaluated to be 3–11. According to the specific power consumption, the proposed system is a competitive technology compared with reverse-osmosis technology. Economic profitability could be achieved in 3years.

Preparation and Characterization of 3D Flower-like La2O3 Nanostructures

In this work, a facile route using a simple solvothermal reaction and sequential heat treatment process to prepare 3D La2O3 flower-like nanostructures without employing templates or matrices for self-assembly is presented. The as-synthesized products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), highresolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG), differential thermal analysis (DTA), and Fourier transformation IR (FTIR). SEM results demonstrate that the as-prepared flower-like precursor with average size of 5- 7 μm in diameter is composed of numerous nanoplates with a thickness of about 100 nm. Influencing factors such as solvothermal reaction temperature, surfactants, reaction time, and solvents were systematically investigated. 3D flower-like La2O3 nanostructures with many holes on the petals were obtained after calcinations of the flower-like precursor at 800 °C for 4 h. The BET surface area of the flower-like La2O3 nanostructures is 9.98 m2/g. Eu3+ doped flower-like La2O3 nanostructures were also prepared employing the same preparation process. The flower-like La2O3:Eu3+ nanostructures show a strong red emission corresponding to 5D0 -7F2 transition (625 nm) of Eu3+ under ultraviolet excitation (267 nm). The possible formation mechanism for the 3D flower-like precursor was briefly discussed. Keywords: Characterization, lanthanum oxide, nanomaterials, porous, self-assembly, solvothermal synthesis, rare earth, flower-like, nanostructures, photoluminescence

Magnetic and electrical properties of Mn–Zn ferrites synthesized by combustion method without subsequent heat treatments

Nanocrystalline ferrites MnxZn1−xFe2O4 (x = 0.0–1.0) were prepared by the combustion method without sequential heat treatment. As-synthesized MnxZn1−xFe2O4 ferrites, characterized by x-ray diffraction (XRD), have demonstrated a highly pure phase of spinel structure. From the analysis of XRD data with Scherrer’s formula, the average crystallite size is about 27–37 nm and the lattice parameters range from 8.457 to 8.515 Å. The saturated magnetization of the Mn–Zn ferrite samples, measured by vibrating sample magnetometer, is varied with the content of manganese. The high frequency electromagnetic properties were investigated by impedance spectra methods and the conduction mechanism was also discussed. The results imply that this combustion method without further thermal treatment is relatively efficient and economical as compared to conventional methods for industrial synthesis of ferrites in high frequency electromagnetic devices applications.

Double‐Shelled Mn2O3 Hollow Spheres and Their Application in Water Treatment

AbstractDouble‐shelled Mn2O3 hollow spheres have been successfully prepared on a large scale by using core‐shell‐structured MnCO3 microspheres as sacrificial templates. This new method is based on an inward oxidation/etching treatment and sequential heat treatment in air. The as‐prepared double‐shelled Mn2O3 hollow spheres consist of small nanoparticles with a size of ca. 50 nm, and there are many nanopores among the particles. As the double‐shelled Mn2O3 hollow spheres were employed in water treatment, they could remove about 86 % of phenol without any other additives.

Inorganic Polymer Matrix Composite Strength Related to Interface Condition

Resin transfer molding of an inorganic polymer binder was successfully demonstrated in the preparation of ceramic fiber reinforced engine exhaust valves. Unfortunately, in the preliminary processing trials, the resulting composite valves were too brittle for in-engine evaluation. To address this limited toughness, the effectiveness of a modified fiber-matrix interface is investigated through the use of carbon as a model material fiber coating. After sequential heat treatments composites molded from uncoated and carbon-coated fibers are compared using room temperature 3-point bend testing. Carbon-coated Nextel fiber reinforced geopolymer composites demonstrated a 50% improvement in strength, versus that of the uncoated fiber reinforced composites, after the 250 °C postcure.

Dynamical and quasistatic structural relaxation paths in Pd40Ni40P20 glass

By sequential heat treatment of a Pd40Ni40P20 metallic glass at temperatures and durations for which α-relaxation is not possible, dynamic, and quasistatic relaxation paths below the glass transition are identified via ex situ ultrasonic measurements following each heat treatment. The dynamic relaxation paths are associated with hopping between nonequilibrium potential energy states of the glass, while the quasistatic relaxation path is associated with reversible β-relaxation events toward quasiequilibrium states. These quasiequilibrium states are identified with secondary potential energy minima that exist within the inherent energy minimum of the glass, thereby supporting the concept of the sub-basin/metabasin organization of the potential-energy landscape.

Microemulsions as Nanoreactors To Produce Whey Protein Nanoparticles with Enhanced Heat Stability by Sequential Enzymatic Cross-Linking and Thermal Pretreatments

Sequential enzymatic cross-linking and heat pretreatments were used in this work to enhance the heat stability of whey protein isolate (WPI). In the first route, WPI was cross-linked by transglutaminase before incorporation in microemulsions for heat pretreatment at 90 degrees C for 20 min. In the second route, WPI was cross-linked by transglutaminase within microemulsions before thermal pretreatment. Particles produced from the two routes were different in dimension and heat stability and were also affected by the ratio of WPI and enzyme and cross-linking duration. At appropriate conditions, for example, 10 h of cross-linking by transglutaminase equivalent to 5% mass of WPI using the first route, a 5% dispersion (pH 6.8 and 100 mM NaCl) of the produced nanoparticles remained clear after heating at 90 degrees C for 20 min. In comparison, nanoparticles produced by thermal pretreatment only in a microemulsion corresponded to a translucent, flowable dispersion, whereas native WPI formed a gel. This novel approach can be used to manufacture heat-stable whey protein ingredients for clear beverage applications.

OS-C3: Numerical Study of Stratification on HCCI Combustion for Higher Load Extension(OS-C The Role of Heterogeneity of mixture on HCCI and PCCI Combustion,Organized Session Papers)

This paper studied the potential of HCCI higher load extension by using there types of stratified charge, including temperature (thermal) stratification, concentration (fuel) stratification and species (EGR) stratification. To isolate the influence of three stratifications on HCCI engine performance, HCCI combustion processes with different equivalence ratios, stratification degree, EGR ratios were simulated. The results show that stratification leads to earlier ignition timing, sequential heat release, longer combustion duration, lower rate of pressure rise compared to pure homogeneous cases at same load. However, both fuel stratification and EGR stratification lead to high NO_x. Temperature stratification is most effective one to significantly reduce pressure rise rate during CI combustion process with least negative effect of high NO_x emission or incomplete combustion. With limit of maximum pressure rise rate at 5bar/CA and maximum NO_x emissions at 100ppm, the maximum IMEP of pure HCCI without EGR is 1.86bar, the maximum IMEP can be further extended to 5.4bar using temperature stratification and EGR dilution, under natural aspiration conditions.

Formation of the Bi-2212 phase in a BiSrCaO thick film screen printed on Cu∕Ni∕Cu substrate

To adopt Cu as a substrate material for Bi superconductors, Ni and Cu were electroplated on a Cu sheet; in this structure, Ni restrained the oxidation of Cu, and Cu acted as the source element to provide Cu oxides. Superconducting phases such as Bi-2212 were obtained by sequential heat treatments in Ar gas and Ar–(20vol%)O2 gas. Particularly, the (00l) plane of the Bi-2212 phase tended to develop in the exterior region close to the free surface rather than in the interior region. The critical onset temperatures of the specimens produced by the sequential heat treatments ranged from 73.4to78.5K.

Finite element-based life prediction for high-temperature cyclic loading of a large superplastic forming die

The thermomechanical, time-dependent, elastic-plastic creep behaviour of a representative tool in a high-temperature superplastic forming press has been simulated using a sequential finite element-based heat transfer and mechanical stress analysis approach. The heating and cooling aspects of the heat transfer model have been previously validated against laboratory measurements. This paper focuses on the prediction of die life based on this model. The determination and modelling of the high-temperature mechanical properties of the materials and die are described for both so-called (a) major cycles, relating to die heat-up and cool-down from and to ambient temperature, and (b) minor cycles, relating to die heat-up and cool-down associated with part removal and blank insertion. A creep-fatigue life prediction method using non-linear damage summation is developed and applied to the die-life problem. Isothermal fatigue and creep-fatigue interaction tests at 700 and 900 °C on 40%Ni-20%Cr die material XN40F are carried out to estimate the required strain-life relationships.

Prediction of microstructure evolution of Al–1% Mg alloy during hot forming and sequential heat treatment

The microstructure evolution during hot forming and sequential heat treatment was simulated to guide the process design by using the finite element method (FEM). The microstructure change under varying deformation conditions during hot forming was investigated. These formulations were implemented into a commercial finite element code to analyze microstructure evolution during hot forming and heat treatment. Static recrystallization, dynamic recrystallization and meta-dynamic recrystallization were taken into account. The FE module was applied to analyze the microstructure change of Al–1% Mg alloy. Al–1% Mg is very different to the steels since it does not appear to undergo dynamic (or, therefore, metadynamic) recrystallization because of the high rate of dynamic recovery. Static recrystallization was considered in the paper. The influence of transient strain rate deformation conditions on the deformed microstructure of Al–1% Mg was studied by using numerically analytical method and FEM. The simulated stress and microstructure change were compared with published experimental and analytical results. The evolution of grain structure for Al–1% Mg steering link forging (1999 German Forging Industry Association Benchmark) and sequential heat treatment was simulated using the 3D FE simulator combined with a microstructure module. The forging with finer grain structure is obtained by annealing for 2 h at 400 °C.

Variation in electrical properties of the Cd1 − x ZnxTe crystals as a result of heat treatment

The impurity-defect system in the Cd1 − x ZnxTe crystals (0.02 ≤ x ≤ 0.15) is analyzed prior to and after heat treatment at 720–1170 K. It is found that the conductivity in most of these crystals is governed by two types of acceptors, A 1 (E V = 0.03–0.05 eV) and A 2 (E V = 0.12–0.15 eV). The variation in electrical properties of the crystals after heat treatment depends on the concentration of background impurities in the starting material and the degree of compensation of acceptor A 1. An increase in the resistivity and homogeneity of the samples is observed after two sequential heat treatments.

Heat transfer behavior in the impingement zone under circular water jet

In this study an iterative and sequential inverse heat transfer analysis procedure is developed and implemented into a two-dimensional finite element program. The developed program is used to determine the heat fluxes at the stagnation points of stationary hot plates cooled by impingement water jets in an industry scale test facility. Analysis of data shows that the heat transfer behavior at the stagnation is mainly affected by water temperature and hardly affected by water flow rate with mild effect from steel grade. The features of boiling curves and the typical values obtained are in good agreement with data in the literature.