5,418 research outputs found
Experimental study on heat transfer characteristics of metal foam/paraffin composite PCMs in large cavities: Effects of material types and heating configurations
No full textThis study explores the effects of material types and structural parameters of metal foam, and heating config-urations on the evolution of melting front, heat transfer characteristics, and temperature distribution of metal foam/paraffin composite phase change materials (PCMs) in large cavities. Copper and iron foams were used as the heat transfer enhancement medium, while paraffin with a melting point of 45 C was chosen as the PCM to store heat. This study identified the heat transfer regimes in large cavities during the melting process. The experimental results on different heating configurations indicated that different from small cavities, both con-duction and convection regimes played a fundamental role in the melting process. In addition, the heating configuration controlled the evolution of the melting front of the pure PCM and composite PCM. On the basis of these results, a non-dimensional correlation validated against a large dataset of experiments was fitted to model the melting process of the composite PCMs
Role of partial and gradient filling strategies of copper foam on latent thermal energy storage: An experimental study
No full textLow thermal conductivity of most phase change materials (PCMs) limits the practical application of latent thermal energy storage. This study aims to investigate the role of the partial and gradient filling strategies of copper foam on the heat transfer characteristic of latent thermal energy storage. A visual test rig was built to capture the evolution of the melting front over time. An infrared camera and T-type thermocouples measured the temperature fields and temperature profiles at specific points, respectively. The melting rate, temperature distribution and storage efficiency were investigated and analyzed in detail. The melting rate of PCM first increases and then decreases with the increase of filling ratio, and reaches the maximum value when the filling ratio is 5/6. The application of partial filling strategy reduces the maximum temperature difference of PCM and enhances the stability of the system. In the application of gradient filling strategy, copper foam with larger porosity should be arranged close to the heating wall or above the cavity. Partial and gradient strategy can increase the melting rate of PCM by reducing or maintaining the filling quantity of metal foam, which is of great significance for the practical application of metal foam in latent energy storage. (C) 2022 Elsevier Ltd. All rights reserved
An experimental investigation on performance of microencapsulated phase change material slurry in ground heat exchanger
No full textAs a promising alternative to conventional heat transfer fluids, microencapsulated phase change material slurry (MPCS) was applied in ground heat exchanger (GHE) in this paper. A sandbox system embedded with horizontal serpentine GHE was installed and MPCS using N-eicosane (C20H42) as phase change material is prepared. To explore the merits of MPCS, a comparison study between performance of water and MPCS was conducted. In addition, the enhanced heat transfer mechanism of MPCS were studied by comparing performance of MPCS with different inlet temperature and particle concentration. The experimental results indicate that the heat transfer rate and pumping consumption of 25 wt% MPCS with inlet temperature of 30 ?C are 10.5 and 2.8 times that of water, respectively. The heat load-to-pumping consumption ratio has an enhancement of 3.73 times in com-parison to water. Obviously, considering the phase transition process, MPCS can efficiently improve thermal performance of GHE. However, in the non-phase transition temperature range, the performance of MPCS is even worse than that of water. The comprehensive performance factor of 15 wt% MPCS and 25 wt% MPCS with inlet temperature of 38 ?C declined by 45.6% and 36.9% in comparison with pure water
含液化木質素水性PU樹脂之膠合及塗裝性能
No full textIn this study, dealkaline lignin was liquefied in polyethylene glycol/glycerol cosolvent with hydrochloric acid as a catalyst. The waterborne polyurethane resins (PU) were prepared with a prepolymer mixing process and part of the polytetramethylene ether glycol (PTMG) was replaced with liquefied lignin (LL). The molar ratios of -OH/-OH for LL and PTMG was set as 0/10, 3/7, 4/6 and 5/5. The properties of resin solution and dry film of waterborne PU resins were evaluated as well as the feasibility of using them as adhesives and coatings were investigated. The result shows that the waterborne PU resins were non-Newtonian fluids with the behavior of shear-thinning (Pseudoplastic fluid). Increasing the rate of LL in waterborne PU resins, the viscosity and the particle diameter of liquid resins, and the elastic modulus of dried films increased. However, the tensile strength and elongation at break decreased. Waterborne PU resins containing LL can be used for gluing wood to wood and wood to nonporous materials. It had the best gluing performance for that prepared with the -OH/-OH molar ratio of LL/PTMG as 4/6. All of the waterborne PU resins showed good bending resistance when used as coatings. The hardness of coatings increased, but the abrasion resistance and adhesion decreased as the rate of LL increasing.本研究將脫鹼木質素以聚乙二醇／丙三醇混合液為溶劑，鹽酸為催化劑進行液化處理，並以此液化木質素（Liquefi ed ligni
Natalia LL - artystka neoawangardowa
No full textThe paper shows Natalia Lach-Lachowicz (Natalia LL) as a neo avant-garde artist whose works in a specific maximalistic way are very close to the main currents of avant-garde trends: new mediality (photography), minimalism, conceptualism, performance, bodyart, pop-art, and feminist art. The author of the article concentrates mainly on the mutual influences of conceptualism, consumptionism, and feminism in Natalia LL’s works and pays attention to the emancipatory potential of her works of the seventies and the eighties
Improved Evaluated Nuclear Data in the Resonance Region by Combining Energy Dependent Measurements and Depletion Calculations: Application to Pu-239+n, Pu-240+n and Pu-241+n
No full textThe determination of resonance parameters for neutron interactions with material is a complex process. In most cases it is very difficult to de termine an ac curate es timate of th e fu ll se t of parameters from an analysis of energy dependent cross section data. In this work, a procedure is presented to adjust the resonance parameters for neutron interaction with Pu-239, Pu-240 and Pu-241 by combining the results of depletion calculations, criticality benchmarks together with energy dependent cross section data from the EXFOR database. The addition of microscopic data in the adjustment is different f rom t he g enerally a ccepted a pproach a nd t he k ey n ovelty o f t his w ork as it ensures that the results of the procedure are in agreement with the microscopic data within the margins specified in the constraints. The overestimation of the reactivity loss with exposure of a recent test version of the JEFF nuclear data library (JEFF-4T2.2) is improved drastically together with the underestimation of the Pu-239 concentration. Both kin f and Pu-239 obtained with JEFF-3.1.1 and JEFF-4T2.2 for the VERA-1C pincell depletion problem are now in agreement, e.g. with 100 pcm and 1% respectively, through the exposure considered.LR
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MCSNA: Experimental Benchmarking of Pu Electronic Structure
No full textThe objective of this work is to develop and/or apply advanced diagnostics to the understanding of aging of Pu. Advanced characterization techniques such as photoelectron and x-ray absorption spectroscopy will provide fundamental data on the electronic structure of Pu phases. These data are crucial for the validation of the electronic structure methods. The fundamental goal of this project is to narrow the parameter space for the theoretical modeling of Pu aging. The short-term goal is to perform experiments to validate electronic structure calculations of Pu. The long-term goal is to determine the effects of aging upon the electronic structure of Pu. Many of the input parameters for aging models are not directly measurable. These parameters will need to be calculated or estimated. Thus a First Principles-Approach Theory is needed, but it is unclear what terms are important in the Hamiltonian. (H{Psi} = E{Psi}) Therefore, experimental data concerning the 5f electronic structure are needed, to determine which terms in the Hamiltonian are important. The data obtained in this task are crucial for reducing the uncertainty of Task LL-01-developed models and predictions. The data impact the validation of electronic structure methods, the calculation of defect properties, the evaluation of helium diffusion, and the validation of void nucleation models. The importance of these activities increases if difficulties develop with the accelerating aging alloy approach
THE K–LL AUGER SPECTRUM OF <sub>94</sub>Pu<sup>239</sup>
No full text The K–LL Auger spectrum of 94Pu239 has been examined using a high resolution π√2 β-ray spectrometer with a proportional counter detector. Seven lines have been observed in the Auger spectrum with the following energies and relative intensities.[Formula: see text]The presence of seven lines in this K–LL Auger spectrum is in disagreement with theoretical predictions based on pure j–j coupling and supports, rather, the recent theoretical treatment of Asaad and Burhop. The energies of the observed lines are in satisfactory agreement with their theoretical predictions but discrepancies exist in the relative intensities. </jats:p
Adenocarcinoma primário de duodeno: relato de dois casos do serviço de gastroenterologia cirúrgica do Hospital do Servidor Público Estadual "Francisco Morato de Oliveira" - IAMSPE - São Paulo - SP.
No full textTrabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de Clínica Cirúrgica, Curso de Medicina, Florianópolis, 198
Energy flux in isotropic turbulence under large variations of external forcing
No full textWe investigate the response of energy flux in isotropic turbulence to step-function like perturbation in external forcing at large length scales. From both physical experiments and direct numerical simulations, we measured the evolution of the Eulerian velocity structure functions, such as , , before and after the perturbation in forcing. In both cases, we observed the cascade of the energy excess at large scales cascade through scales to the dissipative range, which can be used to study the dynamics of the cascade, and in particular, to estimate the relevant time scales
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