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101.
The increasing interest in the utilization of shallow geothermal energy comes with the wish for better knowledge about the factors influencing its efficiency. For this purposes we focused on the subsurface condition's influence on the use of borehole heat exchangers (BHEs) coupled with a heat pump for heating purposes, since this is the most popular heat-extracting technique. We created maps showing the potential for this technique provided by the thermal underground properties. Therefore, we established an underground model for two study areas in south-western Germany with different geological settings using a geographic information system (GIS). The subsurface has been divided into layers with similar thermal properties based on geological, hydrogeological and lithological information. The layers have been attached with specific heat extraction values, according to the German VDI guideline 4640. For depths of 50 and 100 m, the weighted mean value of the specific heat extraction was calculated and presented within maps. These maps point out how the heat-extraction potential differs within and between the study areas and how it depends on depth. 相似文献
102.
103.
In this work, the optimal time-varying allocation of steam in a large-scale industrial isocyanate production process is addressed. This is a problem that falls into the category of real-time optimization (RTO). The application of RTO in practice faces two problems: First the available rigorous process models may not be suitable for use in real-time connected to the process. Second, there is always a mismatch between the predictions of the model and the behavior of the real plant. We address the first problem by training a neural net model as a surrogate to data generated by a rigorous simulation model so that the model is simple to implement and short execution times result. The second problem is tackled by adapting the optimization problem based on measured data such that convergence to the optimal operating conditions for the real plant is achieved. 相似文献
104.
Dreyer A Ennen I Koop T Hütten A Jutzi P 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(21):3075-3086
Routes are presented for synthesizing nano- and mesostructured β-tin particles in the form of monocrystalline spheres, cubes, and bars, as well as polycrystalline rods and needles, by the decomposition of decamethylstannocene in organic solvents under various conditions. The formation of the observed shapes is based on the presence of liquidlike and of partly crystalline droplets. These particle stages allow structure-determining processes such as entire coalescence, oriented superficial coalescence or superficial induced crystallization. Entire coalescence and oriented superficial coalescence take place in the absence of surfactants; the superficially induced crystallization occurs in the presence of ionic additives. The observed tin morphologies depend on the competition between droplet growth and crystallization behavior. The different tin particles are investigated by electron microscopy (SEM, TEM, HRTEM), selected area electron diffraction (SAED), and differential scanning calorimetry (DSC). 相似文献
105.
Inga Ringdalen Vatne Erling ØstbyChristian Thaulow Diana Farkas 《Materials Science and Engineering: A》2011,528(15):5122-5134
We have investigated fracture in bcc-Fe through multiscale simulations. The quasicontinuum (QC) method with an embedded atom method (EAM) interatomic potential is applied. The analyses have been carried out assuming different crystallographic orientations and different T-stress under Mode I loading. Both anisotropic and isotropic formulations of the modified boundary layer (MBL) approach has here been investigated and compared. The results show that the mechanisms at the crack tip and the critical stress intensity factor KIc are sensitive to both the crystallographic orientation and whether or not the formulation of the boundary conditions are isotropic or anisotropic. Mechanisms such as cleavage crack propagation, twinning, and dislocation emission are observed in the analyses. A short literature review on atomistic and multiscale simulations of fracture in bcc-Fe has been performed and evaluated, and also compared with the current results. 相似文献
106.
Jörg Weiss-Ungethüm Inga BürgerNiko Schmidt Marc LinderJosef Kallo 《International Journal of Hydrogen Energy》2014
In high temperature proton exchange membrane (HT-PEM) fuel cells, waste heat at approximately 160 °C is produced, which can be used for thermal integration of solid state hydrogen storage systems. In the present study, an HT-PEM fuel cell stack (400 W) with direct liquid cooling is characterized and coupled to a separately characterized sodium alanate storage tank (300 g material). The coupled system is studied in steady state for 20 min operation and all relevant heat flows are determined. Even though heat losses at that specific power and temperature level cannot be completely avoided, it is demonstrated that the amount of heat transferred from the fuel cell stack to the cooling liquid circuit is sufficient to desorb the necessary amount of hydrogen from the storage tank. Furthermore, it is shown that the reaction rate of the sodium alanate at 160 °C and 1.7 bar is adequate to provide the hydrogen to the fuel cell stack. Based on these experimental investigations, a set of recommendations is given for the future design and layout of similar coupled systems. 相似文献
107.
Optimization of hydrogen charging process parameters for an advanced complex hydride reactor concept
Complex hydrides are identified as promising hydrogen storage media with gravimetric capacities up to 10 wt.%. However, the high temperatures required for the initiation of their hydrogen charging process and their slow kinetics prevent their integration in many practical applications. This paper discusses the challenge of addressing these issues by combining this kind of materials with the appropriate metal hydrides. For this purpose, the complex hydride, 2LiNH2–1.1MgH2–0.1LiBH4–3 wt.% ZrCoH3 (CxH) and the metal hydride, LaNi4.3Al0.4Mn0.3 (MeH) have been selected as reference materials. The studied configuration corresponds to a tubular reactor where the metal hydride and the complex hydride, separated by a gas permeable layer, are embedded respectively in the centre and the annular ring of the reactor. A 1-dimensional finite element model and a dimensionless number comparing the dominance of the kinetics and the heat transfer processes have been developed to optimize the charging process for different thicknesses and volumetric ratios of the studied materials. For the selected cases, the influence of the thermal properties of the complex hydride and the operating conditions on the charging process is assessed. A sensitivity study has shown that the thermal conductivity of the CxH is the most important parameter influencing the hydrogen storage rate if thick MeH and CxH beds are considered. In contrast, the hydrogen loading time is significantly improved by increasing the coolant temperature for small thicknesses of the two storage media. Thereafter, the gravimetric and volumetric capacities resulting from the scale up of the optimized configurations to store 1 kg of hydrogen are calculated and results are discussed taking into account the interdependence of the different studied parameters. 相似文献
108.
Mordechai Shacham Inga Paster Neima Brauner 《American Institute of Chemical Engineers》2013,59(2):420-428
Data analysis and prediction of pure component properties of long‐chain substances is considered. The emphasis is on homologous series and properties for which insufficient data are available. A two‐stage procedure is recommended, whereby a linear (or nonlinear) quantitative structure–property relationship (QSPR) is fitted to a “reference” series, for which an adequate amount of precise data is available. This QSPR should represent correctly both the available data and the asymptotic behavior of the property. In the second stage a quantitative property‐property relationship (QPPR) is derived to represent the predicted property values of a “target” series in terms of the property values of the reference series. The procedure is applied for properties which are highly correlated with the number methylene groups in homologous series: and . It is shown that the method is very useful for consistency analysis of property data and enables a reliable prediction of and , and, thus, also of for long‐chain substances. © 2012 American Institute of Chemical Engineers AIChE J, 59: 420–428, 2013 相似文献
109.
Inga Audzevičiūtė-Liutkienė Vitalija Masteikaitė Milda Jucienė Virginija Sacevičienė Rimantas Barauskas Saulius Diliūnas 《纺织学会志》2019,110(7):1051-1058
The article presents the tensile forces caused knitted fabrics’ deformations non-uniformity analysis. At first, the tensile behaviour was analysed by applying new method based on specific Y-shaped and stretching specimen. This shape of specimen allows to fulfil wearing conditions of apparel made of knitted fabrics. After this, the article analyses research conditions and knitted fabrics’ deformability physical characteristics and determines longitudinal, transverse and angular deformations. The deformations properties were evaluated using graphic and numerical methods. Investigations have shown that elastane fibres significantly influenced fabric deformability, dimensional changes and deformations’ non-uniformity. Experiments have also shown that Y-shaped specimen tensile test is a simple, universal and reliable method suitable to obtain quantitative information about textile materials deformability. 相似文献
110.
Tatjana Dedova Ilona Oja Acik Svetlana Polivtseva Malle Krunks Inga Gromyko Kaia Tõnsuaadu Arvo Mere 《Ceramics International》2019,45(2):2887-2892
ZnO is an important inorganic material for numerous applications. Different physical and chemical methods have been applied to deposit ZnO. Spray pyrolysis method being simple, rapid and low-cost is amongst the many options and has been chosen for this study. Fabrication of ZnO nanorods crystals by chemical spray pyrolysis was performed using an acidic solution of ZnCl21 or a basic ammonia-containing solution of ZnCl22. All layers were studied using X-ray diffractometry and Scanning Electron Microscopy. The formation of ZnO nanorods from 2 appeared at 450?°C, whereas spraying acidic solution 1 yielded ZnO nanorods like morphology at 550?°C.Thermal decomposition of precursors for ZnO layers prepared by de-watering of acidic aqueous solution of ZnCl2 with pH =?3 (1) and basic solution of ZnCl2 and NH4OH with pH =?10 (2) was monitored by simultaneous thermogravimetric and differential thermal analysis (TG/DTA) in air coupled online with evolved gas analyses by Fourier transformed infrared spectroscopy (FTIR).The precursor (1) is ZnCl2 *nH2O; the precursor (2) is a mixture of (NH4)3(ZnCl4)Cl, Zn(NH3)2Cl2, NH4Cl(NH3)3 and Zn(OH)2 phases. The thermal decomposition of (1) and (2) in the temperature range of 30–700?°C consists of two steps with total mass losses of 86.2% and 93.8%, respectively. The main evolved gases from (1) are H2O and HCl, whereas the main evolved gases from (2) are H2O, NOx and NH3. Degradation of (1) and (2) is completed by 670 and 620?°C, respectively. The final decomposition product of (1) and (2) at 700?°C is ZnO.This study shows that the use of basic solutions enables to decrease the temperature of ZnO formation and the deposition temperature of ZnO nanorods layers. 相似文献