| 1. |
- Danish, Muhammad, et al.
(författare)
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An efficient catalytic degradation of trichloroethene in a percarbonate system catalyzed by ultra-fine heterogeneous zeolite supported zero valent iron-nickel bimetallic composite
- 2017
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 531, s. 177-186
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Tidskriftsartikel (refereegranskat)abstract
- Zeolite supported nano iron-nickel bimetallic composite (Z-nZVI-Ni) was prepared using a liquid-phase reduction process. The corresponding surface morphologies and physico-chemical properties of the Z-nZVI-Ni composite were determined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy dispersive X-ray spectra (EDS), Brunauer Emmett Teller (BET) adsorption, wide angle X-ray diffractometry (WA-XRD), and Fourier transform infrared spectroscopy (FTIR). The results indicated high dispersion of iron and nickel nano particles on the zeolite sheet with an enhanced surface area. Complete destruction of trichloroethene (TCE) and efficient removal of total organic carbon (TOC) were observed by using Z-nZVI-Ni as a heterogeneous catalyst for a Fenton-like oxidation process employing sodium percarbonate (SPC) as an oxidant. The electron spin resonance (ESR) of Z-nZVI-Ni verified the generation and intensity of hydroxyl radicals (OH center dot). The quantification of OH center dot elucidated by using p-chlorobenzoic acid, a probe indicator, confirmed the higher intensity of OH center dot. The transformation products were identified using GC-MS. The slow iron and nickel leaching offered higher stability and better catalytic activity of Z-nZVI-Ni, demonstrating its prospective long term applications in groundwater for TCE degradation. (C) 2016 Elsevier B.V. All rights reserved.
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| 2. |
- Ding, J., et al.
(författare)
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Theoretical prediction of the local structures and transport properties of binary alkali chloride salts for concentrating solar power
- 2017
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 39, s. 380-389
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive molecular simulations have been carried out to compute local structures and transport properties of different components of binary NaCl-KCl over a wide operating temperature range. The partial radial distribution functions, coordination number curves and angular distribution functions were calculated to analyze the influence of temperature and component on local structures of molten Alkali Chlorides. Transport properties were calculated by using reverse non-equilibrium molecular dynamics (RNEMD) simulations including densities, shear viscosity and thermal conductivity. The results show that ion clusters are considered to be formed and the distance of ion clusters become larger with increasing temperature which has great influence on macro-properties. The calculated properties have a good agreement with the experimental data, and similar method could be used to computationally calculate the properties of various molten salts and their mixtures.
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| 3. |
- Farooq, U., et al.
(författare)
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Efficient transformation in characteristics of cations supported-reduced graphene oxide nanocomposites for the destruction of trichloroethane
- 2017
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Ingår i: Applied Catalysis A. - : Elsevier B.V.. - 0926-860X .- 1873-3875. ; 544, s. 10-20
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were conducted to investigate the use of graphene-oxide supported metallic nanocomposites for improving the degradation of trichloroethane (TCA) by sodium percarbonate (SPC). Two methods of production, chemical reduction (CR) and solvo-thermal (ST), were tested for preparation of single (Fe) and binary (Fe-Cu) nanocomposites supported by reduced graphene oxide (rGO). A variety of analytical techniques including N2 adsorption Brunauer-Emmett-Teller (BET), x-ray diffraction (XRD), fourier-transfrom infrared spectroscopy (FTIR), and transmisison electron microscopy (TEM) were applied to characterize the physicochemical and microstructural properties of the synthesized nanocomposites. The characterization indicated that the CR method produced nanocomposites that comprised only mesoporous structure. Conversely, both micro and mesoporous structures were present for samples produced with the ST method. The synthesized single and bimetallic composites produced from the ST method showed higher surface areas, i.e. 93.6 m2/g and 119.2 m2/g as compared to the ones synthesized via the CR method, i.e. 13.8 m2/g and 38.0 m2/g respectively. The results of FTIR and XRD analyses confirmed that the ST method produced highly crystalline nanocomposites. SEM and TEM analysis validated that metallic particles with definite morphology well distributed on the surface of rGO. X-ray photoelectron spectroscopy (XPS) analysis confirmed the homogeneity nanocomposites and occurrence of variation in copper oxidation states during degradation process. EDS mapping validate the homogeneous distribution of Cu and Fe at reduced graphene oxide surface. The Fe-Cu/rGO (ST) activated SPC system effectively degraded TCA (92%) in 2.5 h at low nanocomposite dose compared to the Fe-Cu/rGO (CR) and only Fe, for which the maximum degradation efficiencies achieved were 81% and 34%. In conclusion, excellent catalytic characteristics were observed for the ST-synthesized single and bimetallic (Fe/rGO, Fe-Cu/rGO) catalysts. These catalysts were successful in improving the degradation of TCA via activated SPC.
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| 4. |
- Huang, X., et al.
(författare)
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Depth optimization of solidification properties of a latent heat energy storage unit under constant rotation mechanism
- 2023
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Ingår i: Energy and Buildings. - : Elsevier Ltd. - 0378-7788 .- 1872-6178. ; 290
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Tidskriftsartikel (refereegranskat)abstract
- Latent heat storage technology plays an important role in the effective utilization of clean energy such as solar energy in building heating, but the low thermal conductivity of heat storage medium (phase change material) affects its large-scale application. As a new heat storage enhancement technology, rotation mechanism has a good application prospect. In this paper, the solidification performance of a triplex-tube latent heat thermal energy storage unit at constant speed (0.5 rpm) is studied numerically. Different optimization design methods (Taguchi method and response surface method) are used for deep analysis. The influences of fin position, number, and material on solidification properties are explored by the Taguchi method. Then, the unit structure (fin angle, fin length, and fin width) is optimized by the response surface method. Compared with the original structure, the average heat release rate of 8 copper fins with all outer tubes is increased by 108.93%, and the solidification time is reduced by 52.06%. The optimal structure can further shorten the solidification time by 29.14% and increase the average heat release rate by 40.5%. Additionally, the study of wall temperature shows that increasing temperature difference makes solidification speed faster and heat energy release faster. This effect effectively eliminates the adverse effects of slow solidification during the later stages of the process on the system.
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| 5. |
- Lu, L., et al.
(författare)
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Refinement and predicting formaldehyde concentrations of indoor fabric : Effects of temperature and humidity
- 2023
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Ingår i: Chemosphere. - : Elsevier Ltd. - 0045-6535 .- 1879-1298. ; 342
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Tidskriftsartikel (refereegranskat)abstract
- Indoor air pollution resulting from volatile organic compounds (VOCs) is a significant health concern, especially formaldehyde. Therefore, predicting indoor formaldehyde concentration is essential for environmental control. In this research, the authors develop a thermal and wet coupling calculation model of porous fabric that considers the influence of different phases of wet components and the coupling effect of heat and humidity on formaldehyde migration. We propose a modified calculation method of the formaldehyde mass transfer characteristic parameters of fabric to obtain the diffusion coefficient D and partition coefficient K. The heat and humidity coupling model and formaldehyde mass transfer model of fabric are simultaneously solved, and the authors analyze the influence mechanism of fabric loading rate, fabric type, temperature, and humidity on indoor formaldehyde mass transfer characteristics. We study the variation trend of fabric formaldehyde mass transfer characteristics coefficient and the temporal and spatial distribution of indoor formaldehyde concentration. The theoretical model is applied to practical problems by pre-evaluating the indoor formaldehyde concentration of decorated residential buildings in typical climate areas of China before occupancy. The authors obtain the variation rule of indoor formaldehyde concentration of residential buildings under typical hot and humid climate conditions, building materials, furniture, and fabrics. To provide theoretical support for indoor environmental control and human health protection.
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| 6. |
- Yang, Xiaohu, et al.
(författare)
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Comparison of direct numerical simulation with volume-averaged method on composite phase change materials for thermal energy storage
- 2018
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 229, s. 700-714
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Tidskriftsartikel (refereegranskat)abstract
- Melting heat transfer in open-cell metal foams embedded in phase-change materials (PCMS) predicted by the volume-averaged method (VAM) was systematically compared with that calculated using direct numerical simulation (DNS), with particular attention placed upon the contribution of natural convection in the melt region to overall phase change heat transfer. The two-temperature model based on the assumption of local thermal non-equilibrium was employed to account for the large difference of thermal conductivity between metallic ligaments and PCM (paraffin). The Forchheimer extended Darcy model was employed to describe the additional flow resistance induced by metal foam. For the DNS, a geometric model of metal foam based on tetrakaidehedron cells was reconstructed. The DNS results demonstrated significant temperature difference between ligament surface and PCM, thus confirming the feasibility of local thermal non-equilibrium employed in VAM simulations. Relative to the DNS results, the VAM combined with the two-temperature model could satisfactorily predict transient solid-liquid interface evolution and local temperature distribution, although pore-scale features of phase change were lost. The presence of natural convection affected significantly the melting front shape, temperature distribution and full melting. The contribution of natural convection to overall phase change heat transfer should be qualitatively and quantitatively given sufficient consideration from both macroscopic (VAM) and microscopic (DNS) point of views. Besides, practical significance and economic prospective using metal foam in TES unit for WHR system to provide residential heating or hot water is discussed and analyzed.
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| 7. |
- Yang, Xiaohu, et al.
(författare)
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Thermal performance of a shell-and-tube latent heat thermal energy storage unit : Role of annular fins
- 2017
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 202, s. 558-570
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Tidskriftsartikel (refereegranskat)abstract
- This study conducts numerical investigations on melting process in a shell-and-tube latent heat thermal energy storage (LHTES) unit with annular fins. Commercial grade paraffin is employed as the phase change material (PCM) and water serves as the heat transfer fluid (HTF). Finite-volume-method (FVM) based numerical simulations are performed to investigate the effects of fin number, height and thickness on the phase change process. Particular attention is made to justify the contribution of local natural convection to the overall phase change process. Results demonstrate that the full melting time could be maximally reduced by 65% by inserting annular fins into PCM. For maximizing thermal performance, an optimal group fin parameter (fin number N = 31, thickness t/l = 0.0248 and interval l/L = 0.0313) is recommended for the present study.
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| 8. |
- Zhang, Z., et al.
(författare)
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Carbon mitigation potential afforded by rooftop photovoltaic in China
- 2023
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Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Rooftop photovoltaics (RPVs) are crucial in achieving energy transition and climate goals, especially in cities with high building density and substantial energy consumption. Estimating RPV carbon mitigation potential at the city level of an entire large country is challenging given difficulties in assessing rooftop area. Here, using multi-source heterogeneous geospatial data and machine learning regression, we identify a total of 65,962 km2 rooftop area in 2020 for 354 Chinese cities, which represents 4 billion tons of carbon mitigation under ideal assumptions. Considering urban land expansion and power mix transformation, the potential remains at 3-4 billion tons in 2030, when China plans to reach its carbon peak. However, most cities have exploited less than 1% of their potential. We provide analysis of geographical endowment to better support future practice. Our study provides critical insights for targeted RPV development in China and can serve as a foundation for similar work in other countries.
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