| 1. |
- Li, Xueqiang, et al.
(författare)
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Energy storage systems for refrigerated warehouses
- 2017
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Ingår i: Leveraging Energy Technologies and Policy Options for Low Carbon Cities. - : Elsevier. ; 143, s. 94-99
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Konferensbidrag (refereegranskat)abstract
- To reduce the peak load, dynamic electricity price schemes have been widely used. Refrigerated warehouses consume a large amount of energy, most of which happens during the daytime due to the higher ambient temperature. This work evaluated the potential benefits of integrating energy storage in the refrigerated warehouses. Two types of energy storage systems have been considered, including a cold energy storage system and an electrical energy storage system. A dynamic model has been developed in TRNSYS to study the performance of those two energy storage systems and assess the benefits. Results show that using the cold energy storage to shift power consumption from daytime to nighttime can increase the energy efficiency of the refrigeration system. However, as the electrical energy storage system can shift more power consumption, it can achieve a large cost saving. Compared to the reference system without energy storage, the introductions of a cold energy storage system and an electrical energy storage system can reduce the operational cost by 10 and 53.7% respectively.
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| 2. |
- Li, Xueqiang, et al.
(författare)
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Key factors affecting the performance of the multi-stream heat exchanger for CO2 condensation
- 2023
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Ingår i: International journal of thermal sciences. - : Elsevier Masson s.r.l.. - 1290-0729 .- 1778-4166. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- The multi-stream heat exchanger (MS-HEX) is an important equipment in CO2 capture processes, especially for CO2 condensation. By now, little attention has been paid to thoroughly investigating its performance. To provide insights for optimizing the design and operation of the MS-HEX, this paper evaluated the impacts of some key factors, such as the flow arrangement and the content of non-condensable (NC) gases, on the performances of the MS-HEX, including the exit vapor fraction, the pressure drop, the heat transfer coefficient (HTC), and the sub-cooling degree. A 3D CFD model was developed and validated. Based on simulations, it was found that the flow arrangement can clearly affect the performance of the MS-HEX, and there existed an optimal one, which can give the highest sub-cooling degree. Moreover, increasing the volume fraction of NC gases can lead to a decrease of the HTC and the sub-cooling degree; and Ar showed the biggest impact, followed by O2 and N2. For instance, compared to condensing a stream containing 5 vol % N2, condensing a stream containing 5 vol % Ar led to a lower HTC and a lower sub-cooling degree, which can be up to 27.3% and 4 K, respectively.
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| 3. |
- Li, Xueqiang, et al.
(författare)
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Optimizing cooling electronic chips at high altitude with consideration of solar radiation
- 2023
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Ingår i: International journal of thermal sciences. - : Elsevier. - 1290-0729 .- 1778-4166. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining a proper working environment for electronic chips is challenging for airships, as the ambient parameters at high altitude are largely different from those on the ground, which can influence the performance of cooling. This work aims to optimize the finned sink to minimize the weight with the consideration of the impact of solar radiation. By using a validated 3D model, it was found that the ignorance of the solar radiation can lead to a temperature deviation of 4.1 °C for electronic chips at 20 km when the solar radiation intensity was 1400 W/m2 and the wind speed was 10 m/s. Meanwhile, compared to the solar radiation intensity and the emissivity, the direction of solar radiation showed more impacts. In addition, even though the solar radiation doesn't influence the optimal fin height, fin number, and fin thickness, it would clearly affect the optimal heat transfer area ratio. As a result, it can clearly change the optimized weight, which was 5.7% higher if the solar radiation was not considered. © 2022 The Authors
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| 4. |
- Li, Xueqiang, et al.
(författare)
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Toxicity of ionic liquid on anaerobic digestion
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; 142, s. 938-942
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion is a straightforward process to produce energy from biomass. However, the lignin composed of phenylpropanoid units induces a strong resistance for the hydrolysis step. Ionic liquids (ILs) have been applied in biomass pretreatment to dissolve the biomass components and enhance the anaerobic digestion. However, there are still some challenges such as the toxicity. ILs could inhibit the digestion process and reduce the CH4 production. In this work, a toxicity test for [BMIM]Cl (1-chlorobutane and N-methylimidazole) was conducted. Results show that IL has a strong inhibition and lowered CH4 production when its concentration was higher. At 0.2305±0.0116 g L-1 and 0.4367±0.0219 g L-1, the anaerobic digestion process was inhibited by 10 and 50%, respectively. Accordingly, a higher recovery ratio or a lower pretreatment ratio are necessary to avoid the negative impact of inhibition on BMP.
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| 5. |
- Zhang, Pan, et al.
(författare)
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Photochemical H-2 production with noble-metal-free molecular devices comprising a porphyrin photosensitizer and a cobaloxime catalyst
- 2010
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 46:46, s. 8806-8808
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Tidskriftsartikel (refereegranskat)abstract
- Among three noble-metal-free molecular devices (1-3) containing a porphyrin photosensitizer and a cobaloxime catalyst, the one with a zinc porphyrin unit displayed apparently higher efficiency for photoinduced H-2 production than complex 2 with a magnesium porphyrin and 3 with a free-base porphyrin, possibly due to the formation of a TEA center dot center dot center dot ZnPor-Co triad in solution.
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| 6. |
- Zhu, K., et al.
(författare)
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Experimental and theoretical study of a novel loop heat pipe
- 2018
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Ingår i: Applied Thermal Engineering. - : Elsevier Ltd. - 1359-4311 .- 1873-5606. ; 130, s. 354-362
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Tidskriftsartikel (refereegranskat)abstract
- In order to reduce the heat leakage from the evaporator and achieve a longer transport distance, a new type of loop heat pipe (LHP) has been proposed based on a hypothesis that the circulation of working fluids is driven by not only the capillary head, but also the pressure head due to evaporation. In the evaporator, the wick is separated from the heating surface by a chamber, which can effectively use the pressure head generated by evaporation. In this work, a prototype of such a LHP was studied experimentally and theoretically. In order to understand the mechanism of operation, a new mathematical model was established. Comparing the simulated results with the experimental data about the operation temperature, a good agreement was observed that the average absolute deviation and the maximum absolute deviation were in ranges of 0.67–1.21 °C and −1.3 to 6 °C, respectively. With the validated model, the two driving forces were investigated. Results showed that the ratio of the pressure head of evaporation to the capillary head was in a range of 59–54% corresponding to heating powers from 30 W to 110 W. It confirms that the pressure head due to evaporation plays an important role in the circulation of working fluids.
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| 7. |
- Zhu, Kai, et al.
(författare)
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Techno-economic feasibility of integrating energy storage systems in refrigerated warehouses
- 2018
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 216, s. 348-357
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Tidskriftsartikel (refereegranskat)abstract
- This work evaluates the techno-economic feasibility of integrating the cold energy storage system and the electrical energy storage system in a refrigerated warehouse for shifting the power consumption. A dynamic model has been developed in TRNSYS (R). Based on the dynamic simulation, the performance and benefit of those two types of energy storage systems were compared. Results showed that, the integration of a cold energy storage can reduce the electricity consumption and operational cost by 4.3% and 20.5%, respectively. Even though integrating a battery system will increase the electricity consumption by 3.9%, it can reduce the operational cost by 18.7%. The capacity of the energy storage systems, the battery price and the peak electricity price had been identified as key parameters affecting the performance and benefit. To achieve a payback period less than 3 year, for the integration of a cold energy storage system, the peak electricity price should be increased by 25% from the current level, while for the integration of a battery system, the battery price should drop to 0.7 kRMB/kWh.
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| 8. |
- Dong, Jingfeng, et al.
(författare)
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Promoting Effect of Electrostatic Interaction between a Cobalt Catalyst and a Xanthene Dye on Visible-Light-Driven Electron Transfer and Hydrogen Production
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:30, s. 15089-15096
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Tidskriftsartikel (refereegranskat)abstract
- The readily obtained noble-metal-free molecular catalyst systems, with xanthene dyes (Rose Bengal, RB(2-); Eosin Y, EY(2-); and Eosin B, EB(2-)) as photosensitizers, [Co(bpy)(3)]Cl(2) as catalyst, and triethylamine as sacrificial electron donor, are highly active for visible-light-driven (lambda > 450 nm) hydrogen production from water. The turnover frequency is up to 54 TON/min versus RB(2-) with a RB(2-)/[Co(bpy)(3)]Cl(2) molar ratio of 1:10 in CH(3)CN/H(2)O under optimal conditions in the first half hour of irradiation (lambda > 450 rim), and the turnover number is up to 2076 versus RB(2-). Comparative studies show the following: (1) The photocatalytic H(2)-evolving activity of the cationic cobalt complex [Co(bpy)(3)]Cl(2), is apparently higher than the neutral cobaloxime complexes with xanthene dyes as potosensitizers, and also much higher than the analogous system of [Ru(bpy)(3)]Cl(2)/[Co(bpy)(3)]Cl(2). (2) The UV-vis absorptions of xanthene dyes are red shifted to different extents upon addition of [Co(bpy)(3)]Cl(2) to the aqueous or CH(3)CN/H(2)O solutions of these dyes, while no change was observed in UV-vis absorptions of photosensitizer with addition of the cobaloximes to the aqueous solution of RB(2-) or addition of [Co(bpy)(3)]Cl(2) to the aqueous solution of [Ru(bpy)(3)]Cl(2). (3) The fluorescence of RB(2-) is significantly quenched by [Co(bpy)(3)]Cl(2), but not by the cobaloximes. These special performances of [Co(bpy)(3)]Cl(2) are attributed to the electrostatically attractive interaction between the anionic organic dyes and the cationic cobalt catalyst. The probable mechanism for photoinduced hydrogen production catalyzed by the system of RB(2-), [Co(bpy)(3)]Cl(2), and triethylamine is discussed in detail on the basis of fluorescence. fand transient absorption spectroscopic studies. "
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| 9. |
- Li, Xueqiang, et al.
(författare)
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Noncovalent assembly of a metalloporphyrin and an iron hydrogenase active-site model : Photo-induced electron transfer and hydrogen generation
- 2008
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207 .- 1089-5647. ; 112:27, s. 8198-8202
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Tidskriftsartikel (refereegranskat)abstract
- A noncovalent assembly of a pyridyl-functionalized hydrogenase active-site model complex and zinc tetraphenylporphyrin has been obtained and characterized. Upon light irradiation, fluorescence quenching by electron transfer was observed from the singlet excited state of the porphyrin to the diiron center, and the mechanism was verified by fluorescence lifetime and transient absorption spectroscopic measurements. In contrast to molecular dyads linked by covalent bonds, the assembled system was designed to avoid charge recombination via complex dissociation after photo-induced electron transfer. Visible light-driven hydrogen generation was observed from this self-assembled system. The assembling strategy employed in this study has the potential to be used for any other hydrogenase models in the future.
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| 10. |
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| 11. |
- Li, Xueqiang, et al.
(författare)
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Photocatalytic Water Reduction and Study of the Formation of FeIFe0 Species in Diiron Catalyst Sytems
- 2012
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631. ; 5:5, s. 913-919
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Tidskriftsartikel (refereegranskat)abstract
- Noble-metal-free systems with bio-inspired diiron dithiolate mimics of the [FeFe]-hydrogenase active site, namely, [(mu-pdt)Fe2(CO)5L] [pdt=propanedithiolate; L=P(CH2OH)3 (1), P(CH3)3 (2)], as water reduction catalysts with xanthene dyes as photosensitizers and triethylamine as a sacrificial electron donor were studied for visible-light-driven water reduction to hydrogen. These systems display good catalytic activities with the efficiencies in hydrogen evolution of up to 226 turnovers for 1, if Eosin Y was used as the photosensitizer in an environmentally benign solvent (EtOH/H2O) after 15 h of irradiation (?>450 nm) under optimal conditions. Under all of the conditions adopted, 1 that has a water soluble phosphine ligand, P(CH2OH)3 displayed a higher efficiency than 2, which bears a PMe3 ligand. The photoinduced electron transfer in the systems was studied using fluorescence, transient absorption, time-resolved UV/Vis, and in situ electron paramagnetic resonance (EPR) spectroscopy. A new electron-transfer mechanism is proposed for hydrogen evolution by these iron-based photocatalytic systems.
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| 12. |
- Shengchun, L., et al.
(författare)
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Experimental investigation on drying performance of an existed enclosed fixed frequency air source heat pump drying system
- 2018
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Ingår i: Applied Thermal Engineering. - : Elsevier Ltd. - 1359-4311 .- 1873-5606. ; 130, s. 735-744
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Tidskriftsartikel (refereegranskat)abstract
- As the quick development of industry drying technology, different heat pump drying systems were proposed in recent decades. Enclosed heat pump drying system was considered as the most widely used system. For an existed enclosed fixed frequency heat pump drying system, drying time could be decreased by increasing air temperature at inlet of drying chamber. However, as a fundamental problem, system drying performance influenced by air flow ratio was not tested and reported in open literatures. Therefore, basing on adding an air bypass duct, drying performance of an enclosed system was experimental investigated in this study, with 15 mm thickness fresh carrot chips used. Furthermore, qualitatively and quantitatively comparisons and discussions on experimental results were conducted. A whole drying process were firstly divided into three stages by different water content ratios, preheating stage at 98–100%, fast drying stage at 20–98%, and later drying stage at 0–20%, respectively. For the inlet air temperature of drying chamber is fixed at 40 °C, material drying time for water content ratio reaching 20% could be effectively decreased as much as 42 min, or 15.0%, by the strategy of hot air bypassed. After the drying time shortened, the calculated energy consumption for compressor was also decreased from 4.27 kWh for AFR at 1.0 to 3.63 kWh for AFR at 0.6. Contributions of this study can guide low temperature material drying process. Clearly, system control optimization and energy saving were both expected.
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| 13. |
- Wang, Mei, et al.
(författare)
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Approaches to efficient molecular catalyst systems for photochemical H(2) production using [FeFe]-hydrogenase active site mimics
- 2011
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40:48, s. 12793-12800
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Tidskriftsartikel (refereegranskat)abstract
- The research on structural and functional biomimics of the active site of [FeFe]-hydrogenases is in an attempt to elucidate the mechanisms of H(2)-evolution and uptake at the [FeFe]-hydrogenase active site, and to learn from Nature how to create highly efficient H(2)-production catalyst systems. Undoubtedly, it is a challenging, arduous, and long-term work. In this perspective, the progresses in approaches to photochemical H(2) production using mimics of the [FeFe]-hydrogenase active site as catalysts in the last three years are reviewed, with emphasis on adjustment of the redox potentials and hydrophilicity of the [FeFe]-hydrogenase active site mimics to make them efficient catalysts for H(2) production. With gradually increasing understanding of the chemistry of the [FeFe]-hydrogenases and their mimics, more bio-inspired proton reduction catalysts with significantly improved efficiency of H(2) production will be realized in the future.
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| 14. |
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| 15. |
- Zhang, Pan, et al.
(författare)
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Photocatalytic Hydrogen Production from Water by Noble-Metal-Free Molecular Catalyst Systems Containing Rose Bengal and the Cobaloximes of BFx-Bridged Oxime Ligands
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:37, s. 15868-15874
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen evolution was observed from the noble-metal-free catalyst systems, comprising Rose Bengal, BFx-bridged cobaloximes, and triethylamine, in an aqueous solution under irradiation of visible light. Two types of BFx-bridged cobaloximes namely, the annulated cobaloximes [Co(dmgBF(2))(2)(H2O)(2)] (1, dmgBF(2) = (difluoroboryl)dimethylglyoximate anion) and [Co(dpgBF(2))(2)(H2O)(2)] (2, dpgBF(2) =(difluoroboryl)diphenylglyoximate anion), and the clathrochelated cobaloximes [Co(dmg(BF)(2/3))(3)](BF4) (3) and [Co(dpg(BF)(2/3))(3)](BF4) (4)-were used as catalysts. Among the four cobalt complexes, complex 1 displayed the highest hydrogen-evolving efficiency, with turnovers up to 327. Complexes 2 and 4 that bear the diphenylglyoximate ligands exhibited much lower efficiencies as compared with their analogues 1 and 3 that have the dimethylglyoximate ligands. The hydrogen-evolving efficiency of the annulated cobalt(II) complex 1 that contains two labile axial ligands is more than three times as high as that of the encapsulated cobalt(III) complex 3 that has a single macrobicyclic ligand. The different pathways for formation of the cobalt(I) species from these two types of cobaloximes are discussed on the basis of the results obtained from fluorescence and laser flash photolysis spectroscopic studies.
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| 16. |
- Zhang, Pan, et al.
(författare)
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Photochemical hydrogen production with molecular devices comprising a zinc porphyrin and a cobaloxime catalyst
- 2012
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Ingår i: Science China Chemistry. - : Springer Science and Business Media LLC. - 1674-7291 .- 1869-1870. ; 55:7, s. 1274-1282
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Tidskriftsartikel (refereegranskat)abstract
- Two new noble-metal-free molecular devices, [{Co(dmgH)(2)Cl}{Zn(PyTPP)}] (1, dmgH = dimethyloxime, PyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) and [{Co(dmgH)(2)Cl}{Zn(apPyTPP)}] (2, apPyTPP = 5-[4-(isonicotinamidyl)phenyl]-10,15,20-triphenylporphyrin), for light-driven hydrogen generation were prepared and spectroscopically characterized. The zinc porphyrin photosensitizer and the Co-III-based catalyst unit are linked by axial coordination of a pyridyl group in the periphery of zinc-porphyrin to the cobalt centre of catalyst with different lengths of bridges. The apparent fluorescence quenching and lifetime decays of 1 and 2 were observed in comparison with their reference chromophores, Zn(PyTPP) (3) and Zn(apPyTPP) (4), suggesting a possibility for an intramolecular electron transfer from the singlet excited state of zinc porphyrin unit to the cobalt centre in the molecular devices. Photochemical H-2-evolving studies show that complexes 1 and 2 are efficient molecular photocatalysts for visible light-driven H-2 generation from water with triethylamine as a sacrificial electron donor in THF/H2O, with turnover numbers up to 46 and 35 for 1 and 2, respectively. In contrast to these molecular devices, the multicomponent catalyst of zinc porphyrin and [Co(dmgH)(2)PyCl] did not show any fluorescence quenching and as a consequence, no H-2 gas was detected by GC analysis in the presence of triethylamine with irradiation of visible light. The plausible mechanism for the photochemical H-2 generation with these molecular devices is discussed.
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