| 1. |
- Li, Shian, et al.
(författare)
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Analysis of heat and mass transport characteristics in microchannel reactors with non-uniform catalyst distributions for hydrogen production
- 2022
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 32:10, s. 3191-3209
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to investigate the heat and mass transport characteristics in microchannel reactors with non-uniform catalyst distributions. Design/methodology/approach: A two-dimensional model is developed to study the heat and mass transport characteristics in microchannel reactors. The heat and mass transport processes in the microchannel reactors with non-uniform catalyst distribution in the catalytic combustion channel are also studied. Findings: The simulated results are compared in terms of the distributions of species mole fraction, temperature and reaction rate for the conventional and new designed reactors. It is found that the chemical reaction, heat and mass transport processes are significantly affected and the maximum temperature in the reactor is also greatly reduced when a non-uniform catalyst distribution is applied in the combustion catalyst layer. Practical implications: This study can improve the understanding of the transportation characteristics in microchannel reactors with non-uniform catalyst distributions and provide guidance for the design of microchannel reactors. Originality/value: The design of microchannel reactors with non-uniform catalyst distributions can be used in methane steam reforming to reduce the maximum temperature inside the reactor.
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| 2. |
- Li, Shian, et al.
(författare)
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Performance improvement of proton exchange membrane fuel cells with wavy flow channels : An experimental study
- 2022
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 46:13, s. 18511-18517
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Tidskriftsartikel (refereegranskat)abstract
- The gas flow field design plays a vital role in the cell performance of proton exchange membrane fuel cells, especially at high current densities. In this study, wavy flow channels are designed and adopted on the cathode side to enhance the mass transport process. Results demonstrate that the wavy flow channels proposed in this paper significantly improve cell performance at high current densities. The power density is improved from 0.121 to 0.314 W/cm2 at the maximum current density used in this present study. Effects of operating temperature (333.15, 343.15 and 353.15 K), humidification temperature (313.15, 333.15 and 353.15 K), anode volumetric flow rate (0.4, 0.5 and 0.6 L/min), and cathode volumetric flow rate (1.0, 1.5 and 2.0 L/min) on the performance of fuel cells with the novel wavy flow channels are deeply studied. In addition, the influence of the amplitude (0.3, 0.5 and 0.7 mm) and number (5, 7 and 9) of the wavy configurations on performance are illustrated and compared in detail. Furthermore, fuel cells with gradient wavy channels are also designed and experimentally investigated.
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| 3. |
- Yang, Chao, et al.
(författare)
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Computational fluid dynamics model development on transport phenomena coupling with reactions in intermediate temperature solid oxide fuel cells
- 2013
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- A 3D model is developed to describe an anode-supported planar solid oxide fuel cell (SOFC), by ANSYS/Fluent evaluating reactions including methane steam reforming (MSR)/water-gas shift (WGSR) reactions in thick anode layer and H-2-O-2/CO-O-2 electrochemical reactions in anode active layer, coupled with heat, mass species, momentum, and ion/electron charges transport processes in SOFC. The predicted results indicate that electron/ion exchange appears in the very thin region in active layers (0.018 mm in anode and 0.01 mm in cathode), based on three phase boundary, operating temperature and concentration of reactants (mainly H-2). Active polarization happening in active layers dominates over concentration and ohmic losses. High gradient of current density exists near interface between electrode and solid conductor due to the block by gas channel. It is also found the reaction rates of MSR and WGSR along main flow direction and cell thickness direction decrease due to low concentration of fuel (CH4) caused by mass consumption. With increasing operating temperature from 978 K to 1088 K, the current density and the reaction rate of MSR are increased by 10.8% and 5.4%, respectively. While ion current density is 52.9% higher than in standard case, and H-2 is consumed by 5.1% more when ion conductivity is doubled. CO-O-2 has been considered in charge transfer reaction in anode active layer and it is found that the current density and species distributions are not sensitive, but WGSR reaction will be forced backwards to supply more CO for CO-O-2 electrochemical reaction. (V) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4798789]
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| 4. |
- Li, Shian, et al.
(författare)
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Numerical investigation on the impact of membrane thickness on transport phenomena in PEM fuel cells
- 2020
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Ingår i: International Journal of Electrochemical Science. - : Elsevier BV. - 1452-3981. ; 15, s. 4138-4147
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional mathematical model is used to investigate the performance and transport characteristics of PEM fuel cells with different membrane thicknesses. The overall cell performance of three cases are presented and compared. In addition, the local temperature, liquid water saturation, water content and current density distributions are analyzed and compared. Results show that performance increases with decreasing membrane thickness and the local transport characteristics is also significantly affected. The ohmic loss is mainly caused by the proton transport process inside fuel cell. And a thinner membrane can enhance water back diffusion process in the membrane which is beneficial to the water management at the anode side.
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| 5. |
- Li, Shian, et al.
(författare)
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Numerical study on thermal performance of cold plates with leaf type channels for lithium-ion batteries
- 2023
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 33:10, s. 3519-3534
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this study is to design a new type of cold plate to improve the thermal performance of liquid-cooled thermal management system of lithium-ion batteries. Design/methodology/approach: A cold plate with leaf type channels is proposed to enhance the cooling performance. Effects of the leaf type channel parameters (i.e. channel angle 20°, 40°, 60°, 80°; coolant mass flow rate 0.25 × 10–3, 0.50 × 10–3, 0.75 × 10–3, 1.00 × 10–3, 1.25 × 10–3 kg·s−1; channel number 1, 3, 5, 7) on the performance are numerically investigated by using a 3D mathematical model. Findings: Compared to the traditional I type channels, the leaf type channels have better cooling performance. It is found that the battery temperature variation and channel pressure drop are decreased with decreasing channel angle and increasing channel number. In addition, the cooling performance can be improved by increasing the coolant mass flow rate. Practical implications: This study can provide guidance for the development of novel effective cold plates. Originality/value: The design of cold plates with leaf type channels can be used in liquid-cooled thermal management system to reduce the battery temperature difference.
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| 6. |
- Li, Shian, et al.
(författare)
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Performance and transport characteristics of solid oxide fuel cells with counter flow arrangement
- 2020
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Ingår i: International Journal of Electrochemical Science. - : Elsevier BV. - 1452-3981. ; 15:2, s. 1338-1346
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a two-dimensional model including the governing equations of mass, momentum, species, energy and charge, is developed and then applied to investigate the performance and multiphysics transport processes of solid oxide fuel cells with counter-flow arrangement. The current density and power density are calculated and presented, and the distributions of species and temperature are also analyzed. In addition, temperature distributions of fuel cells with varying operating temperature, anode inlet flow velocity and cathode inlet flow velocity are demonstrated. The results show that the temperature gradient increases with increasing operating temperature. And the local temperature decreases with increasing inlet flow velocities, especially the increasing cathode inlet flow velocity.
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| 7. |
- Shao, Zicheng, et al.
(författare)
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Effect of Sr Substitution on the Novel la 1-xSr xCo0.5Ni0.5O3- δPerovskite-Type Catalysts for Hydrogen Production in Ethanol Steam Reforming
- 2023
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 2023
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Tidskriftsartikel (refereegranskat)abstract
- La1-xSrxCo0.5Ni0.5O3-δ perovskites with different substitution of La by Sr have been firstly synthesized and applied as catalysts for ethanol steam reforming (ESR). The effect of partial Sr substitution on the performance and stability of La1-xSrxCo0.5Ni0.5O3-δ for ESR was investigated. The synthesized samples were characterized by XRD, SEM, BET, and EDS techniques. The results show that with the increase of substitution of La by Sr, the pore size and surface area of La1-xSrxCo0.5Ni0.5O3-δ perovskite increase. The doping of Sr causes changes in the specific surface area, pore volume, and pore size of the catalyst, which in turn causes changes in its catalytic activity. Meanwhile, La0.1Sr0.9Co0.5Ni0.5O3-δ with a highest SBET presents the highest ethanol conversion rate among all the samples. The modifications of catalyst characteristics caused by the Sr substitution in La1-xSrxCo0.5Ni0.5O3-δ directly affect its catalytic performance in the ESR. What is more, the influences of operating parameters on the catalytic activity of La0.1Sr0.9Co0.5Ni0.5O3-δ were studied in detail, and the optimum conditions were determined and applied for stability experiments. When the temperature is lower than 500°C, the selectivity of gas products is most likely affected by the dehydrogenation of ethanol and the decomposition of acetaldehyde. Meanwhile, the improving hydrogen selectivity and reducing the formation of by-products can be achieved by increasing the reaction temperature. The best catalytic performance for hydrogen production was achieved with La0.1Sr0.9Co0.5Ni0.5O3-δ which presented the highest ethanol conversion (98.7%) under the optimal reaction conditions. La0.1Sr0.9Co0.5Ni0.5O3-δ perovskites with higher strontium degree of substitution exhibited an excellent activity and stability of the catalysts derived.
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| 8. |
- Shen, Qiuwan, et al.
(författare)
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Analysis of heat and mass transport characteristics in anode-supported solid oxide fuel cells at various operating conditions
- 2019
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Ingår i: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 75:8, s. 509-522
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the heat and mass transport characteristics of anode-supported solid oxide fuel cells (SOFCs) are numerically investigated by using a two-dimensional model. The mathematical model is validated by comparing the numerical results with experimental data found in the open literature. The species and temperature distributions of SOFCs at different cell voltages are presented and compared. Effects of operating temperature, flow direction arrangement, and flow velocity on the overall cell performance and local temperature distribution are also analyzed. It is concluded that the local temperature is increased with decreasing operating cell voltage, increasing operating temperature, and decreasing cathode flow velocity. The temperature distribution is significantly changed when counter-flow arrangement is used instead of coflow arrangement. In addition, the effect of anode flow velocity on temperature distribution is negligible.
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| 9. |
- Shen, Qiuwan, et al.
(författare)
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Effect of A-/B-site doping on oxygen non-stoichiometry, structure characteristics, and O2 releasing behavior of La1−xCaxCo1−yFeyO3−δ perovskites
- 2019
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Oxy-fuel combustion is one of the proposed technologies with the potential to achieve zero CO2 emission. La1−xCaxCo1−yFeyO3−δ (LCCF) perovskites are promising materials with high selectively for oxygen. In this study, the oxygen non-stoichiometry of perovskites LCCF was investigated by means of iodometric titration. LCCF was prepared using the liquid citrate method, and the phase structures were identified by X-ray diffraction. Fixed-bed experiments were performed to study the oxygen desorption performance of LCCF. The oxygen deficiency of LCCF increased with increasing Ca molar content of A site, but the value of δ of LCCF with increasing Fe molar content in B site is nearly constant. Experimental observation demonstrated that the O2 release amount of LCCF does not depend on oxygen non-stoichiometry δ generated from A-site doping. At the same time, doping Fe in B site has an obvious impact on the oxygen desorption amount.
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| 10. |
- Shen, Qiuwan, et al.
(författare)
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Effects of B-site Al doping on microstructure characteristics and hydrogen production performance of novel LaNixAl1-xO3-δ perovskite in methanol steam reforming
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 268
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Tidskriftsartikel (refereegranskat)abstract
- A series of B-site aluminum doped LaNixAl1-xO3-δ (x = 0–1) perovskite samples were prepared by the sol-gel method and applied as catalysts for methanol steam reforming (MSR). The synthesized perovskite catalysts were characterized by SEM, XRD, SEM-EDS, XPS, TEM and BET. Results showed that LaNi0.4Al0.6O3-δ exhibited the highest methanol conversion and hydrogen production amount per unit time. However, the excessive aluminum content led to a decrease in H2 selectivity, and the high W/M promoted the reverse water-gas shift reaction (RWGS), which resulted in a decrease in CO selectivity and an increase in CO2 selectivity. The results of XRD, XPS and BET indicated that the LaNi0.4Al0.6O3-δ catalyst sample still exhibit a very typical perovskite structure after hydrogen reduction treatment. The results also indicated that there were active sites for MSR on the LaNi0.4Al0.6O3-δ sample that were not successfully reduced, but the specific surface area and porous characteristics of the catalyst were changed by H2 reduction treatment. The optimal reaction temperature, GHSV and W/M were determined to be 600 °C, 10,520 h−1, 3:1, respectively. In addition, the LaNi0.4Al0.6O3-δ shows high catalytic activity within 20 h of stability test. The average methanol conversion and H2 selectivity during 20 h were 91% and 93% on average, respectively.
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