| 1. |
- Li, Hailong, 1976-, et al.
(författare)
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A new modification on RK EOS for gaseous CO2 and gaseous mixtures of CO2 and H2O
- 2006
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 30:3, s. 135-148
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Tidskriftsartikel (refereegranskat)abstract
- To develop an equation of state with simple structure and reasonable accuracy for engineering application, Redlich-Kwong equation of state was modified for gaseous CO2 and CO2-H2O mixtures. In the new modification, parameter 'a' of gaseous CO2 was regressed as a function of temperature and pressure from recent reliable experimental data in the range: 220-750 K and 0.1-400 MPa. Moreover, a new mixing rule was proposed for gaseous CO2-H2O mixtures. To verify the accuracy of the new modification, densities were calculated and compared with experimental data. The average error is 1.68% for gaseous CO2 and 0.93% for gaseous mixtures of CO2 and H2O, Other thermodynamic properties, such as enthalpy and heat capacities of CO2 and excess enthalpy of gaseous CO2-H2O mixtures, were also calculated; results fit experimental data well, except for the critical region.
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| 2. |
- He, Xiaohe, et al.
(författare)
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Real-time regulation of room temperature based on individual thermal sensation using an online brain–computer interface
- 2022
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Ingår i: Indoor Air. - : NLM (Medline). - 0905-6947 .- 1600-0668. ; 32:e13106
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Tidskriftsartikel (refereegranskat)abstract
- Regulation of indoor temperature based on neurophysiological and psychological signals is one of the most promising technologies for intelligent buildings. In this study, we developed a system for closed-loop control of indoor temperature based on brain-computer interface (BCI) technology for the first time. Electroencephalogram (EEG) signals were collected from subjects for two room temperature categories (cool comfortable and hot uncomfortable) and used to build a thermal-sensation discrimination model (TSDM) with an ensemble learning method. Then, an online BCI system was developed based on the TSDM. In the online room temperature control experiment, when the TSDM detected that the subjects felt hot and uncomfortable, BCI would automatically turn on the air conditioner, and when the TSDM detected that the subjects felt cool and comfortable, BCI would automatically turn off the air conditioner. The results of online experiments in a hot environment showed that a BCI could significantly improve the thermal comfort of subjects (the subjective thermal comfort score decreased from 2.45 (hot uncomfortable) to 0.55 (cool comfortable), p < 0.001). A parallel experiment further showed that if the subjects wore thicker clothes during the experiment, the BCI would turn on the air conditioner for a longer time to ensure the thermal comfort of the subjects. This has further confirmed the effectiveness of TSDM model in evaluating thermal sensation under the dynamic change of room temperature and showed the model's good robustness. This study proposed a new paradigm of human-building interaction, which is expected to play a promising role in the development of human-centered intelligent buildings.
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| 3. |
- Dong, X., et al.
(författare)
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A novel design of a metal hydride reactor integrated with phase change material for H2 storage
- 2024
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 367
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Tidskriftsartikel (refereegranskat)abstract
- Using metal hydride for hydrogen storage in stationary applications and for transportation is a promising technology due to its advantages of large hydrogen storage capacity, low pressure and low energy consumption. Combining the metal hydride reactor with PCM is expected to recover the heat generated during the hydrogen absorption and use it for hydrogen desorption, thus improving the energy efficiency of the system. This paper proposes a metal hydride reactor integrated with honeycomb fins and PCM to enhance heat transfer. Based on simulations, the results show that the achieved hydrogen storage capacity is 1.326 wt%, the gravimetric and volumetric storage densities are 0.411% and 14.76 kg of H2 per m3, respectively, and the mean saturated rates are 1.222 × 10−3 g s−1 and 0.773 × 10−3 g s−1 for absorption and desorption processes. Compared with the reactor without fins, the mass and volume of the reactor using honeycomb fins are increased, resulting in a decrease in gravimetric and volumetric storage density, but a increase in reaction rate during hydrogen absorption and desorption processes. Based on this structure, we also propose a honeycomb fin reactor filled with sandwich PCM to further accelerate the heat transfer in the reaction process. Compare to the reactor with PCM only filled on the periphery of the honeycomb fins, the hydrogen absorption and desorption times are shortened by about 86.4% and 81.1%, respectively. In addition, different reactor structures are compared using multiple KPIs to provide relevant suggestions for the reactor optimization. The obtained research results can provide a reference for effective thermal management methods in MH storage systems.
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| 4. |
- Lu, F., et al.
(författare)
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Experimental study on thermal performance of transcritical CO 2 air source heat pump for space heating
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 5913-5919
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Konferensbidrag (refereegranskat)abstract
- Employing transcritical CO 2 heat pump system for space heating is an effective way to solve the issue of air pollution during the heating season in China. Thus, an experimental setup is developed to study the thermal performance of the transcritical CO 2 air source heat pump system used for space heating. The test results show that a maximum coefficient of performance (COP) of 2.88 is obtained at the optimum discharge pressure and the ambient temperature of 10 o C. The optimal high pressure is nearly a constant with the value of about 8.5 MPa for the ambient temperature in the range of -15~10 o C. The system COP increases with the ambient temperature increasing, and the outlet temperature of the gas cooler is a dominant influencing factor on the thermal performance of the heat pump system. Little difference can be found between the gas cooler outlet temperatures with the variation in ambient temperatures.
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| 5. |
- Nian, V., et al.
(författare)
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A feasibility study on integrating large-scale battery energy storage systems with combined cycle power generation – Setting the bottom line
- 2019
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 185, s. 396-408
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Tidskriftsartikel (refereegranskat)abstract
- Strong attention has been given to the costs and benefits of integrating battery energy storage systems (BESS) with intermittent renewable energy systems. What's neglected is the feasibility of integrating BESS into the existing fossil-dominated power generation system to achieve economic and environmental objectives. In response, a life cycle cost-benefit analysis method is introduced in this study taking into consideration three types of battery technologies, namely, vanadium redox flow battery, zinc bromine flow battery, and lithium-iron-phosphate battery. The objective is to evaluate the life cycle carbon emissions and cost of electricity production by combined cycle power generation with grid-connected BESS. Findings from the Singapore case study suggest a potential 3–5% reduction in the life cycle carbon emission factors which could translate to a cumulative carbon emission reduction of 9–16 million tonnes from 2018 to 2030 from electricity generation. Grid-connected BESS could reduce the levelized cost of electricity by 4–7%. A synergistic planning of CCGT and BESS could theoretically reduce the system level power generation capacity by 26% albeit a potential increase in the overall capital cost at the current cost of batteries. The projected battery cost reduction is critical in improving the feasibility of large-scale deployment.
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| 6. |
- Wei, P., et al.
(författare)
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Numerical study on thermal energy storage tube filled by metal foam with gradient porosities
- 2019
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- Thermal energy storage has attracted more and more attentions due mainly to its ability of peak load shifting. Shell-and-tube configuration is a typical heat exchanger for thermal energy storage. To enhance phase change heat transfer, open-cell metal foam has been involved in various kinds of shell-and-tube heat exchangers. To further improve the overall thermal performance of a shell-and-tube heat exchanger, metal foams with gradient porosities were inserted into the shell side. Positive and negative gradients in porosity were studied for comparison. Numerical model was developed based on the finite volume method and three sets of numerical simulations were performed. Transient melting front and melting fraction were illustrated for comparison. Results demonstrated that the positive gradient in porosity outperformed the other two kinds of configurations, resulting in a 17.5% reduction in full melting time.
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| 7. |
- Xiong, R., et al.
(författare)
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Key technologies for electric vehicles
- 2022
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Ingår i: Green Energy and Intelligent Transportation. - : Elsevier B.V.. - 2773-1537. ; 1:2
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Bai, Fan, et al.
(författare)
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Application of similarity theory in modeling the output characteristics of proton exchange membrane fuel cell
- 2021
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 46:74, s. 36940-36953
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Tidskriftsartikel (refereegranskat)abstract
- Proton Exchange Membrane Fuel Cell (PEMFC) has attracted widespread interest. In the present work, similarity analysis is adopted for a three-dimensional single-phase isothermal model of PEMFC to derive similarity criteria. Seven kinds of input criteria (Pi(1) similar to Pi(7)) are obtained, relevant to the fluid flow, pressure drop, flow resistance in a porous medium, activity loss, diffusion mass transfer, convective mass transfer and ohmic loss in PEMFC respectively. Dimensionless voltage and dimensionless current density are defined as two output criteria. Numerical verifications show that if the seven criteria keep their individual values with their components vary in a wide range, the dimensionless polarization curves keep the same with a deviation about 1%, showing the validity and feasibility of the present analysis. From the effect on the dimensionless polarization curve, sensibility analysis shows that the seven criteria can be divided into three categories: strong (Pi(4) and Pi(7), -94.9% similar to +349.2%), mild to minor (Pi(5) and Pi(6), -4.5% similar to +5.0%), and negligible (Pi(1), Pi(2) and Pi(3), -1.2% similar to +1.1%). The similarity analysis approach can greatly save computation time in modeling the output characteristics of PEMFC. (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
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| 9. |
- Bai, Q., et al.
(författare)
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Experimental investigation on the solidification behavior of phase change materials in open-cell metal foams
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 3703-3708
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Konferensbidrag (refereegranskat)abstract
- This study presented an experimental investigation on solidification behavior of fluid saturated in highly porous open-cell copper foams. Particular attention has been made on the effect of pore parameters (pore density and porosity) on the solidification behavior. A purposely-designed apparatus was built for experimental observations. Results showed that the copper foam had a great effect on solidification and the full solidification time can be saved up to 50%, especially preventing the decrease in solidification rate during the later stage of phase change. The smaller the porosity is, the faster the solidification rate will be. Pore density was found to have little influence upon the solidification rate. In addition, the local natural convection does exist but it has a slight effect on solidification, leading to the slant of the solid-liquid interface.
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| 10. |
- Belhomme, Regine, et al.
(författare)
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Bottom-Up Flexibility in Multi-Energy Systems : Real-World Experiences From Europe
- 2021
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Ingår i: IEEE Power and Energy Magazine. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1540-7977 .- 1558-4216. ; 19:4, s. 74-85
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Tidskriftsartikel (refereegranskat)abstract
- Electricity Systems in europe are experiencing major changes due to targets for renewable energy integration, reducing greenhouse gas emissions, and energy efficiency. Different studies show that there is a growing need for more flexibility and active stakeholder involvement at all levels (from small consumers to pan-European networks) to ensure the efficient and reliable operation of the electricity system, particularly to deal with growing volumes of renewable energy sources, from transmission-level wind and solar farms to household-level photovoltaic generation. Other key evolutions that aim to decarbonize the energy sector beyond electricity, such as those based on the electrification of energy end uses (e.g., the development of electric vehicles and the electrification of heating), are also expected to have a substantial impact.
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