| 1. |
- Huang, C., et al.
(författare)
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Understanding the water-energy nexus in urban water supply systems with city features
- 2018
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Ingår i: CLEANER ENERGY FOR CLEANER CITIES. - : Elsevier. ; , s. 265-270
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Konferensbidrag (refereegranskat)abstract
- The water-energy nexus has been introduced into urban water supply systems (WSSs) to improve the current plight of scarce resources and greenhouse effect in recent years. Urban water-energy integrated management is limited by the characteristics and reality of each city. In this paper, we characterize the comprehensive influence factors of energy use in China urban WSSs including geographic differences and city forms. The results indicate that the pressure of pipeline network and plain area ratio restricted by geomorphology would significantly impact the energy consumption during conveyance and distribution stage. For the city form aspect, the total volume of urban water supply and the leakage rate of pipeline networks play important roles in energy consumption of urban WSSs in China. In this study, the specific electricity consumption in WSSs was quantified, and several factors affected by city features which show strong correlation with energy use were determined. The results are of great significance to the energy saving in water supply systems in urban areas.
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| 2. |
- Andersson, Per A., et al.
(författare)
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Anger and disgust shape judgments of social sanctions across cultures, especially in high individual autonomy societies
- 2024
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- When someone violates a social norm, others may think that some sanction would be appropriate. We examine how the experience of emotions like anger and disgust relate to the judged appropriateness of sanctions, in a pre-registered analysis of data from a large-scale study in 56 societies. Across the world, we find that individuals who experience anger and disgust over a norm violation are more likely to endorse confrontation, ostracism and, to a smaller extent, gossip. Moreover, we find that the experience of anger is consistently the strongest predictor of judgments of confrontation, compared to other emotions. Although the link between state-based emotions and judgments may seem universal, its strength varies across countries. Aligned with theoretical predictions, this link is stronger in societies, and among individuals, that place higher value on individual autonomy. Thus, autonomy values may increase the role that emotions play in guiding judgments of social sanctions.
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| 3. |
- Du, Z., et al.
(författare)
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Melting-solidification cycle of finned heat storage tank : Optimization of fin structure by response surface method
- 2023
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Ingår i: Case Studies in Thermal Engineering. - : Elsevier Ltd. - 2214-157X. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the enhanced heat transfer performance of longitudinal fins on the entire process of melting and solidification in a phase change heat storage unit is investigated through experiments and numerical simulations in this paper. The position and structure of the longitudinal fins are optimized by using the response surface method while ensuring that the total volume of the heat storage medium remains unchanged. Studies have identified that some challenging zones in melting and solidification significantly impact the heat transfer of the entire heat storage cycle. Specifically, the challenging zone in melting primarily exists in the lower part of the unit during the charing process, while the challenging zone in solidification is mainly distributed around the unit during the discharging process. Through optimization, the optimized structure (fin spacing is 22.5 mm, fin width is 6.05 mm) can reduce the charging and discharging time by 16.94 % and 45.90 %, respectively. Additionally, the round trip time is significantly reduced by 39.19 %, and the mean heat absorption rate during the melting process is enhanced by 20.28 %. Moreover, the mean heat release rate during solidification is enhanced by 80.23 %.
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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. |
- Huang, X., et al.
(författare)
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Design and optimization of a novel phase change photovoltaic thermal utilization structure for building envelope
- 2023
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Ingår i: Renewable energy. - : Elsevier Ltd. - 0960-1481 .- 1879-0682. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- The building envelope is of great significance for building thermal comfort, and photovoltaic heat (PV/T) can be effectively utilized through phase change heat storage technology to reduce heating energy consumption. In this paper, a phase change heat storage structure with subzone rotation is proposed for the building envelope. A numerical model of a triplex-tube LHTES unit is established by using the enthalpy-porosity method and verified by experimental data. The study employs the Taguchi method to select rotation speed in different regions and fin/tube wall material as variables. The effects of different variables on heat release rate and solidification time are investigated, and the interaction of each parameter on solidification performance is analyzed through signal-to-noise ratio. The findings indicate that when the inner and outer tube speeds are 0.3 rpm and 0.5 rpm, respectively, compared to the initial model where both inner and outer tube speeds are 0.1 rpm, the average temperature response rate and the average heat release rate are increased by 51.47% and 61.04%, respectively. Meanwhile, the solidification time is shortened by 40.49%. However, the release of the total heat is reduced by 0.66%. The study concludes that increasing rotation speed or solidification consistency of PCM in different areas is of great value in enhancing overall solidification performance. Finally, the specific effect of increasing regional rotation speed on the solidification process is studied through temperature/flow rate monitoring in the unit.
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| 6. |
- Li, X., et al.
(författare)
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Performance comparison regarding loop heat pipes with different evaporator structures
- 2019
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Ingår i: International journal of thermal sciences. - : Elsevier Masson SAS. - 1290-0729 .- 1778-4166. ; 136, s. 86-95
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Tidskriftsartikel (refereegranskat)abstract
- The design of evaporator can clearly affect the performance of loop heat pipes (LHPs). In order to understand the influence, three different designs of evaporators were compared, including embedding vapor channels on the heating surface (Config_1), embedding vapor channels in the wick (Config_2), and separating the wick from the heating surface (Config_3). Based on the validated model, the operating temperature, the start-up time, and the transport distance, as key performance indicators, were studied. Results show that, to improve the performance of LHP, it is of importance to reduce the contacting area between the wick and the heating surface. Due to the existence of the steam chamber, the wick was separated from the heating surface in Config_3, resulting in the lowest operating temperature and the shortest start-up time. The pressure head of evaporation is also an important component of the driving force. For Config_3, since the evaporation happened in the steam chamber rather than in the wick, it had a longer transport distance than Config_1 and Config_2 at the same heat load.
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| 7. |
- Liang, X., et al.
(författare)
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Numerical investigations on outdoor thermal comfort for built environment : Case study of a Northwest campus in China
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 6557-6563, s. 6557-6563
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Konferensbidrag (refereegranskat)abstract
- Outdoor thermal comfort has been receiving more and more attentions due to the increased demand of outdoor activities during last decades. People require good thermal comfort when they are exposed to the outdoor thermal environment. However, the natural environment is severely suffering from the pollution of air, water as well as the extremely hot weather. Therefore, construction of ecological living environment is of great importance. To evaluate and improve the built environment, a campus area located in Northwest China was selected. Numerical simulations based on the software ENVI-met V4.0 were conducted and the effect of growing plants upon the outdoor thermal comfort was analyzed. Numerical results were compared using different thermal Indexes: Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI). Results demonstrated that UTCI gave a lower prediction than that of PET and was more suitable for evaluating the outdoor thermal comfort. Growing trees can significantly reduce the uncomfortable hours during hot summer but the improvement will reach the limitation after growing amount of trees.
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| 8. |
- Luo, H., et al.
(författare)
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Carbon emission prediction model of prefecture-level administrative region : A land-use-based case study of Xi'an city, China
- 2023
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 348
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Tidskriftsartikel (refereegranskat)abstract
- Climate change has become a global concern, and the prediction of carbon emissions is key to achieving carbon-reduction goals. The existing framework cannot accurately reflect the spatial distribution of carbon emissions, making it difficult to guide urban planning and management. Therefore, in this study, a carbon emission spatial simulation and prediction model was established. The model includes the GIS-Kernel Density sub-model for subdividing built-up area, the Land Use-Carbon Emission sub-model for establishing the correlation between land use and carbon emissions, the Multi Objective Programming-Principal Component Analysis-BP neural network sub-model for presetting development scenarios, and the Patch-generating Land-use Simulation sub-model for predicting. Xi'an was chosen as the study site, and two extreme scenarios were determined. A total of 373,318 development paths were segmented from the interval, and the optimal path was selected. All scenarios were simulated, and the carbon emissions and their spatial distribution were calculated. The results showed that the overall accuracy of the simulation exceeded 90%. Under the optimal path, Xi'an's carbon emissions reach 60.6 million tons at peak time, which will be reduced to 47.38 million tons by 2060. In addition, the model analyzed the temporal and spatial changes of carbon sources and sinks and drew up the path of carbon reduction by technology and urban planning. This model can provide a reference for regional carbon-reduction planning and carbon reduction technology implantation. It can propose strategies from the perspective of planning and management.
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| 9. |
- Luo, H., et al.
(författare)
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Real-time Characterization Model of Carbon Emissions Based on Land-use Status : A Case Study of Xi'an City, China
- 2024
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 434
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Tidskriftsartikel (refereegranskat)abstract
- The traditional carbon accounting method, with a lag of over 2 years due to the release time of statistical yearbooks, impedes timely policy adjustments in urban planning and management. Hence, there is an urgent need to establish a real-time carbon emissions characterization model. Xi'an which has a complex land-use structure was chosen as the study site and its carbon emissions were calculated using the Emission Factor Method. The GIS-Kernel Density (KD) model was constructed, and land use was subdivided based on Point of Interest (POI) and road network data. Based on the results of carbon emissions accounting and land-use subdivision, a Multilayer perceptron (MLP) model was established. The remote sensing (RS) images of Xi'an underwent supervised classification, and the carbon emissions of Xi'an were characterized based on the subdivision results and MLP model. The results show that: (1) The accuracy of the characterization model is more than 90%, and with the improvement of RS technology, the accuracy will be further improved; (2) Compared with the existing model, this model can real time reflect the spatial distribution of carbon emissions; (3) Atmospheric emission of Xi'an will be 41.92 million tons at the end of 2022, a decrease of 2.80 million tons compared with that of 2020, but an increase of 0.33 million tons from 2021. The north of Xi'an and periphery of the central urban area are the main carbon sink loss areas, while the east of Xi'an and north foot of the Qinling Mountains are carbon sink growth areas.
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| 10. |
- Zhu, K., et al.
(författare)
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Dynamic performance of loop heat pipes for cooling of electronics
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; 142, s. 4163-4168
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Tidskriftsartikel (refereegranskat)abstract
- With the performance improvement of electronics, the recent trends in electronic industry pose a big challenge on heat dissipation. Conventional methods, i.e. air cooling, may not be able to handle the fast increasing heat flux. Using heat pipes, which have numerous advantages such as high heat transfer coefficient, non-movable components, longer transport distance, and compact structures, emerges to be one competitive option for electronics cooling. Based on the node analysis method and the conservation of energy and mass, this work develops a mathematic model to simulate the operation of heat pipes. After it is validated against experimental data, it is further applied to evaluate the dynamic performance of using a heat pipe for electronics cooling. Results show that the operation temperature of evaporator ranges from 47.5°C to73.1°C, which implies that the heat pipe can effectively cool down the CPU at different running status. The charging ratio of working fluid is identified as a key parameter and exists an optimal value. When keeping the charging ratio constant, a larger evaporator area can achieve a lower operating temperature.
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