Search

Your search keyword '"Wu, Dongxu"' showing total 238 results
Start Over Author "Wu, Dongxu"
238 results on '"Wu, Dongxu"'

20. Influence Factors of the Evaporation Rate of a Solar Steam Generation System: a Numerical Study

Author

Zhong, Jinxin, Huang, Congliang, Wu, Dongxu, and Lin, Zizhen

Subjects
Physics - Applied Physics
Abstract

Many efforts have been dedicated to improve the solar steam generation by using a bi-layer structure. In this paper, a two-dimensional mathematical model describing the water evaporation in a bi-layer structure is firstly established and then the finite element method is used to simulate the effects of different influence factors on the evaporation rate. Results turn out that: besides the high solar energy absorptivity of the first-layer, an optimum porosity of the second-layer porous material should be applied and the optimum porosity is about 0.45 in this work. This optimum porosity is determined by the balance between the positive effect of the lowering effective thermal conductivity of the second layer and the negative effect of the reduced vapor diffusivity in the second layer when the porosity is decreased. The influence of the thermal conductivity of the second-layer porous material is negligible because the effective thermal conductivity of the second layer is determined by the porosity while a larger porosity means more water in the second layer. The ambient air velocity could greatly enhance the evaporation rate, and the evaporation rate will decrease linearly with the increase of the air relative humidity. This study is expected to supply some information for developing a more effective bi-layer solar steam generation system., Comment: arXiv admin note: substantial text overlap with arXiv:1806.06485

Published
2018

21. Surrounding Effects on the Evaporation Efficiency of a Bi-layered Structure in Solar Steam Generation: a Numerical Study

Author

Zhong, Jinxin, Huang, Congliang, and Wu, Dongxu

Subjects
Physics - Applied Physics
Abstract

The bi-layered structure has drawn a wide interest due to its good performance in solar steam generation. In this work, we firstly develop a calculation model which could give a good prediction of experimental results. Then, this model is applied to numerically study the effects of the depth of the liquid water, the temperature of the ambient air, the temperature of the liquid water, the porosity and the thermal conductivity of the second-layer porous material on the evaporation efficiency. Results show that when the depth of the liquid water is large enough, the thermal insulation at the bottom of the liquid water is not needed. There is a linear dependence of the evaporation efficiency on the temperature of the ambient air or/and the temperature of the liquid water, and an equation has been given to describe this phenomenon in the text. Compared to the temperature of the ambient air, the temperature of the liquid water could have a much larger effect on the evaporation efficiency. The effective thermal conductivity of the second layer, which could impose important effect on the evaporation efficiency, mainly depends on the porosity rather than the thermal conductivity of the second-layer porous material. Thus, we do not need to take into consideration of the thermal conductivity when selecting second-layer materials. This study is expected to provide some information for designing a high-evaporation-performance bi-layered system.

Published
2018

34. Performance analysis of solar thermal storage systems with packed bed utilizing form-stable phase change materials and heat pump integration.

Author

Wang, Changling, Gao, Yuanzhi, Yang, Juan, Liu, Baobin, Dai, Zhaofeng, Wu, DongXu, Xia, Yujiang, Yu, Jing, Yan, Weidong, and Zhang, Xiaosong

Subjects
HEAT storage, HEAT pumps, PHASE change materials, SOLAR thermal energy, ENERGY storage, TEMPERATURE distribution, THERMAL analysis
Abstract

Solar energy, a pivotal renewable resource, faces operational challenges due to its intermittent and unstable power output. Thermal energy storage systems emerge as a promising solution, with phase change materials (PCMs) packed beds attracting attention for their compactness and stable temperature transitions. This paper details a laboratory-scale solar thermal storage PCM packed bed integrated with a heat pump, utilizing a novel form-stable PCM. A numerical model was established to assess the thermal storage characteristics and heat extraction performance of the solar PCM packed bed coupled with a heat pump. Simulation results show that increasing solar irradiance significantly reduces storage duration, achieving full thermal storage in 3.4 h at 900 W/m2 irradiance. Optimal starting times were identified as 9:00 a.m. or 11:00 a.m., with later starts resulting in incomplete storage due to the PCM not reaching its phase change temperature. Additionally, packed bed parameters influenced storage conditions; increasing the paraffin content in the PCM extended the phase change duration, while graphene nanoparticles slightly reduced it. Lower porosity (0.49) beds, with higher PCM content, reached 70 °C quicker than higher porosity (0.61) beds due to higher pressure drops promoting more uniform flow and temperature distribution. During heat extraction, coupling the heat pump at 2 liters/min achieved temperatures below 45 °C in 4.1 h, while at 6 liters/min, the time reduced to 1.6 h, demonstrating adaptability to different extraction rates. These findings provide insight into the thermal performance of solar PCM packed beds coupled with heat pumps, contributing to efficient and stable thermal utilization of solar energy. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

49. Internal and External Cultivation Design of Zero‐Strain Columbite‐Structured MNb2O6 toward Lithium‐Ion Capacitors as Competitive Anodes.

Author

Cheng, Chao, Wu, Dongxu, Gong, Tianyu, Yan, Yunshen, Liu, Yang, Ji, Weixiao, Hou, Linrui, and Yuan, Changzhou

Subjects
*IONIC conductivity, *ANODES, *CAPACITORS, *ENERGY density, *STRUCTURAL stability, *LITHIUM ions, *ELECTRIC batteries
Abstract

Modest rate behaviors and structural collapse of battery‐type anodes limit the commercial application of lithium‐ion capacitors (LICs). For this, rational design of advanced anodes with both structural stability and high ionic/electronic conductivities becomes essential to advanced LICs. Herein, a general avenue is developed to construct a series of single‐crystal nano‐blocks assembled as "zero‐strain" columbite‐structured MNb2O6 (M = Cd, Co, Zn, Mn, Mg, Ca) accordion frameworks toward LICs. The intrinsic Li+ (de)insertion involves a solid‐solution charge storage mechanism with a volumetric change of <0.59% over (de)lithiation as established with systematical in(ex) situ analysis. The MNb2O6 exhibits M‐dependent electron/ion transport capabilities, along with the highest electronic and Li+ diffusion rates and the smallest volume change (0.32%) for CdNb2O6. Thanks to its robust structure and superb electron/ion conductivities originating from the "internal (i.e., ionic/electronic transport optimization) and external (i.e., structural design) cultivation" design, the CdNb2O6 shows the optimum electrochemical behaviors with a capacity of 102.8 mAh g−1 at 10 A g−1 and capacity retention of 80.3% after 20 000 cycles at 5 A g−1. The assembled CdNb2O6‐based LICs display high‐rate energy density and long‐duration stability. More importantly, the devised strategy provides meaningful guidance for optimum design of next‐generation LICs. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results