Guodian Power Development Company Ltd

Beijing, China

Guodian Power Development Company Ltd

Beijing, China
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Zhao J.-J.,Tsinghua University | Zhao J.-J.,Guodian Power Development Company Ltd | Duan Y.-Y.,Tsinghua University | Wang X.-D.,North China Electrical Power University | Wang B.-X.,Tsinghua University
Journal of Heat Transfer | Year: 2013

A model based on the augmented Young-Laplace equation and kinetic theory was developed to describe the nanostructured roughness effects on an extended evaporating meniscus in a microchannel for Wenzel and Cassie-Baxter states. The roughness geometries were analytically related to the disjoining pressure, slip length and thermal resistance across the roughness layer. The results show that the equivalent Hamaker constant and adsorbed film thickness increase with nanopillar height for Wenzel state. Thus, the spreading and wetting properties of the evaporating thin film increase with roughness for Wenzel state, leading to an elongated thin film and enhanced heat transfer rate compared to a flat hydrophilic surface. The equivalent Hamaker constant and disjoining pressure effect decrease with increasing nanopillar height for Cassie-Baxter state. The system wettability, thin film length and heat transfer rate increase with increasing slip length and with decreasing roughness for Cassie-Baxter state. A smaller roughness coexisting with a larger slip length on rough surfaces for Cassie-Baxter state results in a much higher heat transfer rate relative to a flat surface. Copyright © 2013 by ASME.


Zhao J.-J.,Tsinghua University | Zhao J.-J.,Guodian Power Development Company Ltd | Duan Y.-Y.,Tsinghua University | Wang X.-D.,North China Electrical Power University | Wang B.-X.,Tsinghua University
Journal of Physics D: Applied Physics | Year: 2013

An analytical heat transfer model based on scanning electron microscopy, Brunauer-Emmett-Teller and pycnometry measurements and a 3D random diffusion-limited cluster-cluster aggregation structure is proposed to calculate the temperature-dependent microstructural parameters and thermal conductivities of silica aerogels. This model is a pure prediction model, which does not need experimentally fitted empirical parameters and only needs four measured structural parameters as input parameters. This model can provide high-temperature microstructural and thermophysical properties as well as theoretical guidelines for material designs with optimum parameters. The results show that three stages occur during the thermal evolution processes of the aerogel structure with increasing temperature from 300 to 1500 K. The current analytical model is fully validated by experimental data. The constant structure assumptions used in previous heat transfer models are found to cause significant errors at higher temperatures as the temperature-dependent structure deformation significantly increases the aerogel thermal conductivity. The conductive and total thermal conductivities of silica aerogels after high-temperature heat treatments are much larger than those with no heat treatment. © 2013 IOP Publishing Ltd.


Zhao J.-J.,Tsinghua University | Zhao J.-J.,Guodian Power Development Company Ltd | Duan Y.-Y.,Tsinghua University | Wang X.-D.,North China Electrical Power University | And 6 more authors.
International Journal of Thermal Sciences | Year: 2013

An inverse model based on the shooting method, Mie theory and the improved Kramers-Kronig (KK) relation was combined with FTIR and Abbe refractometer measurements to calculate the complex refractive indices of various infrared opacifiers. The effects of opacifier sizes, types and shapes were then analyzed based on the Rosseland mean extinction coefficient using Mie theory and anomalous diffraction theory (ADT). This model provides theoretical guidelines for designing materials with optimized parameters, such as size, type and shape of opacifiers, to improve the aerogel thermal insulation at high temperatures. The results show that the optimum diameter of SiC particles to minimize the radiation is 4 μm for T < 400 K and 3 μm for T > 400 K. Carbon black is the optimum opacifier for T < 600 K while SiC is the optimum opacifier to minimize the radiative heat transfer for T > 600 K among the investigated opacifiers of SiC, TiO2, ZrO2, amorphous SiO2 and carbon black. The infrared extinction ability for various shapes is largest for oblate spheroids and decreases for spheres, cubes, cylinders with small length-to-diameter ratios, and then long, thin cylinders. © 2013 Elsevier Masson SAS. All rights reserved.


Mi J.F.,Guodian Energy Research Institute | Sun J.,Guodian Power Development Co. | Luo W.,China Electric Power Research Institute
Frontiers of Energy and Environmental Engineering - Proceedings of the 2012 International Conference on Frontiers of Energy and Environmental Engineering, ICFEEE 2012 | Year: 2013

The wind power in China has been going through a period of rapid development in recent years. In this paper, the main data of wind power installed capacity, grid-connected capacity, and the generation during 2008 to 2011 has been collected and researched to analyze the proportion of wind power grid integration in top 10 provinces in China and the situation of wind power curtailment in 2011. Furthermore, difficulties in wind power grid integration have been concluded based on perspectives of technical, political and economical factors. In the end, some recommendations have been proposed in the issue of future wind power grid integration. © 2013 Taylor & Francis Group.


Zhao J.-J.,CAS Institute of Process Engineering | Zhao J.-J.,Guodian Power Development Company Ltd | Yu H.-T.,CAS Institute of Process Engineering | Duan Y.-Y.,CAS Institute of Process Engineering | And 2 more authors.
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2013

The parallel proportion factor of solid-gas thermal conductions was presented based on the very realistic aerogel structure. An analytical heat transfer model was then developed with full considerations of the aerogel microstructure and the nanoscale thermal conduction effects. The results show that this model can well predict the total thermal conductivity of aerogels for various pressures, temperatures, densities and microstructures. This model can be used to quickly predict and optimize the relationship between the thermal conductivity and the microstructure. The total thermal conductivity of silica aerogels reaches its minimum at a density of 130 kg·m-3 at ambient conditions. The total thermal conductivity of aerogels decreases with increasing the number of secondary nanoparticles at high temperatures. Thus, the thermal insulating performance of aerogels is mainly affected by the number of secondary nanoparticles at high temperatures.

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