Ti(OC4H9)4 was used as the Ti precursor and titanium dioxide (TiO2 ) was prepared by sol-gel method. During the preparation process, Fe3+ was doped and different surfactants, such as SDS, PEG, CTAB, were added to impr...
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ISBN:
(纸本)9783037856062
Ti(OC4H9)4 was used as the Ti precursor and titanium dioxide (TiO2 ) was prepared by sol-gel method. During the preparation process, Fe3+ was doped and different surfactants, such as SDS, PEG, CTAB, were added to improve the photocatalytic activity of TiO2 . The effect of the different type of surfactants on the structure of Fe-doped TiO2 was discussed. The photocatalysts were characterized by thermogravimetric thermal analysis, X-ray diffraction, scanning electron microscopy and UV-Vis spectrophotometer. The red shift of the absorption edge of the Fe-doped TiO2 prepared by using different surfactants was observed. Methyl orange (MO) solution was degraded under sunlight irradiation to evaluate the photocatalytic performance. The results indicated that the photocatalyst prepared with PEG addition had the highest activity and MO degradation ratio could reach 90% after 4 hours irradiation with the best photocatalyst.
Solar collector is one of the most important parts of solar chimney power plant. It plays an important role in improving the efficiency and saving the cost of the whole system. In this paper, several transparent mater...
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ISBN:
(纸本)9781622765447
Solar collector is one of the most important parts of solar chimney power plant. It plays an important role in improving the efficiency and saving the cost of the whole system. In this paper, several transparent materials which could be used as the collector were chosen to study the optical properties. The materials include polymethyl methacrylate (PMMA), polycarbonate (PC), perspex (PS) and ordinary glass. Firstly, an experiment device was designed with the collector angles varying from 15° to 60°. Secondly, different thickness of glass and different slope angles of the collector of these materials mentioned above on transmittance was compared. The effect of pollutions caused by the natural environment such as dust, rain and aging on these materials was considered in the experiment. Based on the experimental results, a conclusion was made that PMMA has the highest transmittance among the four materials without considering other factors.
Experiments were carried out to investigate condensation of ethanol-water vapor mixtures on a vertical mini-tube with outer diameter of 1.032 *** length,inter diameter of the tube was 110 mm,0.727 mm,*** tests were pe...
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Experiments were carried out to investigate condensation of ethanol-water vapor mixtures on a vertical mini-tube with outer diameter of 1.032 *** length,inter diameter of the tube was 110 mm,0.727 mm,*** tests were performed at a wide range of ethanol concentrations(Cv=0%,1%,2%,5%) and varied velocity of vapor(Uv=2m/s,4m/s,6m/s) and pressure(Pv=31.2kPa,47.4kPa,84.5kPa).With the change of the vapor-to-surface temperature difference,the heat transfer coefficients revealed nonlinear characteristics with the peak values under all ethanol mass fractions of *** heat transfer coefficients decreased with increasing ethanol mass fraction of vapor.
One set of one-dimensional unsteady homogenous mathematic models for flow and heat process of natural circulation precooling loop of cryogenic liquid rocket engine was established, whilst both inverted annular model a...
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One set of one-dimensional unsteady homogenous mathematic models for flow and heat process of natural circulation precooling loop of cryogenic liquid rocket engine was established, whilst both inverted annular model and dispersed model were introduced for the prediction of filming boiling region. The results indicate the unstable characteristics of circulation flow rate in precooling process is caused by the unstable characteristics of natural circulation driving force, that is, the heat flux transferred to the cryogenic liquid from the natural circulation precooling loop. Moreover, about 80% of wall temperature drop takes place in filming boiling region, and the inverted temperature distribution law of the return pipe is well interpreted by introducing the two filming boiling models mentioned above.
Heat transfer performance of working medium is important for supercritical units. In this work, heat transfer experiments and simulations were carried out at 25 to 29.8 MPa. The impacts and influence mechanisms of ope...
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Exergy analysis of solar dynamic closed Brayton cycle (SDCBC) for space applications was presented in this paper. An integrated model for the system and specific models for its components were proposed. Influence of m...
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Exergy analysis of solar dynamic closed Brayton cycle (SDCBC) for space applications was presented in this paper. An integrated model for the system and specific models for its components were proposed. Influence of main parameters on system exergy efficiency was discussed. The results shown the efficiencies of expander, compressor, and regenerating temperature of the regenerator have significant influence on the exergy efficiency of SDCBC system. Therefore, besides the enhancement of component efficiencies, the matching among components of SDCBC system should be also taken into account. Moreover, it would be always desirable to enhance the effectiveness of recuperator within the requirements of flow resistance and system weight.
Objective Photoacoustic tweezers (PATs) are a promising noninvasive technology for precise microparticle manipulation that leverage the photoacoustic effect to exert controlled forces on particles within a liquid medi...
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Objective Photoacoustic tweezers (PATs) are a promising noninvasive technology for precise microparticle manipulation that leverage the photoacoustic effect to exert controlled forces on particles within a liquid medium. Conventional methods, such as optical and acoustic tweezers, present limitations such as potential damage to particles, inadequate spatial control, and restricted manipulation in three-dimensional (3D) environments. Hence, this study focuses on the theoretical development of a PAT model that integrates photo-thermo-acoustic-mechanical coupling effects. Using a ring-shaped laser beam, this study aims to investigate particle motion and force characteristics under various laser conditions. Additionally, this study seeks to establish a robust theoretical framework for PATs, thus filling the gaps in 3D particle manipulation and providing guidance for the optimization of experimental parameters. Methods A multiphysics coupling model for PATs was constructed to describe the interactions among photo-thermal, acoustic, and mechanical effects in a liquid medium. The model accounts for the transformation of laser energy density into heat and the subsequent thermal expansion, and the generation of acoustic waves that induces acoustic radiation forces and acoustic streaming. A ring-shaped laser beam was employed to create spatially confined acoustic fields that can trap and manipulate particles. Using the finite-element method (FEM) in Comsol software, the model was used to simulate high-frequency pulsed laser effects, including energy transfer, thermal expansion, acoustic wave propagation, and the resultant particle dynamics. The governing equations for the coupled fields were derived by incorporating the spatial and temporal distributions of the laser, the thermal and acoustic properties of the medium, and force interactions on the particles. The acoustic radiation forces were modeled based on Gor’kov potential theory, whereas the acoustic streaming fields wer
The Pb spectral concentration of atmospheric aerosol samples observed over Mount Qomolangma site （28° 11＇33＂N, 86°49＇S9＂E, 4950m ASL） in 2002 was 13.3 ng/m^3, about 4.5 times higher than that in 2000. ...
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The Pb spectral concentration of atmospheric aerosol samples observed over Mount Qomolangma site （28° 11＇33＂N, 86°49＇S9＂E, 4950m ASL） in 2002 was 13.3 ng/m^3, about 4.5 times higher than that in 2000. The Pb spectral distribution showed three peaks, located at 〈0.25 μm, 0.5-1 μm, and 4-8 μm in diameters. The peaks for 〈0.25 μm and 0.25-0.5 μm may be due to long-distant transport, while that for 4-8 μm probably results from local floating dust. The atmospheric Pb concentration over Mount Momolangma was lower than that of South Pole, most of the urban areas, and desert areas in the northern hemisphere. The enrichment factors for fine and coarse particles of atmospheric Pb in 2002 over Mount Qomolangma were 413.2 and 62,6, respectively, in support of the slight atmospheric pollution with Pb over the Qinghai- Tibetan Plateau.
Experiments on the condensation of steam jet submerged in the subcooled water were carried out. The water temperature and the inlet steam pressure were in the range of 293 K–343 K and 0.2–0.6 MPa, respectively. Four...
Experiments on the condensation of steam jet submerged in the subcooled water were carried out. The water temperature and the inlet steam pressure were in the range of 293 K–343 K and 0.2–0.6 MPa, respectively. Four essential shapes of steam plume were enumerated. According to the comparisons of the pictures of steam plume with the graphs in the same size, the pressure came to maximum value in the contraction spots, except for the double expansion‐emanative shape. Moreover, pressure distributions of the flow field were characterized by means of drawing isobar. Comparison and discussions on the relationship between steam plume and pressure distributions were given. With the increase of temperature, pressure distributions within steam plume became more complex. Radial pressure distributions were classified according to different regions. Comparisons of the pressure distributions at different water temperature and inlet steam pressure were obtained.
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