基于相变材料的太阳能PV/T系统性能

利用相变材料（phase change material, PCM）的定温储放热特性,将脂肪酸类PCM填充在装有金属肋片的集热器中,对太阳能光伏（photovoltaic, PV）板进行温度调控,实验分析了不同间歇性热量调控策略下PV/T（photovoltaic/thermal）-PCM系统宏观性能。结果表明：PCM能有效缓解光伏电池的温度波动,但系统运行中PCM的温度分层现象较为严重,制约了其实际利用率;合理的热量调控策略对防止PV/T-PCM系统中光伏电池过热及提升系统性能至关重要,数据显示工况二（调控温度设为45℃,调控时长30 min）和工况三（调控温度设为50℃,调控时长30 min）在调控前后,其光电转换效率分别提升3.4%和2.6%;工况二对应的系统总效率为90.8%,工况三为84.45%,均在工况一（无调控）的基础上有显著提升。     

Evolution of bubble size distribution,number density,and shape in semi-batch vertical gas–liquid Taylor vortex flow

Bubble size distribution and bubble ellipticity were measured as a function of axial position in a vertically oriented semi-batch gas–liquid Taylor vortex reactor with varying gas flow rate and inner cylinder rotation speed producing axial Reynolds numbers in the range 23.8–119 and azimuthal Reynolds numbers up to 4.2 × 10⁴. The mean bubble size increases monotonically with axial distance from the bottom of the reactor at the location of gas injection. The functional form of the growth of the mean bubble size with axial position depends upon the azimuthal Reynolds number. Specifically, when the azimuthal Reynolds number is less than 1.3 × 10⁴, the mean bubble size increases linearly with axial distance from the bubble injection point. In contrast, for azimuthal Reynolds numbers greater than this critical value, the mean bubble size increases with axial distance in a sigmoidal manner.     

Effect of zirconia on ablation mechanism of asbestos fiber/phenolic composites in oxyacetylene torch environment

Micron-size zirconium oxide (ZrO₂) was used to improve the thermal stability and ablation properties of asbestos fiber/phenolic composites and to reduce their final cost. ZrO₂/asbestos/phenolic composites were prepared in an autoclave by the curing cycle process. The densities of the composites were in the range of 1.64–1.82 g/cm³. The ablation properties of composites were determined by oxyacetylene torch environment and burn-through time, erosion rates and back surface temperature in the first required 20 s. To understand the ablation mechanism, the morphology and phase composition of the composites were studied by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Thermal stability of the produced materials was estimated by means of thermal gravimetric analysis, in air which consisted of dynamic scans at a heating rate of 10 °C/min from 30 to 1000 °C with bulk samples of about 23±2 mg. The thermal stability of the composites was enhanced by adding ZrO₂. The results showed that the linear and mass ablation rates of the composites after adding 14 wt% ZrO₂ decreased by 58% and 92%, respectively. The back surface temperature of a sample with 14% zirconia was 49% lower than that of pure composite. The SEM studies showed that, modified composites displayed much lower porosity than that of non-modified composite and the destruction of asbestos fibers was very low. On the other hand, it appeared that a thin melted layer of ZrO₂ covered the surfaces of zirconia-containing composites.     

Microstructure and mechanical properties of friction stir weld of dissimilar AZ31-O magnesium alloy to 6061-T6 aluminum alloy

Dissimilar friction stir welding between AZ31-O Mg and 6061-T6 Al alloys was investigated. 3 mm thick plates of aluminum and magnesium were used. Friction stir welding operations were performed at different rotation and travel speeds. The rotation speeds varied from 600 to 1400 r/min, and the travel speed varied from 20 to 60 mm/min. Defect-free weld was obtained with a rotation speed of 1000 r/min and travel speed of 40 mm/min. Metallographic studies showed that the grain size in the stir zone is much finer than that in the base metals. Complex flow pattern was formed in the stir zone. Microhardness measurement revealed an uneven distribution in the stir zone. Tensile test results indicated that the tensile strength of the welded specimen is about 76% of AZ31 Mg alloy and 60% of the 6061 Al alloy in tensile strength. SEM fracture surface image of the welded specimen indicated that the welded specimen failed through brittle-mode fracture.     

Modeling of annular reactors with surface reaction using computational fluid dynamics (CFD)

A CFD-based model for predicting the performance of annular reactors with surface reaction was developed. The capability of several hydrodynamic models to predict successfully the kinetic behavior of the reactor under diffusion limiting conditions was assessed against experimental data. The evaluation included five models: laminar, standard k–ε, realizable k–ε, Reynolds stress (RSM), and Abe–Kondoh–Nagano (AKN). The catalytic decomposition of hydrogen peroxide over a Mn/Al oxide catalyst coated on the reactor surface was used as a model reaction. The reactor was tested within a range of flow rates corresponding to 530<Re<11,000 and intrinsic reaction rate constants of 5×10^?5 to 1 m/s. The results demonstrated that the performance of the hydrodynamic models is associated with their capability to predict external mass transfer and ultimately, the level of mass transfer limitation present in the reacting system. For laminar flow conditions, the laminar model is capable of predicting the experimental behavior of the system. For transient and turbulent flow regimes, all the analyzed turbulence models provided good predictions of the system when the process was controlled by surface reaction. When the system presented some degree of mass transfer limitation, AKN and RSM exhibited better performance.     

Thermodynamic and Electrochemical Studies of Aniline and Phenylhydrazine and Their Derivatives Substituted POCl3-Based Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Protection of Metals and Physical Chemistry of Surfaces - The achievement of high corrosion inhibition performances by manipulating the molecular structure of organic substances has gained much...     

Effects of sodium hydroxide and calcium hydroxide on polyester fabrics

The results of a comparison between the effects of sodium hydroxide and calcium hydroxide on poly(ethylene terephthalate) fabrics are presented. Calcium hydroxide can produce weight‐loss effects similar to an aqueous solution of sodium hydroxide. The effects of some treatment variables on weight loss, fiber diameter, bending rigidity, and strength of yarns taken from fabrics are examined. The results are explained in terms of current views of polyester alkaline hydrolysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 631–637, 1999     

能源、环境与空调制冷

１９９７年,世界上１６０多个国家在日本京都签订了有关减少温室气体排放的协议（京都协议）。该协议对缔约国的能源政策甚至经济的发展都有巨大的影响。作为能源消耗量很大的空调制冷行业,有必要对此予以充分的关注和深入研究。本研究了国内外能源环境现状和空调制冷系统与能源环境的关系,给出了对空调制系统适应新的能源结构和环境政策进行适当调整的建议。     

Water—ethanol—gasoline blends as spark ignition engine fuels

The miscibility characteristics of hydrated ethanol with gasoline is investigated as a means of reducing the cost of ethanol/gasoline blends for use as a spark ignition engine fuel. For a given percentage of water in the ethanol, the experimental data shows that a limited volume of gasoline can be added to form a stable mixture. Engine experiments indicate that, at normal ambient temperatures, a water/ethanol/gasoline mixture containing up to 6 vol% of water in the ethanol constitutes a desirable motor fuel with power characteristics similar to those of the base gasoline. As a means of reducing the smog causing components of the exhaust gases, such as the oxides of nitrogen and the unburnt hydrocarbons, the water/ethanol/gasoline mixture is superior to the base gasoline.     

Airflow and heat transfer in double skin facades

Airflow and heat transfer simulation was conducted for a DSF system equipped with a venetian blind, using computational fluid dynamics (CFD) with RNG turbulence model, for a three-level combination of slat tilt angle and blind position. The CFD prediction was validated using experimental data collected for a mechanically ventilated DSF equipped with venetian blinds. The predicted trends in glass and blind surface temperatures of the CFD model are compared well with the experimental measurements. The present study indicates that the presence of venetian blinds influences the surface heat transfer coefficients (SHTCs), the temperature and the air distribution in the DSF system. For the cases considered, the changes in the position of the blinds (outer, middle, and inner) have more effect on the distribution of temperature, velocity, and SHTCs compared to the changes in the slat angles (θ = 0°, 45°, 90°).