低温装置用材料散水性能的研究

结合某低温装置的散水要求,运用自主研发的散水率测试仪对硬质泡沫材料、开孔泡沫材料、涂料等三种主要材料进行了散水率研究。结果表明,硬质泡沫材料通过包覆铝塑膜获得了低散水率,开孔泡沫材料散水率比硬质泡沫材料更低,环氧底漆与环氧清漆组成的涂料散水率可以满足技术要求。

Water Use of Leymus chinensis Community

Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspiration. It can be called interaction layer of precipitation and evapotranspiration. The layer (40-120 cm), where water-storage capacity exchange lagged exchange of the root-layer water-storage capacity and the community evapotranspiration, can be called major water-storage layer. The layer (under 120 cm) can be called water relatively stable/balanced layer. The year 1996 was a normal flow year, and soil water had a surplus of 18 mm at the end of the growing season. The year 1998 was a high flow year, because leakage took place under continuous heavy rainfall, soil water had a deficit of 15 mm at the end of the growing season. Transpiration to evapotranspiration ( T/ET) value reflected not only the luxuriance degree of the community, but also the water use regime of the environmental resources. T/ET value was low (0.5) in May 1998, reaching 0.7 in June, then decreasing to 0.6 in July, due to the impact of rainfall inclining, while August reached the maximum (0.9), and September decreased to 0.6. Water use efficiency (WUE) was mainly restricted by the growing rate of plants under sufficient water condition (1998). Its seasonal changes were coincident with the grand period of growth of the plants. When both meanings of WUE and T/ET were analyzed profoundly, the concept of evapotranspiration efficiency (ETE) which can all-side reflect utilization regime of the environmental water resources was advanced.

Controlling dispersion and morphology of MoS2 nanospheres by hydrothermal method using SiO2 as template

Monodispersed MoS_2 nanospheres were successfully synthesized by using SiO_2 as hard template. The size and morphology of the MoS_2 nanospheres could be finely controlled by the content of SiO_2 and sulfur precursors. Furthermore, higher surface area of monodispersed MoS_2 nanospheres exhibited high reaction rate for hydrodesulfurization(HDS) of dibenzenethiophene(DBT).

Numerical calculation of dispersion relation for linear internal waves

With the horizontal Coriolis terms included in motion equations and the influence of compressibility of seawater on Brunt-Vaeisiaelae frequency considered, a numerical method of calculating the dispersion relation for linear internal waves, which is an improvement of Cai and Gan （1995）, and hence Fliegel and Hunkins （1975）, had been set up. For different models （Pacific model, Atlantic model and Arctic model）, simulations using the three different methods were compared and the following conclusions were reached： （1） the influence of horizontal Coriolis terms on dispersion relation cannot be neglected and is connected with the direction of the wave celerity, the latitude, and the modes of the wave （2） the effect of compressibility of seawater in stratification is not an important factor for the dispersion relation of linear internal wave, at least for those three models, With the improved method, the wavefunction curves for the Pacific model had also been built.

Pilot Study on Adjustable Head Fall Mixer with Grids for Rapid Mixing

The performance of adjustable head fall mixer is studied in a pilot experiment. Experimental results indicate that the dispersal efficiency increases with the space between grids and mixing pipe, which could be up to 96%. When the flow rate increases more than 31%, the dispersal efficiency decreases a little but still above 96%. It is demonstrated that special coagulant injection head makes significant Contribution to improving the mixer efficiency. The almost same turbidity of sedimentation effluent could be achieved with less coagulant, thus 30% chemical can be saved. Dissolved oxygen increases 2.5 mg/L in the mixing unit, which will benefit the following processes.

Kinetics for Describing the Creaming of Protein-Stabilized O/W Emulsions by Multiple Light Scattering

In the present work, new kinetics to describe the creaming stability of oil-in-water emulsions determined by backscattering measurements （BS） is proposed. The emulsions assayed exhibited a different backscattering profiles regarding creaming destabilization hyperbolic and sigmoid one. Hyperbolic behavior can be described by a second order kinetics, where k_h could be equaled to a rate constant that describes the creaming process and its values would indicate the stability of emulsions. While for the sigmoid BS pattern, kinetics with two terms, is adequate to describe the creaming process in contrast to kinetics previously reported in the literature. The kh value has the same meaning as before, and ks indicates the delaying effect on the creaming rate.

Chemical Composition of Summertime PM_(2.5) and Its Relationship to Aerosol Optical Properties in Guangzhou,China

Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical properties of aerosols were conducted in July 2008 at an urban site in Guangzhou,Southern China.The mean PM 2.5 concentration for the entire period was 53.7±23.2 μg m 3.The mean PM 2.5 concentration (82.7±25.4 μg m 3) on hazy days was roughly two times higher than that on clear days (38.8±8.7 μg m 3).The total water-soluble ion species and the total average carbon accounted for 47.9%±4.3% and 35.2%±4.5%,respectively,of the major components of PM 2.5.The increase of secondary and carbonaceous aerosols,in particular ammonium sulfate,played an important role in the formation of haze pollution.The mean absorption and scattering coefficients and the single scattering albedo over the whole period were 53±20 M m 1,226±111 M m 1,and 0.80±0.04,respectively.PM 2.5 had a high linear correlation with the aerosol extinction coefficient,elemental carbon (EC) was correlated with aerosol absorption,and organic carbon (OC) and SO 4 2 were tightly linked to aerosol scattering.

Water Consumption of Seven Forage Cultivars under Different Climatic Conditions in the North China Plain

The objectives of this study were to determine the characteristics of water consumption of seven forage cultivars, ryegrass （Secale cereale L.）, triticale （×Triticosecale Wittmack）, sorghum hybrid sudangrass （Sorghum biolor× Sorghum Sudanense c.v.）, ensilage corn （Zea mays L.）, prince’s feather （Amaranthus paniculatus L.）, alfalfa （Medicago sativa L.）, and cup plant （Silphium perfoliatum L.）, in response to climate variability （especially precipitation）. Field experiments were conducted at Yucheng Integrated Experiment Station from 2005 to 2009. Fifteen irrigated lysimeters were used to measure evapotranspiration （ET） and crop coefficient （Kc） of these seven forage varieties under ample water supply. The mean Kc for alfalfa is 1.08, and the mean Kc for other forage varieties ranges from 0.79 to 0.94. Kc for hibernating forage is higher in wet years than that in dry years, followed by normal years, while for annual forage, Kc is higher in dry years than in normal years, and is the lowest in wet years. For perennial varieties the order is normal years, dry years, and wet years. Among the annual varieties, ensilage corn is the first choice due to its highest average forage N yield and water use efficiency （WUE）. Sorghum hybrid sudangrass is another forage cultivar that grows well under all climatic conditions. It can achieve 1.08-2.31 t ha-1 y-1 N yield under all circumstances. Prince’s feather is sensitive to climate change and its N yield dropped below half even when ample water was applied in dry and normal years. Ryegrass and triticale have the advantage of growing in the fallow phase after cotton is harvested in the North China Plain （NCP） and the latter performed better. For perennial varieties, alfalfa performed better than cup plant in dry years. With ample irrigation, alfalfa can achieve higher biomass and WUE under arid climate condition, but excessive rain caused reduction in production.

Distribution optimization of circulating water in air-cooled heat exchangers for a typical indirect dry cooling system on the basis of entransy dissipation

The flow and heat transfer of air-cooled heat exchangers play important roles in the performance of indirect dry cooling systems in power plants,so it is of benefit to the design and operation of a typical indirect dry cooling system to optimize the thermo-flow characteristics of air-cooled heat exchangers.The entransy dissipation method is applied to the performance optimization of air-cooled heat exchangers in this paper.Two irreversible heat transfer processes in air-cooled heat exchangers,the heat transfer between circulating water and cooling air and the mixing of circulating water,are taken into account and analyzed by means of the entransy dissipation method.The total entransy dissipation rate,which connects the geometrical parameters of air-cooled heat exchanger sectors and the heat capacity rates of the fluids to the heat flow rate in every sector,is obtained.Based on the mathematical relation and the conditional extremum method,an optimization equation group is derived,by which the air-cooled heat exchanger with known air-side parameters is optimized,showing that the entransy dissipation based optimization approach can contribute to the distribution optimization of circulating water in air-cooled heat exchangers of a typical indirect dry cooling system.

Experimental Study on Latent Heat Storage Characteristics of W/O Emulsion-Supercooling Rate of Dispersed Water Drops by Direct Contact Heat Exchange

Recently, much attention has been paid to investigate the latent heat storage system. Using of ice heat storage system brings an equalization of electric power demand, because it will solved the electric -power-demand-concentration on day-time of summer by the air conditioning. The flowable latent heat storage material, Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enable to transport the latent heat in a pipe. The flowable latent heat storage material can realize the pipe size reduction and system efficiency improvement. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase brings the obstruction of latent heat storage. The latent heat storage rates of dispersed water drops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The water drops in emulsion has the diameter within 3 ~ 25μm, the averaged water drop diameter is 7.3μm and the standard deviation is 2.9μm. The direct contact heat exchange method is chosen as the phase change rate evaluation of water drops in W/O emulsion. The supercooled temperature and the cooling rate are set as parameters of this study. The evaluation is performed by comparison between the results of this study and the past research. The obtained experimental result is shown that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It was clarified that the supercooling rate of dispersed water particles in emulsion shows the larger value than that of the bulk water.