反应堆压力容器下降段水-蒸汽CCFL实验与模型研究

为探究反应堆压力容器下降段在喷放末期冷段安注过程中的水-蒸汽逆流特性,建立下降段逆向流动限制(CCFL)模型,开展了基于压力容器模化本体的下降段CCFL实验研究以及建模分析。通过实验研究获得了不同入口安注水流量、安注水过冷度、堆芯蒸汽流量等条件下的下降段环腔内的安注特性数据,并基于实验数据进行了CCFL建模分析。结果表明,开始发生CCFL的蒸汽无量纲流速与入口安注水无量纲流速呈现正相关,基于无量纲流速建立的模型斜率与入口安注水无量纲流速呈现高度指数关联。本文建立了适用于从不发生CCFL至不完全CCFL,再到完全CCFL的下降段水-蒸汽气液逆流全过程预测模型。

蒸汽-水喷射混合器的设计与应用

介绍了蒸汽-水喷射混合器的工作原理相关的设计计算及其在蒸汽-水热回收系统中的成功应用。该混合器与传统的间接式换热器相比具有系统阻力小和换热效率高的特点,此技术适合于化工加压设备自动或手动控温操作系统的余热回收。

高扬程蒸汽－水喷射器的设计及其应用

探讨了高效率高扬程蒸汽－水喷射器新的设计方法，根据新的思路推导出喷射系数等一系列公式，对各参数的选定和计算作了较详细的说明。

蒸汽喷入低温水中换热过程的数值模拟

利用Fluent模拟得出蒸汽-水直接接触换热过程中流体的温度场和速度场的分布。在此基础上,研究分析了变蒸汽压力、初始水温、喷汽管入口深度、喷汽角以及多孔充汽等工况对蒸汽-水直接接触换热效果的影响。研究表明:喷汽管口位于中间位置处时,无量纲温度最大且换热效果最佳;其次中间下部区域优于中间上部。喷汽角对换热有着双重影响,其最佳值受实际装置和流体物性等众多因素影响可以确定的是在60°和30°附近位置处换热效果最好。

热泵在纸机干燥部蒸汽——冷凝水系统的应用(下)

由于节能效果明显,改善了纸机烘缸温度曲线及控制手段简便等原因,热泵系统在造纸机干燥部的运用越来越普遍。在众多的热泵系统中美国Gardner热泵系统具有高效的汽水分离技术、湿端烘缸的通汽技术、吹贯蒸汽控制技术的特点。

热泵在纸机干燥部蒸汽——冷凝水系统的应用(上)

由于节能效果明显,改善了纸机烘缸温度曲线及控制手段简便等原因,热泵系统在造纸机干燥部的运用越来越普遍。在众多的热泵系统中美国GARDNER热泵系统具有高效的汽水分离技术、湿端烘缸的通汽技术、吹贯蒸汽控制技术的特点。

Hydrogen Production by Low-temperature Steam Reforming of Bio-oil over Ni/HZSM-5 Catalyst

We investigated high catalytic activity of Ni/HZSM-5 catalysts synthesized by the impregnation method, which was successfully applied for low-temperature steam reforming of bio-oil. The influences of the catalyst composition, reforming temperature and the molar ratio of steam to carbon fed on the stream reforming process of bio-oil over the Ni/HZSM-5 catalysts were investigated in the reforming reactor. The promoting effects of current passing through the catalyst on the bio-oil reforming were also studied using the electrochemical catalytic reforming approach. By comparing Ni/HZSM-5 with commonly used Ni/Al2O3 catalysts, the Ni2O/ZSM catalyst with Ni-loading content of about 20% on the HZSM-5 support showed the highest catalytic activity. Even at 450 ℃, the hydrogen yield of about 90% with a near complete conversion of bio-oil was obtained using the Ni2O/ZSM catalyst. It was found that the performance of the bio-oil reforming was remarkably enhanced by the HZSM-5 supporter and the current through the catalyst. The features of the Ni/HZSM-5 catalysts were also investigated via X-ray diffraction, inductively coupled plasma and atomic emission spectroscopy, hydrogen temperature-programmed reduction, and Brunauer-Emmett-Teller methods.

混合蒸汽在板式换热器中的凝结换热特性

本文通过设计搭建板式换热器凝结换热实验台,研究了不同酒精浓度(0%,1%,2%,5%,10%,20%)、不同蒸汽压力(31.2 k Pa,47.4 k Pa,84.5 k Pa)下,定质量流量的酒精-水混合蒸汽在板式换热器中凝结换热系数随冷却水温的变化特性。实验结果表明:随着冷却水温的增大,换热系数随之增大,几乎呈现出线性变化的关系;低浓度的混合蒸汽(1%,2%)明显高于纯水蒸气的换热系数,随着浓度增大,换热系数下降;随着压力增大,换热系数增强。沿蒸汽流动的方向,换热系数是逐渐下降的。

EFFECTS OF LOW-LATITUDE MONSOON SURGE ON THE INCREASE IN DOWNPOUR FROM TROPICAL STORM BILIS

By using the dataset of CMA-STI Tropical Cyclone Optimal Tracks, NCEP/NCAR reanalysis and intensive surface observations, a study is performed of the influences of a low-latitude monsoon surge on the longer persistence and increase in torrential rains from the landing tropical storm Bilis. Results suggest that the southwest monsoon was anomalously active after Bilis came ashore. The westerly winds in Bilis's south side might give rise to the poleward movement of the SW monsoon, thus enlarging the pressure gradient between Bilis and the anticyclonic circulation to the south with the result of greatly intensified SW monsoon, which fueled plentiful water vapor, heat and momentum into the declining Bilis and allowed its long stay over land instead of erosion and disappearance. Before Bilis's landfall, the 2006 East Asian monsoon surge, characterized by the atmospheric ISO, experienced remarkable northward propagation. After landfall, the strong surge and powerful low frequency vapor convergence were just on the south side of Bilis, resulting in sharply increased rainfall. In addition, a broad belt of high-valued vapor fluxes extended from the eastern Arabian Sea via the Bay of Bengal, Indochina Peninsula and the South China Sea into the south of China. The belt was linked with the SW monsoon surge forming a moist tongue stretching from the Bay of Bengal to the south of China, which supplied continuously abundant vapor for Bilis along with the surge propagating poleward.

Hydrogen Production by Catalytic Steam Reforming of Bio-oil, Naphtha and CH4 over C12A7-Mg Catalyst

Hydrogen production by catalytic steam reforming of the bio-oil, naphtha, and CH4 was investigated over a novel metal-doped catalyst of （Ca24Al28O64）^4＋·4O^-/Mg （C12A7-Mg）. The catalytic steam reforming was investigated from 250 to 850℃ in the fixed-bed continuous flow reactor. For the reforming of bio-oil, the yield of hydrogen of 80% was obtained at 750℃, and the maximum carbon conversion is nearly close to 95% under the optimum steam reforming condition. For the reforming of naphtha and CH4, the hydrogen yield and carbon conversion are lower than that of bio-oil at the same temperature. The characteristics of catalyst were also investigated by XPS. The catalyst deactivation was mainly caused by the deposition of carbon in the catalytic steam reforming process.

Conversion of Methane by Steam Reforming Using Dielectric-barrier Discharg

Conversion of methane by steam reforming was carried out by means of dielectric-barrier discharge.A systemic procedure was employed to determine the suitable experimental conditions.It was found that one of the plasma generators can match the system best.A higher power input can always bring a higher conversion,but the selectivity to C2H6 decreased from 52.48% to 39.43% as the power increased from 20W to 49W.When discharge distance was 4mm,selectivities to almost all main products reached the max.The inner electrode made of stainless steel and the outer electrode with aluminum foil were one of the best options which can obviously enhance the conversion of methane.A larger flow rate always resulted in a lower conversion of methane.In the most time,19.93% steam promoted conversion of methane.

Influence of subsequent curing on water sorptivity and pore structure of steam-cured concrete

Steam-cured condition is found to cause larger porosity and worse properties of concrete compared with normal curing condition. For the sake of seeking effective measurements to eliminate this bad effect of steam-cured condition on concrete, the water sorptivity and pore structure of steam-cured concretes exposed to different subsequent curing conditions were investigated after steam-curing treatment. The capillary absorption coefficient and porosity of the corresponding concretes were analyzed, and their mechanisms were also discussed. The results indicate that water sorptivity and pore structure of steam-cured concrete are greatly influenced by the curing condition used in subsequent ages. Exposure steam-cured concrete to air condition has an obviously bad effect on its properties and microstructures. Adopting subsequent curing of immersing steam-cured concrete into about 20℃ water after steam curing period can significantly decrease its capillary absorption coefficient and porosity. Steam-cured concrete with 7 d water curing has minimum capillary absorption coefficient and total porosity. Its water sorptivity is decreased by 23% compared with standard curing concrete and the porosity is 9.6% lower. Moreover, the corresponding gradient of water sorptivity and porosity of steam-cured concrete both decrease, thus mictostructure of concrete becomes more homogeneous.

Binary Adsorption Equilibrium of Benzene-Water Vapor Mixtures on Activated Carbon

Adsorption equilibrium isotherms of benzene in the concentrationrange of 500-4000 mg·m^-3 on two commercial activated carbons wereobtained using long-column method under 30 deg. C and differenthumidity condi- tions. Results show that the benzene and water vaporshave depression effects upon the adsorption of each other and thatthe unfavorable effect of water vapor resembles its single-componentisotherm on activated carbon. A com- petitive adsorption model wasproposed to explore the depression mechanisms of the non-ideal,non-similar binary adsorption systems.

Assessing the kinetic model of hydro-distillation and chemical composition ofAquilaria malaccensis leaves essential oil

This study aimed to model the kinetic of hydro-distillation of Aquilaria malaccensis leaves oil in order to understand and optimize the extraction process. In addition, this study, for the first time, aimed to identify the chemical compositions of the A. rnalaccensis leave-oil. By assessing both first-order kinetic model and the model of simultaneous washing and diffusion, the result indicated that the model of simultaneous washing and diffusion better describes the hydro-distillation mechanism of the essential oil from A. rnalaccensis leaves. The optimum time, solid to liquid ratio, and the heating power for extracting the highest amount of essential oil were found to be around 3 h, 1：10 （g. ml-1）, and 300 W respectively. Yellow essential oil with a strong smell and a yield of 0.05 v/w was extracted by hydro-distillation Clevenger apparatus. Chemical compounds of the essential oil were analyzed using gas chromatography-mass spectroscopy （GC/MS）, which resulted in identification of 42 compounds that constitute 93% of essential oil. Among the identified components, Pentadecanal （32.082%）, 9-Octadecenal, （Z） （15.894%）, and Tetradecanal （6.927%） were the major compounds. Considering the fact that all the identified major components possess pesticidal properties, A. malaccensis leaves can be regarded as a promising natural source for producing pesticides.

Numerical Simulation of Direct-contact Condensation from a Supersonic Steam Jet in Subcooled Water

The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct-contact heat exchangers,was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water.The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter.The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics（CFD） simulations were compared with the published experimental data and fairly good agreement was observed between the two,thus validating the condensation model.The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33,while the condensation heat transfer coefficient varies from 0.75-0.917 MW·（m ^2 ·K）^ -1 for water temperature in the range of 293-343 K.

Supported metal catalysts at the single-atom limit – A viewpoint

An account of recent work on supported single‐atom catalyst design is given here for reactions as diverse as the low‐temperature water‐gas shift,methanol steam reforming,selective ethanol dehydrogenation,and selective hydrogenation of alkynes and dienes.It is of fundamental interest to investigate the intrinsic activity and selectivity of the active metal atom site and compare them to the properties of the corresponding metal nanoparticles and sub‐nm clusters.It is also important to understand what constitutes a stable active metal atom site in the various reaction environments,and maximize their loadings to allow us to design robust catalysts for industrial applications.Combined activity and stability studies,ideally following the evolution of the active site as a function of catalyst treatment in real time are recommended.Advanced characterization methods with atomic resolution will play a key role here and will be used to guide the design of new catalysts.

Feasibility Analysis of Back-Pressure Steam Feeding Water Pump for Direct Air-Cooled Unit

As the performance of an air-cooled condenser is apt to be affected by the fluctuating ambient condition, some difficulties are brought to the use of a steam feeding water pump in an air-cooled unit. This paper introduces a new design of for steam feeding the water pump of an air-cooled unit using the back-pressure steam turbine as the prime motor. Using variable condition analysis on a 600 MW direct air-cooled unit, and with consideration of the effect on the ambient conditions, the feasibility, economy, and adaptability of the design are verified.

Vapor Pressure Measurement of Water+1,3-Dimethylimidazolium Tetrafluoroborate System

In absorption cycles,ionic liquid(IL)1,3-dimethylimidazolium tetrafluoroborate([Dmim]BF4)may be a promising absorbent of working pair using water as refrigerant.The vapor pressures of[Dmim]BF4 aqueous solution were measured with the boiling-point method in the temperature range from 312.25 to 403.60 K and in the mass concentration range of 65%to 90%of[Dmim]BF4.The experimental data were correlated with an Antoine-type equation and the Non-Random Two-Liquid(NRTL)model,and the average absolute deviations between the experimental and calculated values were 1.06%and 1.15%,respectively.For the[Dmim]BF4 aqueous solution,the experimental vapor pressures show negative deviations from the calculated data with Raoult's law.For higher mass concentration of the IL,the deviation is more negative.In addition,the vapor pressures,the hydrophilicity and the solubility of[Dmim]BF4 aqueous solutions were compared with those of[Dmim]Cl aqueous solutions and [Bmim]BF4 aqueous solutions at IL-mole fraction of 0.20.

Modeling a high output marine steam generator feedwater control system which uses parallel turbine-driven feed pumps

Parallel turbine-driven feedwater pumps are needed when ships travel at high speed. In order to study marine steam generator feedwater control systems which use parallel turbine-driven feed pumps, a mathematical model of marine steam generator feedwater control system was developed which includes mathematical models of two steam generators and parallel turbine-driven feed pumps as well as mathematical models of feedwater pipes and feed regulating valves. The operating condition points of the parallel ttu-bine-driven feed pumps were calculated by the Chebyshev curve fit method. A water level controller for the steam generator and a rotary speed controller for the turbine-driven feed pumps were also included in the model. The accuracy of the mathematical models and their controllers was verified by comparing their results with those from a simulator.

Genesis of H-ZSM-11 Acidity under Hydrogen and Water Vapor Treatment

1. Introduction Zeolites are widely used in acid heterogeneous catalysis [1, 2]. Due to the unique physical and chemical properties ofzeolites, they are widely used in commercial catalytic processes, such as fluidized catalytic cracking, hydrocracking, methanol conversion to gasoline or olefins, ethylbenzene production, xylene isomerization, aromatics hydrogenation [3-9]. Acidity, high thermal stability, and shape selectivity determine the use of zeolites as catalysts in reaction processes through acid mechanisms [ 10].