乙酸在水和乙醇、水和N,N-二甲基甲酰胺混合溶剂中电离焓研究

本文用LKB-2277 BioActivity Morator测定了298.15K时乙酸在水和乙醇,水和N,N二甲基甲酰胺(DMF)两种混合溶剂中电离焓。并用溶液中溶质与溶剂相互作用的观点,对乙酸在上述两种混合溶剂中电离焓的区别及变化趋势进行了简单的讨论。     

CO2分压对碳钢腐蚀的影响及缓蚀性能研究

为了研究CO2分压对碳钢腐蚀的影响及缓蚀剂的缓蚀性能,在模拟油田腐蚀环境中,采用FS-Ⅲ高温高压动态腐蚀仪,辅以失重法计算,对不同CO2分压下油管钢N80的动态腐蚀速率,A（1-硫脲乙基-2-烷基咪唑啉）和B（1-氨乙基-2-烷基咪唑啉季铵盐）两种咪唑啉缓蚀剂对CO2腐蚀的缓蚀效果及与其它油田用化学药剂的配伍性进行了研究。结果表明,在实验温度条件下,随着CO2分压的升高,N80钢的动态腐蚀速率呈现先增大后减小的变化趋势 缓蚀剂A和B对CO2腐蚀都有很好的抑制效果,最佳缓蚀效率分别为95%和94.6%,其中A与其它化学药剂具有很好的配伍性。使用缓蚀剂A对油田CO2腐蚀进行防护会有很好的效果。     

Numerical study on convective heat transfer of supercritical CO2 in vertically upward and downward tubes

The experimental measurement of supercritical pressure carbon dioxide(sCO_2) heat transfer in vertical downward flow was performed in a circular tube with inner diameter of 10 mm. Then, a three-dimensional numerical investigation of sCO_2 heat transfer in upward and downward flows was performed in a vertical heated circular tube. The influence of heat flux, mass flux,and operating pressure on heat transfer under different flow directions were discussed. According to the "pseudo-phase transition" viewpoint to supercritical fluids, the analogy to the subcritical inverted-annular film boiling model, the physical model to sCO_2 heat transfer was established, where fluid region at the cross-section of circular tube was divided into gas-like region covering heated wall and core liquid-like phase region. Then, the thermal resistance mechanism which comprehensively reflected the effect of multiple factors including the thickness of the gas-like film or liquid-like region, fluid properties and turbulence on heat diffusion was proposed. Surprisingly, thermal resistance variation in upward flow is well identical with that of wall temperature and heat transfer deterioration is predicted successfully. In addition, compared with thermal resistance in the core liquid-like region, gas-like film formation is determined to be the primary factor affecting heat transfer behavior. Results also show that total thermal resistance in upward flow is always larger than that in downward flow. The investigation can provide valuable guide to design and optimize sCO_2 heaters.     

超细铜基催化剂上CO_2加氢合成甲醇催化性能研究

用溶胶-凝胶法制备得到超细Cu-ZnO/TiO2-SiO2催化剂。考察了在CO2加氢合成甲醇反应中,还原温度、反应温度、反应压力和体积空速对催化剂活性和选择性的影响。确定了该体系催化剂的适宜反应工艺条件,并对催化剂组成与催化活性的关系进行了研究。     

H_2/H_∞鲁棒控制器设计的线性矩阵不等式方法

对于一类同时具有H2和H∞性能指标约束的线性系统,基于线性矩阵不等式处理方法(LMI),设计了系统的状态反馈控制器。通过LMI工具箱提供的求解器,可以方便、有效地得到所求控制器的参数化表示。仿真结果表明了混合H2/H∞控制对干扰抑制的有效性。     

三元体系Na_2CO_3-K_2CO_3-H_2O 298 K 相关系和溶液物化性质的研究

用等温溶解平衡法研究了三元体系Na2CO3-K2CO3-H2O 298K时的相平衡关系和平衡溶液的物化性质(密度、折光率、粘度、pH值).该三元体系为复杂三元体系,形成了一种新的复盐Na2CO3.K2CO3.H2O.用经验公式对平衡液相的密度、折光率进行了计算,计算值与实测值吻合得较好.     

Effect of Cl~- Concentration on the Corrosion Behavior of 16Mn Steel in Saturated H_2S/CO_2 Solution

The corrosion behavior of 16Mn steel was studied in saturated H_2S or H_2S/CO_2 solutions containing different Cl~-concentrations at 80℃.The microstructure and chemical composition of the corrosion products were investigated through scanning electron microscopy,energy-dispersive X-ray spectroscopy,EPMA,and X-ray diffraction.Results showed that the corrosion rate decreased with increasing Cl~-concentration in saturated H_2S or H_2S/CO_2 solution at pH 4.Conversely,the corrosion rate increased with increasing Cl~-concentration in saturated H_2S solution at pH 6.The relative H~+concentration decreased because of the increase of Cl~-concentration at pH 4,and Cl~-acted as a catalyst in the corrosive medium at pH 6 because the net H~+concentration decreased obviously compared with the condition at pH4.Cl~-promoted the formation of Fe-deficient iron sulfide at pH 4,and the opposite effect was observed in the nearly neutral solution.The corrosion rate increased firstly with increasing Cl~-concentration and then decreased in the saturated H_2S/CO_2solution at pH 6.The corrosion products were mainly composed of two kinds of iron sulfide.Sulfide FeS_(1-x) was a kind of tetragonal crystal,whereas the other was the hexagonal/monoclinic iron sulfide Fe_(1-x)S.The corrosion film that was mainly composed of FeS_(1-x) did not confer a protective effect on the base metal.The atomic ratio of Fe/S was more than 1 for FeS_(1-x).The appearance of sulfide FeS_(1-x) resembled a square block or small,needlelike,flocculent particles.The atomic ratio of Fe/S was less than 1 for Fe_(1-x)S,and the corrosion film mainly composed of Fe_(1-x)S conferred some protective property on the base metal.The sulfide FeS_(1-x) exhibited a long claviform morphology with a hexagonal or quadrilateral cross-sectional shape.     

Experimental investigations on the heat transfer characteristics of micro heat pipe array applied to flat plate solar collector

This paper introduces a novel flat plate solar collector(FPC) using micro heat pipe array(MHPA) as a key element.To analyze the thermal transfer behavior of flat plate solar collector with micro heat pipe array(MHPA-FPC),an indoor experiment for thermal transfer characteristic of MHPA applied to FPC was conducted by using an electrical heating film to simulate the solar radiation.Different cooling water flow rates,cooling water temperatures,slopes,and contact thermal resistances between the condenser of MHPA and the heat exchanger were tested at different heating powers.The experimental results indicate that MHPA-FPC exhibits the enhanced heat transfer capability with increased cooling water flow rate and temperature.Total thermal resistance has a maximum decline of approximately 10% when the flow rate increases from 180 to 360 L h 1 and 38% when the cooling water temperature increases from 20℃ to 40℃.When the inclination angle of MHPA-FPC exceeds 30°,the slope change has a negligible effect on the heat transfer performance of MHPA-FPC.In addition,contact thermal resistance significantly affects the heat transfer capability of MHPA-FPC.The total thermal resistances lowers to nearly half of the original level when contact material between the condenser of MHPA and the heat exchanger changes from conductive silicone to conductive grease.These results could provide useful information for the optimal design and operation of MHPA-FPC.     

H_2/CO_2 Gas Transport Performance in Poly(Ethylene Oxide) Reverse-selective Membrane with Star-like Structures

A series of poly(ethylene oxide)(PEO) membranes with star-like structures for CO_2/H_2 separation were prepared by the photo-polymerization method. The structure of PEO membrane was characterized by Fourier transform infrared spectroscopy(FTIR). The thermal property and inter-segmental distance of polymer chain were investigated by differential scanning calorimetry and wide-angle X-ray diffraction, respectively. The density was determined by hydrostatic weighing method. The gas permeability, solubility and diffusivity of CO_2 and H_2 were investigated in the star-like PEO membranes. The relationship between gas permeation performances and physical properties was also discussed. The membrane exhibits outstanding CO_2 permeability(about 9.7×10~(-11) cm~3(STP) cm/cm~2/s/Pa) and CO_2/H_2 selectivity(about 11) compared with other membranes.     

Experimental and numerical investigations on convective heat transfer of dual piezoelectric fans

An investigation is performed to study the convective heat transfer performance under dual piezoelectric fans. Three main aspects are involved in the current study. Firstly, vibration tests for dual specific piezoelectric fans actuating at the first-mode resonant frequency are conducted to illustrate the influence roles of vibrating phase difference and fan-to-fan pitch on the piezoelectric fan vibration amplitude. Secondly, heat transfer measurements are made to compare the heat transfer among single fan, dual fans in-phase and dual fans out-of-phase. Thirdly, three-dimensional numerical simulations are conducted to reveal the influence mechanism of dual piezoelectric fans on heat transfer. The results show that, the vibrating phase difference of dual fans has nearly no influence on the displacement velocity and amplitude of piezoelectric fan related to single fan once the dimensionless pitch (P/W) is beyond 1.2. The dual piezoelectric fans produce nearly the same peak heat transfer coefficient as that of single fan case. Of particular is that the dual fans operating in-phase produce more favorable heat transfer than the dual fans operating out-of-phase, especially in the gap zone between dual fans. Due to the interaction between dual fans, the streaming flow induced by one vibrating fan suffers the action of sweeping flow of another vibrating fan when they operate out-of-phase. While for the dual fans operating in-phase, the streaming flows induced by vibrating fans merge together to form stronger wall jet flow in the region between two fans.     

基于超临界CO_2技术土体脱水效果及影响因素分析

为了解超临界CO_2技术对土体脱水技术可行性,通过对高岭土和膨润土土样在是否超临界状态下进行的脱水试验分析,研究压力、温度和CO_2流量等因素对土体脱水效果的影响.结果表明:试验温度对超临界CO_2干燥过程有显著影响,而压力和CO_2流量对干燥过程的影响相对较小;高岭土土样在超临界CO_2条件下,其自由水脱除效果相比非超临界条件约高1倍;自由水脱除约54.1%,结合水脱除约57.8%,说明超临界CO_2条件下土体脱除结合水效果更明显.     

Numerical investigation on flow and convective heat transfer of aviation kerosene at supercritical conditions

In this paper,characteristics of flow and convective heat transfer of China RP-3 kerosene in straight circular pipe were numerically studied.Navier-Stokes equations were solved using RNG k-turbulence model with low Reynolds number correction.The thermophysical and transport properties of the China RP-3 kerosene were calculated with a 10-species surrogate and the extended corresponding state method(ECS) combined with Benedict-Webb-Rubin equation.The independence of grids was first studied and the numerical results were then compared with experimental data for validation.Under flow conditions given in the paper,the results show that deterioration of convective heat transfer occurs when the wall temperature is slightly higher than the pseudo-critical temperature of kerosene for cases with wall heat flux of 1.2 and 0.8 MW/m 2.The degree of the heat transfer deterioration is weakened as the heat flux decreases.The deterioration,however,does not happen when the heat flux on the pipe wall is reduced to 0.5 MW/m 2.Based on the analysis of the near-wall turbulent properties,it is found that the heat transfer deterioration and then the enhancement are attributed partly to the change in the turbulent kinetic energy in the vicinity of pipe wall.The conventional heat transfer relations such as Sieder-Tate and Gnielinski formulas can be used for the estimation of kerosene heat convection under subcritical conditions,but they are not capable of predicting the phenomenon of heat transfer deterioration.The modified Bae-Kim formula can describe the heat transfer deterioration.In addition,the frictional drag would increase dramatically when the fuel transforms to the supercritical state.     

H_20在电极反应式中的应用

在电极反应式配平中 ,如电极反应左右两边氧原子个数不相等时 ,可用H2 O来平衡。讨论了H2 O在电极反应式配平中的使用条件及方法     

Current research into the use of supercritical CO_2 technology in shale gas exploitation

The use of supercritical CO_2 for shale gas extraction is a promising new technology. This paper explores current research into this process, looking at analysis of the mechanism of CH_4 displacement in nanoporous shale, the positive and negative effects accompanying its use for sequestration as well as organic extraction, the migration of elements and the swelling process, and the macro and micro control mechanisms involved in permeability enhancement in reservoirs. Fruitful directions for future research are also considered through comparison with hydraulic fracturing. The research findings indicate that Sc CO_2 fluid replacement can be used to increase gas production and seal up greenhouse gases as an effective, clean and safe method of shale gas exploitation. It is particularly effective for promoting the desorption of CH_4 in shale reservoirs that have developed fine neck-wide body pores, and the subtle structural changes effected by Sc CO_2 fluid in sensitive minerals in reservoirs with a high brittle mineral content also have a positive effect on permeability and storage capacity. The adsorption process has been characterized as consisting of three stages: short-term shrinkage, slow swelling, and stability; an expansion equation has been proposed for CO_2/CH_4 that incorporates competitive adsorption, collision desorption, and impingement re-adsorption. Sc CO_2 fracturing has been found to be more effective than hydraulic fracturing for dense reservoirs and more effective at linking up pore-micro-fissure-fracture systems.     

毛细抽吸两相回路蒸发器管内传热的理论分析

在建立物理模型和分析管内流动状态并列出基本流协方程的基础上,采用一个二维计算模型进行数值计算,求得管内汽－液相的速度和压力分布。在进一步求解能量方程的基础上,获得其温度分布特性,并与试验结果作了比较,表明有较好的一致性。     

Autoignition of butanol isomers/n-heptane blend fuels on a rapid compression machine in N2/O2/Ar mixtures

Ignition delay times of butanol isomers/n-heptane mixture were measured using a rapid compression machine at compressed pressures of 15,20 and 30 bar,in the compressed temperature range of 650–830 K and equivalence ratio of 1.0.Sensitivity analysis and reaction fluxes analysis were performed using a detailed mechanism of blend fuels so as to evaluate the impact of n-heptane addition and temperature variation on the ignition and combustion process.Over the experimental conditions in this study,the blend fuels displays apparent low and high temperature reactions and a negative-temperature-coefficient(NTC)behavior.With increasing butanol isomers mole fraction in the mixtures,the ignition delay times increase.It is worth noting that the suppression to n-heptane ignition from tert-butanol is very limited.The ignition delay time of 40/60 tert-butanol/n-heptane mixture is smaller than other three kinds of blends.With the increasing of tert-butanol mole fraction,the increasing range of its ignition delay time is very large.Moreover,compressed pressure has a limited effect on the ignition of blend mixture at low temperature but certain influence at medium temperature arrange.Tert-butanol/n-heptane mixture is not sensitive to the pressure.The chemical analysis indicates that butanol isomers also present the NTC behavior because of the low temperature reactivity radicals pool produced by n-heptane.Reaction fluxes analysis shows that the n-heptane addition has little impact on the reaction path.Sensitivity analysis shows that for the pure n-butanol,2-butanol and iso-butanol fuel,H-abstraction from the?-carbon plays the dominant role in the reactions having the inhibiting effect on the low-temperature branching,while the H-abstraction from the?-carbon can promote the ignition;for tert-butanol/n-heptane mixtures,reaction R16.H2O2(+M)=OH+OH(+M)plays the leading role.For n-butanol/n-heptane,iso-butanol/n-heptane mixtures,the major promoting reactions include some H-abstraction from n-heptane and OH branching reactions,the influence of H-abstraction from?-carbon is weaken;For 2-butanol/n-heptane,tert-butanol/n-heptane mixtures,R16 plays an absolutely dominant role,while the major inhibiting reactions add some elementary reactions of small radicals.     

低温重力热管传热性能的理论与实验研究

为给重力热管在低温区的应用提供理论依据,以液氮作为工质对其稳态传热特性进行了实验研究.分别对冷凝段、蒸发段液膜和液池进行分析,建立了综合的数学模型.根据质量和能量守恒方程迭代计算得到了液池高度和液膜沿管长的分布.在液池模型中,通过假设空泡系数的分布,基于其他实验研究的结论提出了自然对流与核态沸腾换热面积公式.当工质液体体积与重力热管总体积的比值为13.5%和15.2%时,计算值与实验值吻合较好.理论和实验研究结果均表明,在蒸发段内液膜和液池的位置对蒸发段壁温的分布有较大的影响.     

Preparation and characterization of ultrananocrystalline diamond films in H_2/Ar/CH_4 gas mixtures system with novel filament structure

Diamond films were prepared by hot filament chemical vapor deposition(HFCVD) in a gas mixtures system of methane, argon and hydrogen. The composition and morphology in different deposition pressures and filament structures were investigated, as well as the friction and wear-resistant properties. The sp3-bonded content was measured and nano-mechanics properties were also tested. Results of atomic force microscopy and X-ray photoelectron spectroscopy show that the diamond films whose surface roughness is less than 10 nm and sp3-bonded content is greater than 70% can be prepared by bistratal filament structure with optimized proportion of Ar. It is also shown that the friction coefficient of diamond films is 0.13 and its wear-resistant property is excellent. Nano-mechanics of films shows that its elastic modulus is up to 650 MPa and hardness can reach higher than 60 GPa. The diamond films with excellent performance have a broad application prospect in microelectromechanical systems(MEMS).     

Theoretical and experimental advances on heat transfer and flow characteristics of metal foams

Open cell metal foam can be applied to greatly improve thermal performance of heat sink and heat exchanger, so that it has been widely used in the fields o     

O2/CO2气氛下单相介质换热器的仿真模型研究

基于O2/CO2燃烧方式的烟气成分和换热特点,建立了O2/CO2气氛下单相介质换热器的动态数学模型,并开发了通用化的仿真算法模块.以某300 MW富氧煤粉燃烧锅炉概念设计中的过热系统为研究对象,进行了减温水、入口烟温扰动下的仿真试验,结果表明O2/CO2=30/70气氛下过热系统的动态特性与空气气氛的变化趋势一致,但汽...