气相声速测量偏差对导出热力学性质的影响

气相声速是测量准确度最高的热物性之一,并可以导出理想气体比定压热容和第二维里系数等其他热力学性质。分析了定程干涉法中存在的系统偏差,建立了绝对系统偏差（δ_FAE）和相对系统偏差（δ_FFE）对导出热力性质影响的数学模型,并开展了模拟计算。研究结果表明,理想气体比热容比受绝对系统偏差的影响为2δ_FAE,但是绝对系统偏差对多原子气体的理想气体比定压热容的影响大,可高于-100δ_FAE,且温度越高,影响越大;相对系统偏差主要影响声速维里系数,在温度和相对系统偏差相同时,不同工质的第二声速维里系数的绝对变化量相同。绝对系统偏差和相对系统偏差在导出第二维里系数中的影响较小。     

气相声速测量偏差对导出热力学性质的影响

气相声速是测量准确度最高的热物性之一,并可以导出理想气体比定压热容和第二维里系数等其他热力学性质。分析了定程干涉法中存在的系统偏差,建立了绝对系统偏差(δFAE)和相对系统偏差(δFFE)对导出热力性质影响的数学模型,并开展了模拟计算。研究结果表明,理想气体比热容比受绝对系统偏差的影响为2δFAE,但是绝对系统偏差对多原子气体的理想气体比定压热容的影响大,可高于-100δFAE,且温度越高,影响越大;相对系统偏差主要影响声速维里系数,在温度和相对系统偏差相同时,不同工质的第二声速维里系数的绝对变化量相同。绝对系统偏差和相对系统偏差在导出第二维里系数中的影响较小。     

单原子气体第二介电维里系数准确计算

采用当前文献中已知最佳的从头算势能和极化率计算了多种稀有气体的第二介电维里系数。研究对象包括氦-4、氦-3、氖和氩。根据经典统计力学公式和一二阶量子修正项对第二介电维里系数进行了计算,在此基础上,通过[1/1]帕德近似将研究的温度下限拓展至25 K。第二介电维里系数理论值的不确定度可以由势能和极化率的不确定度进行评估,再结合与文献实验数据的比较可以发现,理论计算结果为计量、仪器标定等领域提供了所需的高精度基础数据。     

加压下甲醇-水二元体系汽液平衡数据的测定及关联

用加压静态平衡釜测定了甲醇-水二元体系在353.15、373.15、388.15和403.15K下的汽液平衡数据。除373.15K外,其他3个温度点的数据未见文献报道,实验数据用含第二维里系数的截尾维里方程和5个活度系数方程关联。结果表明,所选计算模型均能很好地拟合实验数据,尤以维里方程加上Margules方程拟合精度最高。     

以［Li（TX-7）］SCN/H2O为工质对的第二类热泵特性研究

通过静态法测量了[Li（TX-7）]SCN/H₂O溶液在283.15~443.15 K温度条件下的饱和蒸气压,通过差式扫描量热法测量了离子液体[Li（TX-7）]SCN在温度T=73.15~423.15 K条件下的比热容,并建立了经验关联式,通过Wilson模型对[Li（TX-7）]SCN/H₂O溶液组分活度系数的关联预测了其过量焓,并通过预测值计算了二元溶液的比焓,建立了[Li（TX-7）]SCN/H₂O的热力学模型。基于实验数据与热力学模型对以[Li（TX-7）]SCN/H₂O为工质对的第二类热泵的理论循环特性进行了仿真分析,研究了各部件不同工作温度对系统性能参数的影响,并与其他吸收式系统的性能参数进行了比对。[Li（TX-7）]SCN/H₂O系统的性能优于LiBr/H₂O系统,适用于发生温度和蒸发温度较低的工况。     

小角激光光散射法订定聚砜的特性粘数——分子量关系式

用小角激光光散射法、高效凝胶色谱法和粘度法研究了双酚A与4,4′-二氯二苯砜的缩聚物-聚砜的稀溶液性质,订定了聚砜在1,2-二氯乙烷、三氯甲烷和四氢呋喃中的特性粘数-分子量关系式。根据Stockmayer-Fixman的理论计算了聚砜分子链的无扰尺寸[(r_0~2)/M]~(1/2)、溶剂与高分子间的相互作用参数B和X_1以及第二维里系数A_2与分子量的关系。     

活化气氛对CO2加氢制取低碳烯烃Fe-K催化剂构-效关系

CO₂加氢直接制取低碳烯烃是实现其资源化利用的重要途径。通过热分解法制备了5种不同K含量（1%、3%、5%、7%、9%）的Fe-K催化剂用于CO₂加氢反应,结果表明Fe95-K5（95% Fe-5% K,质量分数）催化剂具有最优的活性及C₂～C₄烯烃选择性;随后对Fe95-K5催化剂进行了10% H₂/Ar、10% CO/Ar及5% CO/5% H₂/Ar 3种不同气氛活化处理以及CO₂加氢反应。结果发现,10% CO/Ar活化的催化剂具有最高的C₂～C₄烯烃选择性（38.1%）及链增长能力（α=0.644）。此外,还通过X射线衍射、Raman、程序升温等表征技术揭示了催化剂在不同活化气氛下的结构演变历程。研究发现,10% CO/Ar与5% CO/5% H₂/Ar活化的催化剂会生成γ₁型碳化铁结构,而10% H₂/Ar活化的催化剂则会在反应过程中生成γ₂型碳化铁结构,两种碳化铁结构对CO₂解离均有促进作用。     

液态和超临界态二氧化碳的非线性声学性质

根据美国国家标准局提供的二氧化碳在液态和超临界态下的声速、密度、比定压热容、膨胀系数等物理参数数据库中数据,计算了二氧化碳在液态和超临界状态下的声速压力系数、声速温度系数和非线性声参量几个非线性声学参数。分析归纳了液态二氧化碳和超临界二氧化碳的非线性声学特性,对比分析了液态二氧化碳、超临界二氧化碳和一般有机液的非线性声学特性。详细分析了二氧化碳在临界点附近的非线性声学特性。研究表明,液态二氧化碳表现出类似于一般液体在常温常压下的非线性声学特性;超临界二氧化碳的声速压力系数、声速温度系数和非线性声参量值可为正值或负值,其值随压力或温度的变化具有一定的规律性。压力越大温度越低,超临界二氧化碳的非线性声学特性越接近液态二氧化碳或一般液体。在临界点附近区域,3个参量值随压力或温度的变化出现正负最大值间的跳跃变化。     

硬球-拟颗粒模拟高超声速稀薄气体流动

发展了适应高超声速稀薄流动的硬球-拟颗粒模拟(HS-PPM)，并分别采用硬球分子动力学模拟(HS)、HS-PPM和直接模拟蒙特卡洛(DSMC)对马赫数为5、努森数为0.8的圆球绕流进行模拟，证明了HS-PPM可以得到更接近HS的模拟结果。对雷诺数100、马赫数5~19的三维圆球绕流，采用HS-PPM模拟得到了填充率0.01~0.08、完全热边界和完全滑移边界条件下的曳力系数，与HS模拟结果的一致性较好；模拟了马赫数24、努森数0.11~4.55的零攻角三维尖锥绕流，结果与文献中DSMC的模拟结果相符。研究验证了HS-PPM处理高超声速稀薄气体流动的可行性。     

基于相对声速系数的聚合物薄板表面内应力测量方法

介绍一种聚合物薄板制品表面内应力的测量方法,基于声弹性理论研究聚合物薄板制品表面内应力与瑞利波速度的相互关系。在此基础上提出相对声速系数δ表征法,以无应力状态下的瑞利波速度作为比较基准,即将实时测量的有应力状态的瑞利波速度与无应力状态时的瑞利波速度的差值与之相对比较,通过声速的相对系数,来确定应力存在大小的相对值,以此回避难以测量的聚合物制品的声弹性系数,从而实现聚合物薄板制品的表面内应力相对分布的快速精确测量。通过自制的拉伸实验装置进行了验证,相对声速系数系数δ法得到的实验测量结果与通过应变片测量的结果具有一致性。     

An extension of the group contribution method for estimating thermodynamic and transport properties. Part III. Noble gases

Earlier work on the group contribution method applied to the Kihara potential is extended to noble gases for the estimation of second virial coefficients, dilute gas viscosities and diffusivities with a single set of gas group parameters. Group parameters are determined when second virial coefficient and viscosity data of pure gases are satisfactorily fitted within the experimental uncertainties. Parameters for gas groups (He, Ne, Ar, Kr and Xe) are found to provide good predictions of mixture properties: second virial cross coefficients, mixture viscosities, and binary diffusion coefficients. Application of the model shows that second virial coefficient data are represented with good results comparable to the values by means of the corresponding states correlation. The reliability of the present model in viscosity predictions is proved by comparison with the Lucas method. Prediction results of diffusivity are in excellent agreement with literature data and compare well with values obtained by means of the Fuller method.     

Vapor-liquid equilibria for the binary monoethanolamine+ water and monoethanolamine+ethanol systems

Isobaric vapor-liquid equilibrium data for monocthanolamine (MEA)+water and monoethanolamine (MEA)+ ethanol were measured in an equilibrium cell circulating both the vapor and liquid phases. The measurements of the boiling temperatures and corresponding equilibrium compositions for two binary mixtures were carried out at the atmospheric pressure. The results were checked for thermodynamic consistency by the point test method. The activity coefficients for nonideality of the liquid phase were calculated by using the Wilson, NRTL, and UNIQUAC equations. The fugacity coefficients for nonideality of the vapor phase were calculated from the virial equation of state with the second virial coefficient. The experimental data were verified to be thermodynamically consistent and showed a good agreement with the calculated values.     

Second virial coefficients of polar gases — a correlation with stockmayer potential function

The parameters of the Stockmayer potential function were calculated by a least-squares analysis of the second virial coefficient data for 66 polar substances. By using these parameters, the second virial coefficient of these tabulated materials can be calculated with a mean standard deviation of 20.2 cm³ mole^?1 or 3.2%. The possibility of extrapolating second virial coefficients from high to low temperatures is also demonstrated.     

Equation of state for gaseous nitrogen determined from isotropic model potentials

A four‐term virial equation of state was combined with isotropic potential models to predict accurate volumetric and caloric thermodynamic properties of nitrogen in the gas phase. The parameters of the model potentials were determined from a fit to acoustic data alone; no other data was used. For nitrogen, it was only necessary to approximate the fourth virial coefficient at the level of interactions that contained no more than one triplet potential; higher order approximations offered no further advantage. It was shown that the four‐term virial equation was more accurate than the three‐term analogue. It was found that predicted virial coefficients became consistent with experimental values when temperature was >150 ± 30 K; conversely, below this range virial coefficients predicted by the model did not agree with experiment. It was believed that predicted fourth virial coefficient was reliable and accurate only above about 150 K. Predicted compressibility factors deviated by <0.05% at pressures of up to 10–12 MPa, or densities up to 4 mol/dm³ (≈0.4ρ_c), only when temperature was >220 K. Values of enthalpy predicted from the equation of state showed good agreement with experimental data.     

Vapor Pressure,Vaporization Enthalpy,Standard Enthalpy of Formation and Standard Entropy of n-Butyl Carbamate

The vapor pressures of n-butyl carbamate were measured in the temperature range from 372.37 K to 479.27 K and fitted with Antoine equation. The compressibility factor of the vapor was calculated with t...     

An extension of the group contribution method for estimating thermodynamic and transport properties part II. Polyatomic gases (F2, Cl2, CS2, H2S, NO and N2O)

Earlier work on the group contribution method applied to the Kihara potential is extended to polyatomic gases for the calculation of second virial coefficients, viscosities and diffusivities of dilute gases with a single set of gas group parameters. Functional group parameters are evaluated from the simultaneous regression of second virial coefficient and viscosity data of pure gases. Parameters for gas groups (F₂, Cl₂, CS₂, H₂S, NO, nd N₂O) are found to provide good predictions of second virial cross coefficients, mixture viscosities and binary diffusion coefficients of gas-gas mixtures. Application of the model shows that second virial coefficient data can be represented with good results comparable to the values by means of the corresponding states model. The reliability of the present model in viscosity predictions is proved by comparison with the Lucas method. Predictions of binary diffusion coefficients are in excellent agreement with experimental data and compare well with values obtained by means of the Fuller method.     

Study of the distribution of the molecular orientation in thick polyethylene samples by X-ray diffraction, infra-red dichroism and Raman spectroscopy

The molecular orientation in thick polyethylene samples has been studied by wide-angle X-ray diffraction, i.r. dichroism and Raman spectroscopy. The original specimens, with dimensions of the order of a centimetre, were cut to obtain 1 mm thick platelets on which the measurements were made. The mean coefficient of the second-order Legendre polynomial, P₂, was calculated from X-ray diffraction and from the 1894 cm⁻¹ i.r. band for the crystalline phase, from the 909 cm⁻¹ i.r. band for the vinyl end groups and from the 1130 and 1060 cm⁻¹ Raman bands for the all-trans C-C conformers. The fourth-order coefficient, P₄, was also determined from X-ray diffraction and Raman spectroscopy for a series of cylindrical rods of draw ratios (λ) ranging from 6 to 20. An excellent correlation is observed between the P₂ coefficients measured from different X-ray reflections and from the 1894 cm⁻¹ i.r. band. The Raman spectroscopy results show that the all-trans bonds located in the amorphous phase are aligned perpendicular to the extrusion direction for the λ = 6 rod, and gradually reorient towards the fibre axis for λ values up to 20, while the P₂ and P₄ coefficients calculated for the crystalline phase remain constant at λ ≥ 12. The variation of the orientation through the thickness of the samples was investigated for the cylindrical rods and for an H-shaped moulding produced by extrusion and rolling. Minor differences in the degree of molecular orientation were detected between the centre and the surface of the rods, whereas important variations were measured for the H-shaped sample.     

Properties of ceramic foam catalyst supports: mass and heat transfer

Mass and heat transport properties have been determined for 30 PPI -Al₂O₃ ceramic foam containing 6 wt.% γ-Al₂O₃ washcoat. The foam was loaded with 5 wt.% platinum and the rate of carbon monoxide oxidation measured for a 0.3 cm cylindrical segment of the foam operating with mass transfer controlling at 550 °C. This gave a mass transfer factor versus Reynolds number correlation that was equivalent to a packed bed of particles.

A correlation for the radial heat transfer coefficient in a bed of ceramic foam was determined by measuring outlet temperatures achieved when air at varying flow rates and inlet temperatures was passed through a bed of foam pellets. Correlation parameters of a 1D model were fitted from 700 to 1000 °C using a Simplex optimization routine. Radial heat transfer coefficients were two to five times higher than those predicted from packed bed correlations.     

第二维里系数与温度的关联及Lennard-Jones和Stockmayer位能参数的推算

对第二维里系数与温度的经验关联式作了评选,推荐B=B_0+B_1/t+B_2/t~2+B_3/t~3+B_4/t~4,t=T/1000,和lg(-B)=E_0+E_1(100/T)+E_2lg(T/100),对166种纯物质作了关联.利用上述物质的第二维里系数数据推算其Lennard-Jones位能参数值和41种极性物质的Stockmayer位能参数值.