Thermophysical Properties of Binary and Ternary Fluid Mixtures from Dynamic Light Scattering

Several thermophysical properties of R507, a binary refrigerant mixture, and R404A, a ternary mixture, have been determined by dynamic light scattering (DLS), in both the liquid and the vapor states, along the saturation line approaching the vapor–liquid critical point. Data for the thermal diffusivitya and sound speed c _S cover a range of temperatures down to 270K, and data for the surface tension and kinematic viscosity down to 230K. For both mixtures the behavior of all properties determined can be correlated well by the mass-weighted sum of the respective pure component data, when all data are represented as a function of the reduced temperature.     

Thermophysical Properties of the Refrigerant Mixtures R410A and R407C from Dynamic Light Scattering (DLS)

Dynamic light scattering (DLS) has been used for the measurement of several thermophysical properties of the refrigerant mixtures R410A and R407C. Thermal diffusivity and sound speed have been obtained by light scattering from bulk fluids for both the liquid and vapor phases under saturation conditions over a temperature range from about 290 K up to the liquid-vapor critical point. By applying the method of DLS to a liquid-vapor interface, also called surface light scattering (SLS), the saturated liquid kinematic viscosity and surface tension can be determined simultaneously. These properties have been measured for R410A and R407C from about 240 to 330 K and 240 to 350 K, respectively. The results are discussed in detail in comparison with literature data and with a simple prediction method based on the mass-weighted properties of the pure components expressed as functions of the reduced temperature.     

Critical Light Scattering in Pure Liquids

Light-scattering experiments near the critical point (T _c, _c) in fluid systems and, in particular, the central Rayleigh peak in the frequency spectrum are reviewed. Within a nonasymptotic renormalization-group theory, the crossover function is calculated between several regions: (i) from the background to the asymptotic region, (ii) from the hydrodynamic region (wave lengthcorrelation length) to the critical region (wave lengthcorrelation length), and (iii) from critical densities to noncritical densities. Contrary to the mode-coupling expression, the appropriate scaling function is well defined in all limits of its arguments. At T _c the crossover in the wave-vector dependence of the linewidth is also considered. Theoretical results are compared with experiments for pure liquids. Nonuniversal parameters are chosen consistent with the transport coefficients (i.e., the shear viscosity) for the same substance which can be evaluated within the same formalism.     

Viscosity and Surface Tension of Saturated Toluene from Surface Light Scattering (SLS)

It is demonstrated that dynamic light scattering (DLS) on a horizontal gas– liquid interface can be used for the reliable determination of surface tension and liquid kinematic viscosity. In contrast to the more usual approaches of surface light scattering (SLS) spectroscopy, a setup is used and described here which makes it possible to measure the capillary wave propagation characteristics in the forward scattering direction at variable wave numbers. The experiments in this work rely on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). Surface tension and liquid viscosity data of the important and, thus, well-documented reference fluid toluene have been measured under saturation conditions over a wide temperature range, from 263 to 383 K. These data demonstrate the excellent performance of the surface light scattering technique. The achievable accuracy of this technique is discussed in detail for both properties in connection with reference values available in the literature.     

动态光散射在颗粒检测中的应用

动态光散射是常用的一种用于检测颗粒粒径分布的方法。本文详细介绍了该技术在测量颗粒粒径、介电常数、传导率、旋转扩散系数、环境的影响以及结晶条件等方面的研究进展,并对该技术的发展及应用做出了进一步的讨论,提出了动态光散射方法存在的问题,以及克服动态光散射的背景噪声、提高光源质量以及建立更智能化的算法等研究方向。     

双温度法改进动态光散射仪测量精度研究

提出了双温度法来提高动态光散射法测量纳米颗粒粒径的测量精度。在详细分析了动态光散射法中各种误差来源的基础上,总结出大多误差来源与样品池的温度变化无关,讨论了温度对溶液的黏滞系数及系统的扩散系数影响,在此基础上提出了双温度法剔除与样品池温度无关的噪声来源,从而改善动态光散射的测量精度。实验结果证明了改方法的可靠性。     

Ten Years of Parameter Estimation Applied to Dynamic Thermophysical Property Measurements

The parameter estimation theory is considered the best way to estimate thermophysical properties from dynamic experiments. This approach deals with measurement and model errors in a statistical context and provides useful information to optimize the experiment. The experience gained in ten years of implementation of inverse algorithms based on the parameter estimation theory (OLS, MAP, and Kalman filtering) is summarized and presented. Several examples of estimation of thermophysical properties using transient and pulse techniques are reported and discussed. The thermal conductivity, specific heat capacity, and total hemispherical emissivity of different materials (light insulators, Pyrex, and niobium) are presented and compared with data obtained with consolidated techniques and with literature data.     

Thermophysical Properties of a Quaternary Refrigerant Mixture: Comparison of Dynamic Light Scattering Measurements with a Simple Prediction Method

Dynamic light scattering (DLS) has been used for the measurement of several thermophysical properties of a quaternary refrigerant mixture R-125/143a/32/134a in its liquid phase under saturation conditions. The thermal diffusivity and sound speed have been obtained by light scattering from bulk fluids over a temperature range from about 293 K up to the liquid–vapor critical point. By applying the method of DLS to a liquid–vapor interface, also called surface light scattering (SLS), the saturated liquid kinematic viscosity and surface tension can be determined simultaneously. These properties have been measured from about 243 to 343 K. The results are discussed in comparison with literature data and with a simple prediction method based on the mass-weighted properties of the pure components, expressed as functions of the reduced temperature. Once again, the simple prediction method was shown to be applicable for the calculation of different transport and other thermophysical properties of multicomponent refrigerant mixtures and this with sufficiently high accuracy for technical practice. Moreover, the input data for the simple prediction scheme can be reduced without loss of accuracy by treating binary or ternary mixtures as a subset of the multicomponent mixture.     

Automated System for Calculating Thermophysical Properties of Fluids and Thermal Processes of Cryogenic Plants

An automated system for calculating thermophysical properties of gases and liquids over a wide range of parameters has been developed. On the basis of values of the properties, the processes of isothermal compression, adiabatic throttling, polytropic expansion, heat exchange in two- and multi-stream heat exchangers, separation of vapor-liquid mixtures in the liquid vessel, and rectification in an air separation plant can be analyzed. For a specified structure scheme of a cryogenic plant, optimization of a corresponding thermodynamic cycle can be fulfilled.     

多角度动态光散射法的纳米颗粒精确测量

基于动态光散射原理,采用自主研发的多角度动态光散射装置,对纳米及亚微米颗粒粒径准确测量方法进行了探究。自研装置采用带有光阑组的精密入射光路设计,以及匹配液池及Beam-stop设计,极大提高了信噪比;同时避免了测量角度的互补方向上,由于样品池与空气界面折射率不同导致的反射光信号对有效信号的干扰。在此基础上,对不同浓度、粒径的聚苯乙烯(PS)颗粒溶液进行了测定及不确定度分析。结果表明,对同一粒径的PS颗粒,增加颗粒浓度时,多重散射首先发生于大、小测量角度,越接近90°,发生多重散射的浓度越高;随着粒径增大,受不可忽略的颗粒间相互作用的影响,粒径测量结果表现出了强烈的角度依赖性,甚至波动性。     

一种新的动态光散射纳米颗粒反演算法

由于传统累积量反演算法计算结果随相关时间的变化有较大的波动,提出一种新的累计量算法,此方法直接利用光子相关光谱函数作为目标函数进行反演,减少相关时间选择对测量结果的影响.在介绍传统累积量光子相关光谱法颗粒粒径分布反演算法的基础上,引入以光子相关光谱函数作为累积量算法的目标函数的反演算法,利用实验平台对90 nm的乳胶颗粒进行测量.运用实验获得的相关函数数据研究两种累积量算法和相关时间之间的关系,实验结果表明,采用传统累计量算法其结果受相关时间影响较大,而本文所提算法稳定性好,在较长相关时间范围内基本不受相关时间影响.     

The Imperial College Thermophysical Properties Data Centre

The IUPAC Thermodynamic Tables Project Centre in London has at its disposal considerable expertise on the production and utilization of high-accuracy equations of state which represent the thermodynamic properties of substances. For some years they have been content to propagate this information by the traditional method of book production, but the increasing use of the computer in industry for process design has shown that an additional method was needed. The setting up of the IUPAC Transport Properties Project Centre, also at Imperial College, whose products would also be in demand by industry, afforded the occasion for a new look at the problem. The solution has been to set up the Imperial College Thermophysical Properties Data Centre, which embraces the two IUPAC Project Centres, and for it to establish a link with the existing Physical Properties Data Service of the Institution of Chemical Engineers, thus providing for the dissemination of the available information without involving the Centres in problems such as those of marketing and advertising. This paper outlines the activities of the Centres and discusses the problems in bringing their products to the attention of industry in suitable form.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

多层介质高反射膜的散射特性研究

为了研究多层介质高反射薄膜的散射特性减小光学薄膜的散射损耗,以多层光学薄膜矢量光散射理论为基础,利用光学薄膜的总散射损耗与光学薄膜双向反射分布函数的关系,研究了多层介质高反射薄膜分别在膜层界面粗糙度为完全相关和完全非相关模型下入射角和偏振状态对总散射损耗的影响,以及入射波长对总散射损耗的影响.理论研究结果表明,随着入射角的变化p偏振入射光引起的p偏振的总散射损耗强烈依赖于膜层界面粗糙度的相关特性,尤其是在布儒斯特角附近更为明显;此外,通过对介质高反射膜在两种不同模型下的总散射损耗随入射波长的变化与其反射率谱的比较发现,完全相关模型下的总散射损耗与反射率谱的变化趋势一致,完全非相关模型则恰好反之.     

动态光散射在烟气颗粒粒径分析中的应用

本文阐述了动态光散射测量的基本原理,尝试性地利用动态光散射技术进行了气体中烟气颗粒的粒径测量.利用Brookhaven公司的BI-9000相关器搭建测量平台,探索了动态光散射技术在气体中测量烟气颗粒粒径的方法,分析了在测量中遇到的关键问题,如烟气颗粒浓度.颗粒吸附作用等,并初步提出解决问题的方案.本文先后对两种不同的烟草样本进行实验,两组测量数据表现出明显的差异,同组数据在一定范围内波动,说明了动态光散射在烟气颗粒测量中有一定的应用潜力.     

动态光散射中基于光子计数率的噪声剔除方法

提出一种基于光子计数率的噪声剔除方法消除大颗粒的影响,通过监测每秒的光子计数,若某1s的光子计数明显高于之前5s光子计数的均值,则将这1s的光子计数剔除。分别在20、30、40°散射角度对测量介质为水、标称直径为21.3nm的金颗粒和90nm的标准颗粒进行测试。结果表明:该方法能有效剔除跳变较大的光子计数率,剔除噪声后的有效粒径和分散度都比较稳定,且接近标称值。     

Determination of Surface Tension of Succinonitrile Using a Surface Light Scattering Spectrometer

Liquid/vapor interfacial surface tensions of succinonitrile, NC(CH₂)₂CN, were measured using noninvasive surface light scattering (SLS) spectroscopy. Succinonitrile (SCN) has been and is being used extensively in materials science and fluid physics research, for example, in several theoretical and numerical studies of dendritic growth. It is an established model material with several essential physical properties accurately known with the exception of the liquid/vapor surface tension, _1v, at various temperatures. Using the SLS spectrometer, we have experimentally determined the liquid/vapor surface tension of SCN in the temperature range from just above its melting point (58.1°C) to 118°C using this noninvasive method. Previous measurements of SCN surface tension are extremely limited. To the best of our knowledge, this work is the first to measure the surface tension of succinonitrile noninvasively at melt and elevated temperatures. The SLS spectroscopy is relatively new and unique. This technique has several advantages over classical methods: it is noninvasive, has a good accuracy, and can be used to measure the surface tension and viscosity simultaneously, although the viscosity results are not discussed here. The accuracy of values obtained from this technique on some standard liquids is better than 2% for the surface tension and about 10 to 15% for viscosity. Our measurements gave _1v=42.28–0.0629T±0.2 (mN·m^-1), with T in °C, and the viscosity at 60°C is 2.68±0.3 cp for pure SCN.     

4He Thermophysical Properties: New Ab Initio Calculations

Since 2000, atomic physicists have reduced the uncertainty of the helium-helium “ab initio” potential; for example, from approximately 0.6 % to 0.1 % at 4 bohr, and from 0.8 % to 0.1 % at 5.6 bohr. These results led us to: (1) construct a new inter-atomic potential ϕ₀₇, (2) recalculate values of the second virial coefficient, the viscosity, and the thermal conductivity of ⁴He from 1 K to 10,000 K, and (3), analyze the uncertainties of the thermophysical properties that propagate from the uncertainty of ϕ₀₇ and from the Born-Oppenheimer approximation of the electron-nucleon quantum mechanical system. We correct minor errors in a previous publication [J. J. Hurly and M. R. Moldover, J. Res. Nat. Inst. Standards Technol. 105, 667 (2000)] and compare our results with selected data published after 2000. The ab initio results tabulated here can serve as standards for the measurement of thermophysical properties.     

氢对TC21钛合金热物理性能的影响

目的 获得氢含量对TC21钛合金密度、热扩散系数、比热容和热导率等热物理性能的影响规律.方法 利用固态置氢法对TC21钛合金进行氢处理,利用固体密度测试仪、激光导热仪和差示扫描量热仪等设备测定原始及含有不同氢含量TC21钛合金的热物理性能.结果 随着氢含量的增加,TC21钛合金的密度呈线性降低趋势;TC21钛合金在不同...     

Depth-Resolved Surface Thermophysical Property Measurement by Laser-Produced Plasmas

A new laser-based method for real-time in situ measurement of thermophysical properties of materials has been developed. It entails production by a high-power laser pulse of a plasma plume from the surface of a condensed-phase specimen and simultaneous measurement of a material's response to the excitation. The specimen may be a solid or in a molten state at high temperatures. It has been shown that the thermal diffusivity can be determined, for instance, from the mass loss due to laser excitation. In one implementation the mass loss is determined from the impulse imparted on the surface by the ablated matter which is measured by an impulse transducer. In this paper, we present a new spectroscopic method for measurement of the mass loss, facilitating in situ non-contact measurement of the thermal diffusivity for the first time. An implementation of this method is described, whereby the thermal diffusivity of a complex layered surface is determined as a function of depth with resolutions as small as 13 nm.