载冷剂低温热物性测试方法综述

航天器内的温度通过热控制系统中载冷剂的强制对流换热来调节。在研制和选择载冷剂时,根据载冷剂的性能要求,需要对流体工质在低温下的热物性参数进行测量。对现有的载冷剂物性测试方法进行了综述,总结了测量载冷剂密度、凝固点、沸点、黏度等参数的方法,并通过比较得出绝热量热法是低温下测量液体比热容的最佳方法,径向热流法适合于低温下测量液体工质的导热系数。     

General study of the thermophysical properties of alkaline earth metals

Several experimental devices are used to measure the density, surface tension, viscosity, and heat capacity of barium, calcium, and cesium from their melting points to 1800°K. Measurement methods are described and results presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 6, pp. 972–979, December, 1980.     

Viscosity and density of CuO nanolubricant

This paper presents liquid kinematic viscosity and density measurements of a synthetic polyolester based copper (II) oxide (CuO) nanoparticle dispersion (nanolubricant) at atmospheric pressure for a temperature range from approximately 288 K to 318 K. The polyolester was a commercially available chiller lubricant. The CuO particles were approximately 30 nm diameter, spherical, and well dispersed in the lubricant. Viscosity and density measurements were made for the pure base lubricant along with three nanolubricants with differing nanoparticle mass fractions (2.9%, 5.6% and 39.2%). The viscosity and the density were shown to increase with respect to increasing nanoparticle mass fraction. Correlations of the viscosity and the density are presented as a function of temperature and nanoparticle concentration. The measurements are important for the design of nanolubricants for heat transfer and flow applications.     

Prediction of transport properties of R22-DMF refrigerant-absorbent combinations

The present work aims to evaluate the transport properties of R22-DMF solutions; one of the most promising combinations for absorption refrigeration. A number of methods have been used to estimate the thermal conductivity, viscosity and surface tension. The selection of suitable methods has been made by computing the properties of ammonia-water mixtures and comparing them with available experimental data. Other thermophysical properties, i.e. thermal diffusivity, specific heat and liquid density, have been predicted using standard, well established methods over a wide range of temperature and composition. Correlations have been developed to express each property as a function of composition and temperature. The properties are also presented in a suitable graphical form.     

Characterization and stability analysis of oil‐based copper oxide nanofluids for medium temperature solar collectors

Thermal oils are widely used as heat transfer fluids in medium temperature applications. Addition of small amounts of nanoparticles in such fluids can significantly improve their thermophysical properties. This paper presents experimental investigation of an oil‐based nanofluids prepared by dispersing different concentrations (0.25 wt%–1.0 wt%) of copper oxide nanoparticles in Therminol‐55 oil using two‐step method. Shear mixing and ultrasonication were used for uniform distribution and de‐agglomeration of nanoparticles to enhance the stability of the suspensions. The effect of nanoparticles concentrations on thermophysical properties of the nanofluids was analysed by measuring thermal conductivity, dynamic viscosity, effective density and specific heat capacity at different temperatures (25 °C–130 °C). Thermal conductivity exhibited increasing trend with rising temperature and increase in nanoparticles loading. A significant decrease in dynamic viscosity and effective density against increasing temperature makes it suitable for medium temperature applications. Nano‐oils with improved thermal properties are expected to increase the efficiency of concentrating solar thermal collectors.     

Thermophysical Properties of γ-Titanium Aluminide: The European IMPRESS Project

In the framework of its 6th Framework Programme, the European Union funds the Integrated Project IMPRESS, related to industrial applications of Ti–Al and Ni–Al alloys. One central task of this project is the precise determination of the relevant thermophysical properties of selected alloys for both the solid and liquid phases. The properties to be measured include thermal data such as heat of fusion, specific heat, and thermal conductivity, as well as thermophysical and transport properties such as density, surface tension, and viscosity. In addition to conventional high-temperature equipment, containerless methods are used. This article introduces the IMPRESS project, and discusses the first results obtained to date.     

On the fluid thermal activity coefficient using water as an example

In conformity with the experimental results on the density, heat conductivity, specific heat, and viscosity of water, it is established that 1) the fluid thermal activity coefficient can be expressed in a form analogous to the equation of state, and 2) a linear dependence exists between the fluid thermal activity and heat conductivity coefficients as well as the viscosity.

     

A Vibrating Plate Fabricated by the Methods of Microelectromechanical Systems (MEMS) for the Simultaneous Measurement of Density and Viscosity: Results for Argon at Temperatures Between 323 and 423K at Pressures up to 68 MPa

In the petroleum industry, measurements of the density and viscosity of petroleum reservoir fluids are required to determine the value of the produced fluid and the production strategy. Measurements of the density and viscosity of petroleum fluids require a transducer that can operate at reservoir conditions, and results with an uncertainty of about ±1% in density and ±10% in viscosity are needed to guide value and exploitation calculations with sufficient rigor. Necessarily, these specifications place robustness as a superior priority to accuracy for the design. A vibrating plate, with dimensions of the order of 1 mm and a mass of about 0.12 mg, clamped along one edge, has been fabricated, with the methods of Microelectromechanical (MEMS) technology, to provide measurements of both density and viscosity of fluids in which it is immersed. The resonance frequency (at pressure p = 0 is about 12 kHz) and quality factor (at p = 0 is about 2800) of the first order bending (flexural) mode of the plate are combined with semi-empirical working equations, coefficients obtained by calibration, and the mechanical properties of the plate to provide the density and viscosity of the fluid into which it is immersed. When the device was surrounded by argon at temperatures between 348 and 423 K and at pressures between 20 and 68 MPa, the density and viscosity were determined with an expanded (k = 2) uncertainty, including the calibration, of about ±0.35% and ±3%, respectively. These results, when compared with accepted correlations for argon reported in the literature, were found to lie within ±0.8% for density and less than ±5% for viscosity of literature values, which are within a reasonable multiple of the relative combined expanded (k = 2) uncertainty.     

Thermodynamic properties for the quaternary system H2O + CH3OH + LiBr + ZnCl2

The thermodynamic properties (solubility, vapour pressure, density, viscosity, heat capacity and heat of mixing) of the H₂O + CH₃OH + LiBr + ZnCl₂ (9:1 H₂O:CH₃OH and 1:1 LiBr:ZnCl₂ by mass) system using H₂O + CH₃OH as the working media and LiBr + ZnCl₂ as the absorbents were measured. The solubility data were obtained in the temperature range from 270.35 to 389.55 K. The measurements of vapour pressure, density, viscosity and heat capacity were carried out at various temperatures and absorbent concentrations. The differential heat of dilution and differential heat of solution at 298.15 K were measured for solutionw with absorbent concentrations from 0 to 75.2 wt%. The integral heat of mixing data at 298.15 K were obtained from both sets of experimental data. The integral heats of mixing for this quaternary system showed exothermic behaviour. The vapour pressure data were correlated with an Antoine-type equation. An empirical formula for the heat capacity was obtained from experimental data. The experimental data for the basic thermodynamic properties of this quaternary system were compared with those of the basic H₂O + LiBr system.     

Flow and heat transfer of a micropolar fluid in an axisymmetric stagnation flow on a cylinder with variable properties and suction (numerical study)

Summary. In this paper, an analysis is presented to study the effects of variable properties, density, viscosity and thermal conductivity of a micropolar fluid flow and heat transfer in an axisymmetric stagnation flow on a horizontal cylinder with suction, numerically. The fluid density and the thermal conductivity are assumed to vary linearly with temperature. However, the fluid viscosity is assumed to vary as a reciprocal of a linear function of temperature. The similarity solution is used to transform the problem under consideration into a boundary value problem of nonlinear coupled ordinary differential equations which are solved numerically by using the Chebyshev finite difference method (ChFD). Numerical results are carried out for various values of the dimensionless parameters of the problem. The numerical results show variable density, variable viscosity, variable thermal conductivity and micropolar parameters, which have significant influences on the azimuthal and the angular velocities and temperature profiles, shear stress, couple stress and the Nusselt number. The numerical results have demonstrated that with increasing temperature ratio parameter the azimuthal velocity decreases. With increasing variable viscosity parameter the temperature increases, whereas the azimuthal and the angular velocities decrease. Also, the azimuthal and the angular velocities increase and the temperature decreases as the variable conductivity parameter increases. Finally, the pressure increases as the suction parameter increases.     

Thermophysical properties of aqueous NaOH−H2O solutions at high concentrations

The working fluids, used in the majority of all mechanical heat pumps, are expected to be phased out within some few years due to their contribution to the stratospheric ozone depletion and global warming. Absorption heat pumps and transformers are receiving a new renaissance in the field of heating, refrigeration, air-conditioning, and heat recovery. Sodium hydroxide solutions are more propitious to the pulp and paper industry compared to other working pairs. Novel correlations have been developed to compute the vapor pressure, density, enthalpy, and viscosity of sodium hydroxide solutions. These correlations cover the most extensive range of validity ever proposed: 273–473 K for temperatures and 0.2–1 kg water per kg solution for concentrations.     

Study of viscosity and specific heat capacity characteristics of water-based Al2O3 nanofluids at low particle concentrations

In this paper, the specific heat capacity and viscosity properties of water-based nanofluids containing alumina nanoparticles of 47 nm average particle diameter at low concentrations are studied. Nanofluids were prepared with deionised water as base fluid at room temperature by adding nanoparticles at low volume concentration in the range of 0.01%–1% to measure viscosity. The effect of temperature on viscosity of the nanofluid was determined based on the experiments conducted in the temperature range of 25°C to 45°C. The results indicate a nonlinear increase of viscosity with particle concentration due to aggregation of particles. The estimated specific heat capacity of the nanofluid decreased with increase of particle concentration due to increase in thermal diffusivity. Generalised regression equations for estimating the viscosity and specific heat capacity of nanofluids for a particular range of particle concentration, particle diameter and temperature are established.     

Cubic spline fits to thermodynamic and transport parameters of liquid 4He above the λ transition

A survey has been made of the more recent experimental measurements of the viscosity, density, thermal expansion coefficient, thermal conductivity, and specific heat of liquid ⁴He from the region up to 4.2 K. Cubic spline fits to these data are provided using a mean squares approach. The fits are used to plot the temperature dependence of the kinematic viscosity, the thermal diffusivity, and the Prandtl number.Research supported by NSF grant CME 80-07478.     

Special features of heat transfer under conditions of heat protection of high-temperature firing walls of components of modern power-generating units by way of tangential injection

In order to more precisely define the characteristics of heat transfer under conditions of protection of firing wall by means of tangential injection in the case of its high temperature (in particular, higher-thanadiabatic temperature) and to assess the effect of degree of turbulence of the incoming gas flow on heat transfer, a numerical investigation is performed under conditions of parameters typical of combustors of gas-turbine plants (GTP) with high parameters of the working medium. In so doing, the heat flux distribution, the profiles of turbulence intensity, the distribution of turbulent viscosity in the injection zone region under study, and other characteristics are determined. The low-Reynolds k-ε model with wall functions and a new model of turbulent viscosity without wall functions are employed. It is found that a maximum of turbulent viscosity takes place behind the exit section of the injection slit with a shift to the main flow under conditions of tangential injection on an isothermal surface with a temperature much in excess of injection temperature (in a more general case, T _w > T _ad). This causes impairment of heat protection by injection, i.e., an increase in heat fluxes in the computational domain compared to heat fluxes calculated using integral methods.     

Experimental investigation on thermophysical properties of solar glycol dispersed with multi-walled carbon nanotubes

This article deals with well-dispersed solar glycol-based nanofluids containing multi-walled carbon nanotube (MWCNT) nanoparticles with different particle volume concentrations of 0.1%, 0.2%, 0.3%, and 0.4% prepared by typical two-step method. Thermal conductivity, viscosity and specific heat capacity of solar glycol (SG)-based MWCNT nanofluids, in the temperature range of 30°C–70°C were measured. The values of density showed a noticeable deviation from the predictions of Pak and Cho correlation. Hence, correlations are developed for thermal conductivity and viscosity from the experimental results obtained from the various range parameters of interest. The presence of MWCNT enhanced the thermal conductivity of the nanofluids by 17.26% at 0.4 vol.% particle concentration at 70°C. The relative viscosity of MWCNT nanofluids depends on the nanoparticles percentage concentration and decreases significantly with increase in temperature for higher concentrations. The presence of MWCNT enhances the specific heat of the nanofluids significantly, and this enrichment decreases with the increase of the MWCNT concentration. MWCNT/SG represents a new and innovative class of heat-transfer fluid, which possesses excellent thermophysical properties. The MWCNT/SG-based nanofluids could be suitable working fluids for solar thermal and automobile applications.     

Viscosity and density of binary mixtures of cyclohexane with n-octane,n-dodecane,and n-hexadecane under high pressures

The viscosity and density of three binary mixtures of cyclohexane with n-octane, n-dodecane, and n-hexadecane have been measured at 298, 323, and 348 K at pressures up to 150 MPa or freezing pressures. The measurements of the viscosity were performed by a torsionally vibrating crystal viscometer on a relative basis using benzene and cyclohexane as reference materials. The density was measured using a high-pressure burette apparatus. The uncertainties of the measurements are estimated to be less than 2% for viscosity and 0.1% for density, respectively. The effects of temperature, pressure, density, and composition on the viscosity are discussed. Applicabilities of several empirical correlating equations to the viscosity data were examined.     

超临界流体在纳米材料制备中的应用

超临界流体具有粘度低,密度大,较好的流动、传质、传热和溶解性等特性。超临界流体对状态参数的改变十分敏感,温度和压力较小的变化就会使流体的性质发生较大的改变。超临界流体可作为热敏性物质分离纯化方法及产品分析和测定手段,本文主要介绍超临界流体在纳米材料制备中的应用。     

Flow and convection heat transfer characteristics of CO2 mixed with lubricating oil at super-critical pressures in small tube during cooling

This paper describes the heat transfer and the pressure drop characteristics of CO₂ mixed with small amounts of compatible lubricating oil at super-critical pressures inside horizontal tubes with inner diameters of 1.98 mm and 4.14 mm during cooling. The heat transfer coefficients and pressure drops were measured. The results show that for the oil-free cases, the correlation proposed by Dang and Hihara accurately predicted the heat transfer coefficients and Petukhov’s correlation was found to predict the frictional pressure drops reasonably. Entrainment of the lubricating oil reduced the heat transfer coefficients and increased the pressure drops. Analysis showed that the heat transfer coefficients of the CO₂/oil mixture are strongly related to the density and viscosity ratios of the oil to the CO₂. An empirical correlation was developed based on the measured data, which predicts most of the experimental data within a deviation of 20%.     

He I-He II coexistence near the superfluid transition

We have made a numerical scheme of solving two fluid hydrodynamics near the point, which includes the mass density, momentum density, entropy density, and complex order parameter. In our model the normal fluid velocity vanishes at the boundaries due to finite viscosity. As preliminary examples we examine coexistence of a superfluid region and a normal fluid region in two space dimensions firstly in heat flow and secondly in gravity and heat flow. We observe formation of a vortex from a wall in the second case.     

A Comparison of Surface Tension,Viscosity, and Density of Sn and Sn–Ag Alloys Using Different Measurement Techniques

This work is aimed at comparing several methods for the measurement of physical properties for molten Sn and Sn–Ag alloys, namely, surface tension, density, and viscosity. The method used for viscosity in this work is the modified capillary method. For surface tension and density, the data used for comparison were previously measured using the maximum bubble pressure method and the dilatometer technique, respectively, for four Sn–Ag alloys having (3.8, 32, 55, and 68) at% Ag. The results are compared with those obtained using a new method based on a fluid draining from a crucible under the influence of gravity, designated the Roach–Henein (RH) method. This new method enables the determination of these three physical properties in one set of measurements. Liquid Sn was used as well as two liquid Sn–Ag alloys having (3.8 and 34.6) at% Ag with the RH method. It was determined that the RH method may be used to simultaneously obtain surface tension, viscosity, and density and that the errors associated with these measurements were similar to those obtained using traditional and separate techniques. Comparisons of the measured viscosity and surface tension to those predicted using thermodynamic models will also be presented. Finally a comparison of mixing model predictions with the experimentally measured alloy surface tension and viscosity is also presented.