Measurements of the viscosity of R134a and R32 in the temperature range 270–340 K at pressures up to 20 MPa

This paper reports new measurements of the liquid viscosity of R134a and R32 in the temperature range 270 to 340 K and pressures up to 20 MPa. The measurements have been carried out in a vibrating-wire instrument calibrated with respect to the standard reference value of the viscosity of water. It is estimated that the uncertainty of the present viscosity data is one of 0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation.     

The viscosity of R32 and R125 at saturation

This paper reports new measurements of the viscosity of R32 and R125, in both the liquid and the vapor phase, over the temperature range 220 to 343 K near the saturation line. The measurements in both liquid and vapor phases have been carried out with a vibrating-wire viscometer calibrated with respect to standard reference values of viscosity. It is estimated that the uncertainty of the present viscosity data is one of 0.5–1%, being limited partly by the accuracy of the available density data. The experimental data have been represented by polynomial functions of temperature for the purposes of interpolation.     

Viscosity Measurements of Ammonia, R32, and R134a. Vapor Buoyancy and Radial Acceleration in Capillary Viscometers

The saturated liquid viscosity of ammonia (NH₃) and of the hydrofluorocarbons, difluoromethane (CH₂F₂, R32) and 1,1,1,2-tetrafluoroethane (CF₃–CH₂F, R134a), was measured in a sealed gravitational viscometer with a straight vertical capillary. The combined temperature range was from 250 to 350 K. The estimated uncertainty of the ammonia measurements is ±3.3 and ±2 to 2.4% for the hydrofluorocarbons with a coverage factor of two. The results are compared with literature data which have been measured with capillary viscometers of different design. Agreement within the combined experimental uncertainty is achieved when some of the literature data sets are corrected for the vapor buoyancy effect and when a revised radial acceleration correction is applied to data which were obtained in viscometers with coiled capillaries. An improved correction for the radial acceleration is proposed. It is necessary to extend inter-national viscometry standards to sealed gravitational capillary instruments because the apparent inconsistencies between refrigerant viscosity data from different laboratories cannot be explained by contaminated samples.     

Thermodynamic properties of R32 + R134a and R125 + R32 mixtures in and beyond the critical region

A parametric crossover equation of state for pure fluids is adapted to binary mixtures. This equation incorporates scaling laws asymptotically close to the critical point and is transformed into a regular classical expansion far away from the critical point. An isomorphic generalization of the law of corresponding states is applied to the prediction of thermodynamic properties and the phase behavior of binary mixtures over a wide region around the locus of vapor-liquid critical points. A comparison is made with experimental data for pure R32, R 125 and R 134a, and for R32 + R 134a and R 125 + R32 binary mixtures. The equation of state yields a good representation of thermodynamic property data in the range of temperatures 0.8T_c(x) ≤ T ≤ 1.5T_c(x) and densities 0.35 ?_c(x) ≤ ? ≤ 1.65?_c(x).     

Transport properties of refrigerants R32, R125, R134a, and R125+R32 mixtures in and beyond the critical regionPropriétés de transport des frigorigènes R32, R125, R134a et des mélanges de R125+R32 dans et au-delà la région critique

A practical representation for the transport coefficients of pure refrigerants R32, R125, R134a, and R125+R32 mixtures is presented which is valid in the vapor–liquid critical region. The crossover expressions for the transport coefficients incorporate scaling laws near the critical point and are transformed to regular background values far away from the critical point. The regular background parts of the transport coefficients of pure refrigerants are obtained from independently fitting pure fluid data. For the calculation of the background contributions of the transport coefficients in binary mixtures, corresponding-states correlations are used. The transport property model is compared with thermal conductivity and thermal diffusivity data for pure refrigerants, and with thermal conductivity data for R125+R32 mixtures. The average relative deviations between the calculated values of the thermal conductivity and experimental data are less than 4–5% at densities ρ0.1ρ_c and temperatures up to T=2T_c.     

The viscosity of liquid R134a

The paper reports new measurements of the viscosity of liquid R134a over the temperature range 235 to 343 K and pressures up to 50 MPa. The measurements have been carried out in a vibrating-wire viscometer calibrated with respect to the viscosity of several liquid hydrocarbons. It is estimated that the uncertainty in the viscosity data reported is ±0.6%. The data therefore have a lower uncertainty than that of earlier measurements of the viscosity of this environmentally acceptable regrigerant. The viscosity data have been represented as a function of density by means of a formulation based upon the rigid, hard-sphere theory of dense fluids with a maximum deviation of ±0.3%. This representation allows the present body of experimental data to be extended to regions of thermodynamic state not covered by the measurements.     

Thermal conductivity of R32 and its mixture with R134a

The liquid thermal conductivity of R32 (CH₂F₂) and R134a (CF₃CH₂F) was measured in the range from 223 to 323 K and from 2 to 20 MPa by the transient hot-wire method. The thermal conductivity of the R32+R134a mixture was also measured in the same range by varying the mass fraction of R32. The measured data are analyzed to obtain a correlation in terms of temperature, pressure and composition of the mixture. The uncertainty of our measurements is estimated to be within ±2%.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Thermal conductivity of R32 and R125 in the liquid phase at the saturation vapor pressure

The first measurements of the thermal conductivity of two refrigerants which are candidates for the replacement of those fluids currently in use are reported. Specifically, results are given for the thermal conductivity of R32 and R125 in the liquid phase along the saturation line. The measurements, which have been made by the transient hot-wire technique, extend over the temperature range from 205 to 303 K for R32 and from 225 to 306 K for R125; the results have an estimated uncertainty of ±1.0%.     

The Thermal Diffusivity of the Refrigerants R32, R125, and R143a

The thermal diffusivity of the halogenated fluorocarbons R32, R125, and R143a was systematically measured in a wide region of state around the liquid-vapor critical point using dynamic light scattering as the measuring method. The experimental setup is capable of measuring in homodyne (high light intensity) or heterodyne mode (low light intensity). Especially in the vicinity of the critical point, this method is superior to other techniques since no calibration is necessary and the fluid is held in thermodynamic equilibrium. With high light-scattering intensities in the near-critical region, the uncertainty of the measurements is about 0.5% and increases to up to 5% far from the critical point. Measurements were performed in both coexisting phases, along the critical isochore, and along seven isotherms. The range of application is characterized in terms of the reduced density and pressure by 0.3 < / _c < 2 and 0.5 < p/p _c < 2.5. These limits are defined by low scattering intensities and by the mechanical limits of the apparatus due to high pressures of the fluid. The corresponding temperature range is from 300 to 390 K. When approaching the critical point, the thermal diffusivity drops by orders of magnitude and can be expressed by simple scaling laws depending on the reduced temperature difference = (T–T _c )/T _c . In addition to the thermal diffusivity, the refractive index and the critical parameters T _c , p _c are measured and presented. The density of the fluid is calculated from the refractive index using the Lorentz–Lorenz relation.     

R32/R134a和R407C用于变浓度热泵系统的实验

为了解决R32/R134a应用于变浓度热泵系统存在的排气温度过高问题,提出使用三元混合工质R407C用于该系统中.以R32/R134a和R407C作为工质在变浓度容量调节热泵系统中进行了吸气压力不变时的变浓度实验.实验结果表明,R407C在本系统中变浓度范围低于R32/R134a,但R407C的排气温度和耗功均低于R32/R134a,具有良好的变浓度调节潜力.     

Critical parameters for HFC134a, HFC32 and HFC125

The vapour-liquid coexistence curves near the critical point for HFC134a (CF₃CH₂F: 1,1,1,2-tetrafluoroethane), HFC32 (CH₂F₂: difluoromethane) and HFC125 (CHF₂CF₃: pentafluoroethane) have been measured by visual observation of the meniscus disappearance. Three sets of 17 experimental results for the saturated liquid or vapour densities for HFC134a, HFC32 and HFC125 have been obtained in the reduced temperature range T/T_c > 0.96 and in the reduced density range 0.4 < ρ/ρ_c < 1.7. From these measurements, the critical temperature and the critical density for these HFCs have been determined in consideration of the meniscus disappearance level as well as the intensity of the critical opalescence. The critical pressure has been calculated by the extrapolation of the vapour-pressure correlation. The uncertainties of the critical temperature, critical density and critical pressure are estimated to be within ± 10 mK, ± 5 kg m⁻³ and ± 9 kPa, respectively.     

Measurements of the viscosity of refrigerants in the vapor phase

Measurements of the viscosity of refrigerants R124, R125, R134a, and R152a in the vapor phase are presented. The measurements, performed in a new vibrating-wire instrument, cover a temperature range from 273 to 333 K from about atmospheric pressure up to below the saturation pressure. The uncertainty of the reported values is estimated to be better than ±1%. Comparison with measurements of other investigators reveals a lack of reliable data in the vapor region for these compounds. Paper presented at the Fourth Asian Thermophysical Properties Conference., September 5–8, 1995, Tokyo, Japan.     

Liquid Thermal Conductivity of Ternary Mixtures of Difluoromethane (R32), Pentafluoroethane (R125), and 1,1,1,2-Tetrafluoroethane (R134a)1

The thermal conductivities of ternary refrigerant mixtures of difluoromethane (R32), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) in the liquid phase have been measured by the transient hot-wire method with one bare platinum wire. The experiments were performed in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa at various compositions. The measured data are correlated as a function of temperature, pressure, and composition. From the correlation, we can calculate the thermal conductivity of pure refrigerants and their binary or ternary refrigerant mixtures. The uncertainty of the measurements is estimated to be ±2%.     

Liquid Thermal Conductivity of Binary Mixtures of Pentafluoroethane (R125) and 1,1,1,2-Tetrafluoroethane (R134a)

Thermal conductivities of zeotropic mixtures of R125 (CF₃CHF₂) and R134a (CF₃CH₂F) in the liquid phase are reported. Thermal conductivities have been measured by a transient hot-wire method with one bare platinum wire. Measurements have been carried out in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa. The dependence of thermal conductivity on temperature, pressure, and composition of the binary mixture is presented. Measured thermal conductivity data are correlated as a function of temperature, pressure, and overall composition of the mixture. The uncertainty of our measurements was estimated to be better than 2%.     

R32和R32/R1234yf混合工质黏度实验测量及模型

本文针对含HFOs类混合制冷剂黏度开展实验和模型研究。采用振动弦法黏度计对R32纯质和R32/R1234yf混合制冷剂黏度进行了实验测量,测量的温度范围分别为263~350 K、263~360 K,压力最高均为30 MPa,实验系统黏度测量的不确定度为2%。本文共获得了177组实验数据,利用得到的实验数据,基于硬球模型分别拟合了R32纯质和R32/R1234yf混合制冷剂黏度方程。R32纯质黏度实验数据与方程的平均绝对偏差为0.28%,最大绝对偏差为0.92%;R32/R1234yf混合工质黏度实验数据与方程的平均绝对偏差为0.69%,最大绝对偏差为2.09%。由此可见,实验数据和黏度模型吻合较好,为R32和R32/R1234yf混合制冷剂的应用研究提供了重要参考依据。     

Thermal conductivity of refrigerants R123, R134a,and R125 at low temperatures

Using a transient coaxial cylinder technique, thermal conductivities were measured for liquid 1,1,1-trifluoro-2,2-dichloroethane (refrigerant R123), 1,1,1,2-tetrafluoroethane (refrigerant R134a). and pentalluoroethane (refrigerant R 125). The uncertainty of the experimental data is estimated to be within 2–3 %. Thermal conductivities of refrigerants were measured at temperatures ranging from –114 to 20°C under pressures up to IOMPa. The apparatus was calibrated with four kinds of liquids and gases. The features of the density dependence of thermal conductivity are indicated. Existing equations for calculating the coefficient are analyzed in cases where development has been sufficient to enable comparisons to be made with experiment. Saturated-liquid thermal conductivities for R134a and R123 are compared with corresponding experimental values.     

Measurements of the viscosity of liquid R22, R124, and R125 in the temperature range 273–333 K at pressures up to 17 MPa

Viscosity masurements of refrigerants R22, R124, and R125 in the liquid phase have been performed in the temperature range 273–333 K and at pressures up to about 17 MPa. A vibrating-wire instrument has been employed. The overall uncertainty of the experimental values is estimated to be ±0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation.     

Vapor–Liquid Equilibrium of HFC-32/134a And HFC-125/134a Systems

A vapor-liquid equilibrium apparatus has been developed and used to obtain data for the binary HFC-32/134a and HFC-125/134a systems. Twenty-two equilibrium data are obtained for the HFC-32/134a system over the temperature range from 258.15 to 283.15 K at 5 K intervals and the composition range from 0.2 to 0.8 liquid mole fraction. Twenty-five equilibrium data are obtained for the HFC-125/134a system over the temperature range from 263.15 to 303.15 K at 10 K intervals and the composition range from 0.18 to 0.81 liquid mole friction. These data have been tested and found to be thermodynamically consistent. Based upon the present data, the binary interaction parameters of the Carnahan-Starling-De Santis (CSD) and Redlich–Kwong–Soave (RKS) equations of state are calculated for five isotherms for the HFC-125/134a mixture and six isotherms for the HFC-32/134a mixture. The calculated results from the CSD equation are compared with data in the open literature.     

Isochoric Heat Capacity Measurements for Binary Refrigerant Mixtures Containing Difluoromethane (R32), Pentafluoroethane (R125), 1,1,1,2-Tetrafluoroethane (R134a), and Trifluoroethane (R143a) from 200 to 345 K at Pressures to 35 MPa

Molar heat capacities at constant volume C _v were measured for binary refrigerant mixtures with an adiabatic calorimeter with gravimetric determinations of the amount of substance. Temperatures ranged from 200 to 345 K, while pressures extended up to 35 MPa. Measurements were conducted on liquid samples with equimolar compositions for the following binary systems: R32/R134a, R32/R125, R125/R134a, and R125/R143a. The uncertainty is 0.002 K for the temperature rise and is 0.2% for the change-of-volume work, which is the principal source of uncertainty. The expanded relative uncertainty (with a coverage factor k=2 and thus a two-standard deviation estimate) for C _v is estimated to be 0.7%.     

Composition shift in liquid-recirculation refrigerating systems: an experimental investigation for the pure fluid R134a and the mixture R32/134aChangement de composition dans les systèmes frigorifiques à recirculation de liquide : étude expérimentale du frigorigène pur R134a et d'un mélange de R32+R134a

The ability of zeotropic mixtures with a remarkable temperature glide to operate in liquid-recirculation systems is investigated and the results of an experimental comparison between the performances of the pure fluid R134a and the zeotropic mixture R32/134a (25/75% by mass) are presented. R134a performs slightly better in the liquid-recirculation mode than in the traditional dry-expansion mode; on the other hand, liquid-recirculation configuration has a detrimental effect on the zeotropic mixture's performance. The reason for this detrimental effect is the mixture component separation which occurs at the liquid/vapor separator. The effect of this separation is investigated using gas chromatograph analysis.