Viscosity of Alternative Refrigerants R407C and R407E in the Vapor Phase from 298.15 to 423.15 K

This paper presents new measurements of the viscosity of gaseous R407C (23 mass% HFC-32, 25 mass% HFC-125, 52 mass% HFC-143a) and R407E (25 mass% HFC-32, 15 mass% HFC-125, 60 mass% HFC-143a). The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K. The densities of these two fluid mixtures were calculated with the equation-of-state model in REFPROP. The viscosity at normal pressures was analyzed with the extended law of corresponding states developed by Kestin et al., and the scaling parameters needed in the analysis were obtained from our previous studies for the viscosity of the binary mixtures consisting of HFC-32, HFC-125, and HFC-134a. The modified Enskog theory developed by Vesovic and Wakeham (V-W method) was applied to predict the viscosity for the ternary gaseous HFC mixtures under pressure. As for the calculation of pseudo-radial distribution functions in mixtures, a method based on the equation of state for hard-sphere fluid mixtures proposed by Carnahan-Starling was applied. It was found that the V-W method can predict the viscosity of R407C and R407E without any additional parameters for the ternary mixture.     

Formation Conditions of Clathrates Between HFC Alternative Refrigerants and Water

There are two promising candidates as alternative refrigerants for air-conditioners and heat pumps. The first is R407C, which is composed of HFC-32 (23 mass%), HFC-125 (25 mass%), and HFC-134a (52 mass%). The second is R410A, which is composed of HFC-32 (50 mass%) and HFC-125 (50 mass%). In this study, formation conditions of clathrate compounds between water and HFC alternative refrigerants such as HFC-32, HFC-125, HFC-134a, and their mixtures, R407C and R410A, were investigated. Phase diagrams of clathrates of these HFC alternative refrigerants and their mixtures were determined. From the phase diagrams, the critical decomposition temperature and the critical decomposition pressure were determined. The relationship between the critical decomposition points for the clathrates of HFC-32, HFC-125, HFC-134a, R410A, and R407C were studied. It is found that R407C and R410A form clathrate compounds with water under the evaporating temperature condition in the refrigeration cycle of air-conditioners and heat pumps.     

Viscosity of Gaseous Mixtures of HFC-125+HFC-32

This paper reports experimental results for the viscosity of gaseous mixtures of HFC-125 (pentafluoroethane)+HFC-32 (difluoromethane). The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15K. The viscosity was measured for three mixtures (mole fraction of HFC-125 is 0.7498, 0.4998, or 0.2475). The viscosity at normal pressure was analyzed with the extended law of corresponding states developed by Kestin et al. and the scaling parameters were obtained for unlike-pair interactions between HFC-125 and HFC-32. The modified Enskog theory developed by Vesovic and Wakeham was applied to predict the viscosity for the binary gaseous mixtures under pressure. For the calculation of the pseudo-radial distribution function in mixtures, a method based on the Carnahan–Starling equation for the radial distribution function of hard sphere mixtures is proposed.     

用于冷冻冷藏制冷系统的新型制冷剂的理论研究

综述在冷冻冷藏系统中制冷剂替代研究的现状。在此基础上,提出一种新的混合制冷剂（HFC-161/HFC-125/HFC-143a,15/45/40）用于替代HFC-404A,该新型制冷剂的ODP为零,GWP比HFC-404A和R507A要小,其基本热力学性能与HFC-404A相近。对新型混合制冷剂和HFC-404A的循环性能进行理论分析与比较。结果表明,新型混合制冷剂的性能要比HFC-404A优越,环境性能更好,是HFC-404A潜有力的替代制冷剂。     

Viscosity of Gaseous Mixtures of HFC-134a (1,1,1,2-Tetrafluoroethane)+HFC-32 (Difluoromethane)

This paper reports experimental results for the viscosity of gaseous mixtures of HFC-134a (1,1,1,2-tetrafluoroethane)+HFC-32 (difluoromethane). The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K. The viscosity was measured for three mixtures containing 25.00, 52.40, and 74.98 mole% HFC-134a in HFC-32. Experimental results for the viscosity at normal pressures show a minimum as plotted against mole fraction in the higher temperature region, which may be the first experimental observation of the minima for dilute binary gaseous mixtures of HFCs. The viscosity at normal pressures was analyzed with the extended law of corresponding states developed by Kestin et al., and the scaling parameters were obtained for unlike-pair interactions between HFC-32 and HFC-134a. The modified Enskog theory developed by Vesovic and Wakeham was applied to predict the viscosity for the binary gaseous mixtures under pressure. As for the calculation of pseudo-radial distribution functions in mixtures, a method based on the equation of state for hard-sphere fluid mixtures proposed by Carnahan–Starling was applied.     

Effect of dissolved lubricating oils on the viscosity of alternative refrigerants

The operation of refrigeration systems involves the circulation of a working fluid which is actually a mixture of refrigerant and lubricant oil. Since the viscosity of oil and that of refrigerants normally differ by up to a factor of 4, the effect of dissolved oil is very large. In order to use new alternative refrigerants, accurate information on thermophysical properties of refrigerant-oil mixtures is needed. In the present study, the viscosity of refrigerant-oil mixtures was measured for HCFC-123 + 3GSD and HFC-134a + PAG in the compressed liquid region with a falling-ball viscometer. The temperature range of the measurements was 253–333 K.     

Viscosity of Gaseous Mixtures of HFC-125 + Propane from 298.15 to 423.15 K at Pressures to 6.7 MPa

This paper reports experimental results for the viscosity of gaseous mixtures of HFC-125 (pentafluoroethane) + propane. The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K. The viscosity was measured for two mixtures containing 50.11 and 75.03 mol% HFC-125 in propane. The viscosity at normal pressure was analyzed with the extended law of corresponding states developed by Kestin et al., and the scaling parameters were obtained for unlike-pair interactions between HFC-125 and propane. The modified Enskog theory developed by Vesovic and Wakeham was applied to predict the viscosity for the binary gaseous mixtures under pressure. From comparisons between experimental results and calculated values of the HFC-125 + propane system, it should be concluded that the Vesovic-Wakeham method gives reliable predictions for the viscosity of a gaseous mixture containing both polar and nonpolar compounds.     

Thermal Conductivity of Binary Refrigerant Mixtures of HFC-32/125 and HFC-32/134a in the Liquid Phase

The liquid thermal conductivity of mixtures of HFC-32/125 and HFC-32/134a was measured using the transient hot-wire apparatus in the temperature ranges from 213 to 293 K and from 193 to 313 K, respectively, in the pressure range from 2 to 30 MPa and with HFC-32 mass fractions of 0.249, 0.500, and 0.750 for each system. The uncertainty of the thermal conductivity was estimated to be ±0.7%. For practical applications, the thermal conductivity data for the two mixtures were represented by a polynomial in temperature, pressure, and mass fraction of HFC-32 with a standard deviation of 1.0%.     

Gaseous thermal conductivity of difluoromethane (HFC-32), pentafluoroethane (HFC-125), and their mixtures

The gaseous thermal conductivity of dilluoromethane (HFC-32). pentalluoroethane (HFC-125). and their binary mixtures was measured with a transient hot-wire apparatus in the temperature ranges 283–333 K at pressures up to saturation. The uncertainty of the data is estimated to be within I %. The thermal conductivity as a function of composition of the mixtures at constant pressure and temperature is found to have a small maximum near 0.3–0.4 mole fraction of HFC-32. The gaseous thermal-conductivity data obtained for pure HFC-32 and HFC-125 were correlated with temperature and density together with the liquid thermal-conductivity data from the literature, based on the excess thermal-conductivity concept. The composition dependence of the thermal conductivity at a constant temperature is represented with the aid of the Wassiljewa equation.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado. U.S.A.     

Thermal Conductivity of HFC-32, HFC-125, and HFC-134a in the Solid Phase

Measurements of the thermal conductivity of HFC-32, HFC-125, and HFC-134a were carried out for the first time in both solid and liquid phases at the saturation pressure at room temperature and in the temperature ranges from 120 to 263, from 140 to 213, and from 130 to 295 K, respectively. A transient hot-wire instrument using one bare platinum wire was employed for measurements, with an uncertainty of less than ±2%. The experimental results demonstrated that the thermal conductivity of HFC-32, HFC-125, and HFC-134a in the solid phase showed a positive temperature dependence. For HFC-32 and HFC-125, there were big jumps between the solid and the liquid thermal conductivity at the melting point. But for HFC-134a, the solid and liquid thermal conductivity at the melting point is almost-continuous.     

制冷工质HFC-134a热力学性质计算模型

根据国外有关资料,对比分析了HFC-134a两组基于MH方程的热力学性质参数方程,优化组合出较为精确的HFC-134a热力学性质计算模型,推导了相应的焓熵计算公式,用Visual Fortran 5.0编程计算了所得模型的部分焓熵值,验证了该模型的准确性,在常见的制冷空调工程实用工作温度和压力范围内有良好的计算精度,全部计算公式均适用于工程设计应用.     

Thermal conductivity of alternative refrigerants in the liquid phase

Measurements ofthe thermal conductivity of five alternative refrigerants. namely, difluoromethane HFC-321. pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichloropentafluoropropanes (HCFC-225ca and HCFC-225cb). are carried out in the liquid phase, The range of temperature is 253–324 K for HFC-32, 257–305 K for HFC-125, 268–314 K for HFC-134a. 267–325 K for HCFC-225ca, and 286–345 K for HCFC-225cb, The pressure rank is from saturation to 30 MPa, The reproducibility of the data is better than 0.5% and the accuracy of the data is estimated to be of the order of 1%. The experimental results for the thermal conductivity ofeach substance are correlated by an equation which is a function of temperature and pressure. A short discussion is given to the comparison of the present results with literature values for HFC-125, The saturated liquid thermal conductivity values of HFC-32. HFC-125, and HFC-143a are compared with those of chlorodifluoromethane (HCFC-22) and tetrafluoroethane (HFC-134a) and it is shown that the value of HFC-32 is highest, while that of HFC-125 is lowest, among these substances, The dependence of thermal conductivity on number of fluorine atoms among the refrigerants with the same number of carbon and hydrogen atoms is discussed.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado. U.S.A.     

Condensation heat transfer coefficients of halogenated binary refrigerant mixtures on a smooth tube

In this study, external condensation heat transfer coefficients (HTCs) of nonazeotropic refrigerant mixtures of HFC32/HFC134a and HFC134a/HCFC123 at various compositions were measured on a horizontal smooth tube of a 19 mm outside diameter. All data were taken at the vapor temperature of 39 °C with a wall subcooling of 3–8 °C. Test results showed that HTCs of the tested mixtures were 19.4–85.1% lower than the ideal values calculated by the mole fraction weighting of the HTCs of the pure components. A thermal resistance due to the diffusion vapor film seemed to be partly responsible for the significant reduction of HTCs with these nonazeotropic mixtures.     

Viscosities of HFC-32 and HFC-32/lubricant mixtures

A modified capillary tube method has been used to measure viscosities for HFC32 over a temperature range from -20 to 90°C and a pressure range from 0.1 to 5.3 M Pa, and for the liquid mixtures of HFC-32 with a synthetic polyolester oil at temperatures from 20 to 75°C and oil mass fractions from 0.44 to 1. Estimated uncertainties in the measured viscosities do not exceed ± 1.2 and ± 1.8°% for the pure fluocarbon and the mixtures, respectively. It is found that viscosity isotherms for HFC-32 at subcritical temperatures exhibit a minimum with increasing pressure, with the viscosity decreasing as much as 10% relative to its value at one atmosphere. Correlations are presented for dilute gas viscosities, excess viscosities, and saturated liquid and vapor viscosities. These correlations are shown to lit our data within experimental uncertainties. For HFC-32/lubricant mixtures, a free-volume viscosity model has been applied to correlate the experimental data.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

HFC-161混合物替代R502的理论研究

提出一种新型制冷剂HFC-161/125/143a(质量百分比10/45/45)用于替代制冷剂R502.新制冷剂环境性能良好,ODP值为0,GWP值为3466,GWP值小于R502及其常用替代制冷剂R404A和R507.采用Refprop软件计算了HFC-161混合物的基本热物理性质,以及低温工况和变工况下的理论循环性能,并与制冷剂R502、R404A、R507的相关数据进行对比.结果表明:新制冷剂的运行压力、压比、COP值、单位容积制冷量与R502相当,温度滑移小于R502常用替代物R404A,是一种性能优良的制冷剂R502的替代物.     

Vapor–Liquid Equilibria of CFC Alternative Refrigerant Mixtures: Trifluoromethane (HFC-23)+Difluoromethane (HFC-32), Trifluoromethane (HFC-23)+Pentafluoroethane (HFC-125), and Pentafluoroethane (HFC-125)+1,1-Difluoroethane (HFC-152a)

Isothermal vapor–liquid equilibria for three binary mixtures of CFC alternative refrigerants were determined in an equilibrium apparatus in which both phases were continuously recirculated. The pressures and vapor and liquid compositions were measured for the binary systems trifluoromethane (HFC-23)+difluoromethane (HFC-32) and trifluoromethane (HFC-23)+pentafluoroethane (HFC-125) at 283.15 and 293.15 K and pentafluoroethane (HFC-125)+1,1-difluoroethane (HFC-152a) at 293.15 K. The experimental data were correlated with the Peng–Robinson–Stryjek–Vera equation of state using the Huron–Vidal original mixing rule. Calculated results with this equation showed good agreement with the experimental data.     

Liquid viscosities and densities of HFC-134a+glycol mixtures

Liquid viscosity and density of six binary mixtures of HFC-134a with glycols [ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (400), and polypropylene glycol (2000)] have been measured in the temperature range from 273 to 333 K. The viscosity was measured by a rolling-ball viscometer calibrated with standard liquids of viscosities and densities (JS5, JS10, JS20, and JS50). The density was measured with a glass pycnometer. The uncertainties of the measurements were estimated to be less than 3.4 % for viscosity and 0.04 % for density, respectively. An equation is given to represent the obtained viscosity values as a function of weight fraction and temperature.     

Correlation and Prediction of Dense Fluid Transport Coefficients. VIII. Mixtures of Alkyl Benzenes with Other Hydrocarbons

The aim of this article is to examine the application of the hard-sphere scheme to the prediction of the viscosity and thermal conductivity of hydrocarbon mixtures, other than n-alkane mixtures. According to this scheme, mixture properties are calculated from the pure components properties. Hence these are obtained first. Furthermore, in addition to the temperature, the density is the important parameter rather then the pressure. A Tait-type equation is employed to successfully correlate the density of the pure liquids. Furthermore, in the first part of this article, a modified form of the equation proposed by Sun and Teja is employed in the scheme, to correlate the viscosity and thermal conductivity of pure alkyl benzenes, some alkanes, some cycloalkanes, and one naphthalene. Following this, the article focuses on the successful prediction of the viscosity and thermal conductivity of mixtures of these compounds.     

Vapor–Liquid Equilibrium Measurements for Binary Mixtures Containing 1,1,1,2,3,3,3-Heptafluoropropane (HFC-227ea)1

Isothermal vapor–liquid equilibrium data for two binary mixtures of alternative refrigerants were determined by using an apparatus applying recirculating vapor and liquid. The difluoromethane (HFC-32)+1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and 1,1,1,2-tetrafluoroethane (HFC-134a)+1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) systems were studied at 298.15 and 312.65 K. The pressure and vapor and liquid compositions were measured at each temperature. The experimental data were correlated with the Peng–Robinson equation of state using the van der Waals one-fluid mixing rule. Calculated results show that this equation yields good agreement with the experimental data.     

Viscosity of Gaseous HFC-143a (1,1,1-trifluoroethane) Under High Pressures

The viscosity of gaseous HFC-143a(1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature under subcritical conditions or up to 9 MPa under supercritical conditions. Intermolecular potential parameters of HFC-143a for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation as functions of temperature and density is proposed to interpolate the present experimental results.