Liquid thermal conductivity of binary mixtures of difluoromethane (R32) and pentafluoroethane (R125)

The thermal conductivities of refrigerant mixtures of difluoromethane (R32) and pentafluoroethane (R125) in the liquid phase are presented. The thermal conductivities were measured with the transient hot-wire method with one bare platinum wire. The experiments were conducted in the temperature range of 233–323 K and in the pressure range of 2–20 MPa. An empirical equation to describe the thermal conductivity of a near-azeotropic mixture, R32+R125, is provided based on the measured 168 thermal conductivity data as a function of temperature and pressure. The dependence of thermal conductivity on the composition at different temperatures and pressures is also presented. The uncertainty of our measurements is estimated to be ±2%. Paper dedicated to Professor Edward A. Mason.     

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%.     

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.     

Thermal Conductivity of the Refrigerant Mixtures R404A, R407C, R410A, and R507A

New thermal conductivity data of the refrigerant mixtures R404A, R407C, R410A, and R507C are presented. For all these refrigerants, the thermal conductivity was measured in the vapor phase at atmospheric pressure over a temperature range from 250 to 400 K and also at moderate pressures. A modified steady-state hot-wire method was used for these measurements. The cumulative correction for end effects, eccentricity of the wire, and radiation heat transfer did not exceed 2%. Calculated uncertainties in experimental thermal conductivity are, in general, less than ±1.5%. All available literature thermal conductivity data for R404A, R407C, R410A, and R507C were evaluated to identify the most accurate data on which to base the thermal conductivity model. The thermal conductivity is modeled with the residual concept. In this representation, the thermal conductivity was composed of two contributions: a dilute gas term which is a function only of temperature and a residual term which is a function only of density. The models cover a wide range of conditions except for the region of the thermal conductivity critical enhancement. The resulting correlations are applicable for the thermal conductivity of dilute gas, superheated vapor, and saturated liquid and vapor far away from the critical point. Comparisons are made for all available literature data.     

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 a wide range of alternative refrigerants measured with an improved guarded hot-plate apparatus

The thermal conductivity of the refrigerants R22, R123, R134a, R142b, R143a, and R152a has been determined as a function of temperature in the range from 300 to 460 K. Measurements were carried out at atmospheric pressure with an improved guarded hot-plate apparatus. The width of the instrument's gas layer and the temperature difference across the metering section were varied to detect any stray heat transfer. Radiation correction factors were derived from IR absorption spectra. The uncertainty of the measurements is estimated to be 2% at a standard deviation of less than 0.1%. All values are correlated with respect to temperature in the range covered. The equations are found to represent the results with average deviations of 1%. Our data sets are compared with corresponding hot wire results. In contrast to the generally preferred hot wire technique, with its possible electrical and chemical interactions between the wire and the polar refrigerant, there are no such difficulties using a guarded hot-plate apparatus. Our data sets may thus contribute to the discussions on discrepancies in thermal conductivity values from various authors using hot wire as one particular method.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, USA.     

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%.     

Thermal conductivity of gaseous fluorocarbon refrigerants R 12, R 13, R 22, and R 23, under pressure

The thermal conductivity of four gaseous fluorocarbon refrigerants has been measured by a vertical coaxial cylinder apparatus on a relative basis. The fluorocarbon refrigerants used and the ranges of temperature and pressure covered are as follows: R 12 (Dichlorodifluoromethane CCl₂F₂): 298.15–393.15 K, 0.1–4.28 MPa R 13 (Chlorotrifluoromethane CClF₃): 283.15–373.15 K, 0.1–6.96 MPa R 22 (Chlorodifluoromethane CHClF₂): 298.15–393.15 K, 0.1–5.76 MPa R 23 (Trifluoromethane CHF₃): 283.15–373.15 K, 0.1–6.96 MPaThe apparatus was calibrated using Ar, N₂, and CO₂ as the standard gases. The uncertainty of the experimental data is estimated to be within 2%, except in the critical region. The behavior of the thermal conductivity for these fluorocarbons is quite similar; thermal conductivity increases with increasing pressure. The temperature coefficient of thermal conductivity at constant pressure, (/T) _p , is positive at low pressures and becomes negative at high pressures. Therefore, the thermal conductivity isotherms of each refrigerant intersect each other in a specific range of pressure. A steep enhancement of thermal conductivity is observed near the critical point. The experimental results are statistically analyzed and the thermal conductivities are expressed as functions of temperature and pressure and of temperature and density.     

Measurements of the thermal conductivity of R22, R123, and R134a in the temperature range 250–340 K at pressures up to 30 MPa

This paper reports new, absolute measurements of the thermal conductivity of the liquid refrigerants R22, R123, and R134a in the temperature range 250–340 K at pressures from saturation up to 30 MPa. The measurements, performed in a transient hot-wire instrument employing two anodized tantalum wires as the heat source, have an estimated uncertainty of ±0.5%. A recently developed semiempirical scheme is employed to correlate successfully the thermal conductivity and the viscosity of these refrigerants, as a function of their density.     

Measurements of the thermal conductivity of liquid R32, R124, R125, and R141b

This paper reports measurements of the thermal conductivity of refrigerants R32, R124, R125, and R141b in the liquid phase. The measurements, covering a temperature range from 253 to 334 K and pressure up to 20 MPa, have been performed in a transient hotwire instrument employing two anodized tantalum wires. The uncertainty of the present thermal-conductivity data is estimated to be ±0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation. A comparison with other recent measurements is also included.     

Measurement of vapor viscosity of R1234yf and its binary mixtures with R32, R125

The vapor viscosities of the new refrigerant R1234yf and its binary mixtures, R32+R1234yf, R125+R1234yf, were measured at atmospheric pressure with a falling-ball-type viscometer. The combined expanded uncertainty of the measurement apparatus was less than 1.5%. The binary mixtures consisted of 20.0, 30.0, 40.0, and 50.0 wt% R32 for R32+R1234yf and of 20.0, 35.0, 50.0, and 70.0 wt% R125 for R125+R1234yf. The viscosities of R1234yf were correlated with the Chapman–Enskog gas kinetic theory and those of binary mixtures were correlated with the Wilke mixture rule. The average absolute deviation (AAD) is 0.189% for R32+R1234yf and 1.169% for R125+R1234yf. The deviations of experimental viscosities of the binary mixtures from data calculated using RefProp v9.1 were also obtained. The AAD is 0.555% for R32+R1234yf and 1.479% for R125+R1234yf.     

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.     

Flow-boiling of R22, R134a, R507, R404A and R410A inside a smooth horizontal tube

Flow boiling heat transfer coefficients of R22, R134a, R507, R404A and R410A inside a smooth horizontal tube (6 mm I.D., 6 m length) were measured at a refrigerant mass flux of about 360 kg/m² s varying the evaporating pressure within the range 3–12 bar, with heat fluxes within the range 11–21 kW/m². The experimental data are discussed in terms of the heat transfer coefficients as a function of the vapour quality. The experimental results clearly show that the heat transfer coefficients of R134a are always higher than those pertaining to R22 (from a minimum of +6 to a maximum of +45%).     

Viscosity of refrigerants R12, R113, and R114 and mixtures of R12 + R114 at high pressure

New viscosity measurements for the gaseous and supercritical state of the halogenated hydrocarbons R12, R113, and R114 and binary mixtures of R12 + R114 of different compositions are presented. The measurements were carried out at superheated and supercritical temperatures from 30 to 200° C and in the pressure range from 1 to 80 bar. Viscosity was measured with an oscillating-disk viscometer and the data obtained are relative to the viscosity of nitrogen. The estimated accuracy of the measured results is ±0.6%. The results obtained show that, at subcritical temperatures, the pressure effect on viscosity is negative. This anomalous behaviour is investigated in detail in this work. At atmospheric pressure the viscosity of gas mixtures is almost a linear function of their composition. At high pressure, the residual viscosities - ₀ of both the pure components and the mixtures were used to follow a single relationship versus the residual reduced density _r0.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

The surface tension of HFC refrigerants and mixtures

The surface tension of the refrigerants R32, R125, R134a, R143a and R152a, as well as the binary refrigerant mixtures R32-R125, R32-R134a, R125-R134a, R125-R143a, R125- R152a, R143a-R134a and R134a-R152a, and the commercially available ternary mixtures R404A and R407C was measured across the temperature range from −50 to 60°C using a measuring unit based on the capillary rise method. Different formulations for calculation of the surface tension of the binary and ternary mixtures on the basis of the surface tension of the pure refrigerants were tested. With an approach based on mass proportions in the mixture, a good correspondence between the measured and calculated values was achieved.     

Viscosity of Gaseous R404A, R407C, R410A, and R507

This paper presents new measurements of the viscosity of gaseous R404A (52 wt% R143a, 44 wt% R125, 4 wt% R134a), R407C (23 wt% R32, 25 wt% R125, 52 wt% R143a), R410A (50 wt% R32, 50 wt% R125), and R507 (50 wt% R143a, 50 wt% R125). These mixtures are recommended as substitutes for the refrigerants R22, R502, and R13B1. Measurements were carried out in an oscillating-disk viscometer. The obtained values of the viscosity are relative to the viscosity of nitrogen. The experiments were performed at atmospheric pressure over the temperature range 297 to 403 K. and near the saturation line up to pressures of 0.6 P _crit. The estimated uncertainty of the reported viscosities are ±0.5% for the viscosities at atmospheric pressure and ± 1% along the saturation line, being limited by the accuracy of the available vapor pressure and density data. The experimental viscosities at atmospheric pressure are employed to determine the intermolecular potential parameters, and , which provide the optimum representation of the data with the aid of the extended law of corresponding states developed by Kestin et al. A comparison of the experimental viscosity data with the values calculated by REFPROP, both at atmospheric pressure and along the saturation line, is presented.     

Performances d'une machine tritherme à éjecteur utilisant des mélanges de fluides frigorigènesPerformance analysis of a jet cooling system using refrigerant mixtures

The optimisation of a jet cooling system using refrigerant mixtures as substitutes of pure refrigerants has been investigated. A steady-state simulation program, for given temperatures of the sources, integrating simple models of each component has been developed. A Peng-Robinson equation of state assuming equality of the fugacities of the two phases was used to model the thermodynamic properties of the vapour and liquid-vapour equilibrium. The refrigerants investigated in this study are: the pure refrigerants R142b, R152a, RC318, R124, R134a, R22 and the binary refrigerants R22/RC318, R22/R142b, R22/R124, R22/R152a, R22/R134a, R134a/R142b, R152a/R142b and R134a/R152a. Results show that the use of a binary mixture does not always increase the performance of system. Generally, when the mixture is strongly zeotropic (e.g.: R22/RC318), the cooling efficiency of the system decreases. However, when the mixture is mildly zeotropic (e.g. R134a/R142b) or almost azeotropic (e.g. R134a/R152a), efficiency and energetic efficiency increase.     

Shear viscosity and thermal conductivity of dipolar real fluids from equilibrium molecular dynamics simulation

Equilibrium molecular dynamics and the Green-Kubo formalism were used to simultaneously calculate shear viscosity and thermal conductivity for 10 refrigerants: R11, R12, R22, R23, R41, R123, R134a, R142b, R143a, and R152a. The fluids were modelled in previous work of Stoll et al. [J Chem Phys 2003;119:11396-407] using the two-center Lennard-Jones plus point dipole (2CLJD) pair potential, with parameters adjusted to vapor-liquid equilibria only. The predicted shear viscosities and thermal conductivities show an overall average deviation of about 15% and 10%, respectively, from correlations of experimental data.     

Thermal conductivity of gaseous HFC-134a,HFC-143a,HCFC-141b,and HCFC-142b

The thermal conductivity of new environmentally acceptable fluorocarbons HFC-134a (CH₂FCF₃), HFC-143a (CH₃CF₃), HCFC-141b (CH₃CCl₂F), and HCFC-142b (CH₃CCl₂F) in the gaseous phase has been measured in the temperature range 293–353 K at pressures up to 4 MPa. The thermal conductivity has been measured with a coaxial-cylinder cell on a relative basis. The apparatus was calibrated with He, Ne, Ar, Kr, N₂, CH₄, and SF₆ as reference fluids. The uncertainty of the experimental data obtained is estimated to be within 2% except for the uncertainty associated with the reference thermal-conductivity values. The excess thermal conductivity has been correlated satisfactorily as a function of density.