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.     

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%.     

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%.     

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.     

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.     

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.     

The thermal conductivity of R22, R142b,R152a,and their mixtures in the liquid state

An experimental apparatus for measuring the thermal conductivity of liquids by the transient hot-wire method was constructed and tested with toluene as a standard liquid. Measurements were performed on R22, R142b, and R152a. The thermal conductivities of mixtures of R142b and R152a with R22 were also measured by varying the weight fraction of R22. Experiments were performed in the range from –50 to 50°C and from 2 to 20 MPa and the measured data are analyzed to obtain a correlation in terms of temperature, pressure, and composition of the mixture. While the thermal conductivity of R22 + R152a mixtures varies monotonously with composition, that of R22 + R142b mixtures turned out to go through an extremum value. The accuracy of our measurements is estimated to be within 2%.Paper dedicated to Professor Joseph Kestin.     

Measurements of the viscosity of R11, R12, R141b,and R152a in the temperature range 270–340 K at pressures up to 20 MPa

This paper reports new measurements of the liquid viscosity of R11, R12, R1416, and R152a 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. A recently developed semiempirical scheme, based on considerations of hard-sphere theory, is employed to correlate successfully the viscosity and the thermal conductivity of these refrigerants as a function of their density.     

Thermal conductivity of R134a and R141b within the temperature range 240–307 K at the saturation vapor pressure

New, absolute values of the thermal conductivity of two refrigerants, R134a and R141b, in the liquid phase at saturation are reported. The measurements have been performed in transient hot-wire instruments making use of electrically insulated tantalum wires within the temperature range 240–307 K. The results are estimated to have an accuracy of ±1%.     

Measurements of the thermal conductivity of R11 and R12 in the temperature range 250–340 K at pressures up to 30 MPa

This paper reports new, absolute measurements of the thermal conductivity of liquid refrigerants R11 and R12 in the temperature range 250–340 K at pressures from saturation up to 30 MPa. The measurements, performed in a new transient hot-wire instrument employing two anodized tantalum wires, have an estimated uncertainty of ±0.5%. Measurements of the thermal conductivity of toluene in the temperature range 250–340 K at pressures up to 30 MPa are also reported.     

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.     

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 conductivities of new refrigerants R125 and R32 measured by the transient hot-wire method

Thermal conductivity measurements are reported for the new refrigerants pentafluoroethane (R125) and dilluoromethane (R32), which are suggested to replace chlorodifluoroethane (R22) as components of a mixture. Transient hot-wire experiments were performed which cover both the liquid and the vapor states at temperatures and pressures ranging fromt = –40 to 90°C and fromp = 1 to 60 bar. Uncertainties keep within 1.6% for liquid and 2.0% for vapor states, The results are correlated with density and temperature. In addition, temperature-dependent correlations are presented for practical calculations for (i) saturated liquid, (ii) saturated vapor, and (iii) dilute gas (which approximately equals the vapor state at ambient pressure). Finally, the results are compared with data from the literature and also with the respective thermal conductivities of R22.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Experimental evaluation of refrigerant mixtures as substitutes for CFC12 and R502

Several selected refrigerant mixtures are tested as potential short- and mid-term substitutes for CFC12 and R502. HCFC22 and some hydrocarbons are considered as components of retrofit mixtures. Their influence on the solubility of various lubricant oils is investigated by measuring critical solubility temperatures. The performance of the CFC12 and R502 refrigerants and of their proposed alternatives is compared by testing two different refrigerating units.     

Performance and heat transfer characteristics of hydrocarbon refrigerants in a heat pump systemPerformance et caractéristiques de transfert de chaleur des frigorigènes hydrocarbures utilisés dans un système de pompe à chaleur

Performance of a heat pump system using hydrocarbon refrigerants has been investigated experimentally. Single component hydrocarbon refrigerants (propane, isobutane, butane and propylene) and binary mixtures of propane/isobutane and propane/butane are considered as working fluids in a heat pump system. The heat pump system consists of compressor, condenser, evaporator, and expansion device with auxiliary facilities such as evacuating and charging unit, the secondary heat transfer fluid circulation unit, and several measurement units. Performance of each refrigerant is compared at several compressor speeds and temperature levels of the secondary heat transfer fluid. Coefficient of performance (COP) and cooling/heating capacity of hydrocarbon refrigerants are presented. Experimental results show that some hydrocarbon refrigerants are comparable to R22. Condensation and evaporation heat transfer coefficients of selected refrigerants are obtained from overall conductance measurements for subsections of heat exchangers, and compared with those of R22. It is found that heat transfer is degraded for hydrocarbon refrigerant mixtures due to composition variation with phase change. Empirical correlations to estimate heat transfer coefficients for pure and mixed hydrocarbons are developed, and they show good agreement with experimental data. Some hydrocarbon refrigerants have better performance characteristics than R22.     

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.     

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.     

R32和R410A循环特性对比研究

国内外加速淘汰 HCFCs 制冷剂的时间表已经确定,而理想的替代制冷剂仍不明确.本文以风冷式冷(热)水机组为对象,对目前业内应用较多的替代制冷剂 R410A 以及被国内学者关注的制冷剂 R32 的循环特性进行理论分析及实验研究,并指出应用 R32 制冷剂时存在的问题,以期为国内 R22 的替代决策提供有益的参考.     

Vapour-liquid equilibrium of ternary mixtures of the refrigerants R125, R143a and R134a

Apart from ternary mixtures of R32 with R125 and R134a, similar mixtures with R143a instead of R32 are discussed as alternatives to the widely used refrigerants R22 and R502. In the present work, the phase equilibrium of such ternary mixtures is described by simple cubic equations of state which are based only on experimental data for the pure substances and for a nearly equimolar mixture of every binary system.In addition to previous experimental investigations the critical properties and the saturation pressure were measured for pure R143a and for nearly equimolar mixtures of the binary systems and . The temperature ranged from −70°C up to the respective critical point. The validity of the resulting equations of state for ternary mixtures of R125, R143a and R134a is confirmed by comparison with experimental results of the vapour-liquid equilibrium for a mixture with about 17mol% of R125 and R143a, respectively, and about 66mol% of R134a.     

R22替代工质回热循环的性能分析

R22的替代工质的制冷性能通常比R22差，采用回热循环是改善循环性能的一种方法，但是增加回热器会带来成本的增加，而且不同的制冷剂在回热循环中的COP及容积制冷量的变化也是不同的。针对上述问题，分析回热循环的特性和6种制冷剂（R290，R1270，R134a／R1270（0．45／0．55），R134a／R290（0．6／0．4），R407C和R410A）在回热循环中的容积制冷量和COP的变化特点。研究结果表明，R134a,／R1270，R290和R134a／R290系统使用回热器后，性能改善较大，R410A系统只有在高冷凝温度、高过热度时才有必要使用回热器，其余替代工质系统使用回热器，其系统性能改善不明显。