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.     

HFC-161及其应用

介绍ODs替代品HFC-161的性质及应用实例，通过分析与实验说明这些混合制冷剂能够分别替代R410A，R407C，R404A和HFC-134a，均具有环保性能优异、能效比高、用量少、与原系统兼容等特点。     

Ideal-Gas Heat Capacity Values and Equations for Hydrofluorocarbon (HFC) Refrigerants Based on Speed-of-Sound Measurements

Final values of ideal-gas heat capacity c ⁰ _p derived from speed-of-sound measurements using an acoustic spherical resonator and equations of c ⁰ _p as a simple function of temperature are provided from an overall assessment of speed-of-sound measurements for five hydrofluorocarbon (HFC) refrigerants, difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), and 1,1-difluoroethane (R152a). Some of the experimental results had systematic errors in comparison with theoretical calculations based on spectroscopic data, which seem to result from the impurity of the sample fluids. The agreement of the experimentally determined and theoretically calculated c ⁰ _p values was confirmed for HFC refrigerants. The uncertainty of c ⁰ _p values calculated from the proposed equations is estimated to be 0.1 or 0.2% corresponding to an ISO uncertainty with a coverage factor of k=1. An erratum for Table I in a previous report by Yokozeki et al. in 1999 is provided as an appendix.     

Saturated Liquid Viscosity and Surface Tension of Alternative Refrigerants

Light scattering by thermally excited capillary waves on liquid surfaces or interfaces can be used for the investigation of viscoelastic properties of fluids. In this work, we carried out the simultaneous determination of the surface tension and the liquid kinematic viscosity of some alternative refrigerants by surface light scattering (SLS) on a gas–liquid interface. The experiments are based on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). R23 (trifluoromethane), R32 (difluoromethane), R125 (pentafluoroethane), R143a (1,1,1-trifluoroethane), R134a (1,1,1,2-tetrafluoroethane), R152a (1,1-difluoroethane), and R123 (2,2-dichloro-1,1,1-trifluoroethane) were investigated under saturation conditions over a wide temperature range, from 233 K up to the critical point. It is estimated that the uncertainty of the present surface tension data for the whole temperature range is less than ±0.2 mN·m^–1. For temperatures up to about 0.95T _c, the kinematic viscosity of the liquid phase could be obtained with an absolute accuracy of better than 2%. For the highest temperatures studied in this work, measurements for the kinematic viscosity exhibit a maximum uncertainty of about ±4%. Viscosity and surface tension data are represented by a polynomial function of temperature and by a van der Waals-type surface tension equation, respectively. The results are discussed in detail with comparison to literature data.     

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.     

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.     

Prediction of the Thermal Conductivity and Viscosity of Binary and Ternary HFC Refrigerant Mixtures

A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous prediction of the thermal conductivity and the viscosity of binary and ternary HFC refrigerant mixtures, consisting of HFC-32, HFC-125, and HFC-134a. In this prediction scheme, the hypothetical molecular parameters of HFC refrigerant mixtures were assumed to be the molar average of the pure component values. The close agreement between the predicted values and the experimental results of thermal conductivity and viscosity demonstrate the predictive power of this scheme.     

板式蒸发器换热性能的数值模拟Ⅱ:结果及分析

在已建立的数学模型的基础上,对板式蒸发器换热能力进行了数值模拟.针对应用较广的R134a和R410A制冷剂来比较和分析板式蒸发器在小的温差下的换热性能.在三种不同的计算工况下简要分析了各种热力参数的变化对蒸发器整体换热性能的影响.不同的制冷剂,其换热系数和压降差别较大,相同工况下采用R410A替代R22,板式蒸发器的换热性能可提高8.5%～10.0%,且压降可大幅降低.     

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.     

Pseudo-Pure Fluid Equations of State for the Refrigerant Blends R-410A, R-404A, R-507A, and R-407C

Pseudo-pure fluid equations of state explicit in Helmholtz energy have been developed to permit rapid calculation of the thermodynamic properties of the refrigerant blends R-410A, R-404A, R-507A, and R-407C. The equations were fitted to values calculated from a mixture model developed in previous work for mixtures of R-32, R-125, R-134a, and R-143a. The equations may be used to calculate the single-phase thermodynamic properties of the blends; dew and bubble point properties are calculated with the aid of additional ancillary equations for the saturation pressures. Differences between calculations from the pseudo-pure fluid equations and the full mixture model are on average 0.01%, with all calculations less than 0.1% in density except in the critical region. For the heat capacity and speed of sound, differences are on average 0.1% with maximum differences of 0.5%. Generally, these differences are consistent with the accuracy of available experimental data for the mixtures, and comparisons are given to selected experimental values to verify accuracy estimates. The equations are valid from 200 to 450 K and can be extrapolated to higher temperatures. Computations from the new equations are up to 100 times faster for phase equilibria at a given temperature and 5 times faster for single-phase state points given input conditions of temperature and pressure.     

R404A和R410A应用于平行流冷凝器的模拟分析比较

采用分布参数法对平行流冷凝器建立数学模型，对目前广泛使用的制冷剂R134a和低温制冷剂R404A和R410A在平行流冷凝器中的换热和流动性能进行模拟计算和分析比较。分别在相同和不同工况下。比较3种制冷剂的换热系数及压降等换热和流动性能参数。结果表明，在采用平行流冷凝器的汽车空调工况范围内，R410AR404A的流动和传热性能均优于R134a，更适宜用于汽车空调用平行流冷凝器。     

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.     

冷冻冷藏用制冷剂R404A的替代品对比分析

基于现有的R404A涡旋式压缩机,模拟分别采用R404A,R407A,R407F,R134a和R1234ze制冷剂时的压缩机性能,计算5种制冷剂系统的理论循环COP,并对各典型工况进行对比分析。计算结果表明,R407A和R407F可直接应用于R404A压缩机,而R134a和R1234ze替代R404A时压缩机设计变更较大,4种制冷剂系统能效均较R404A系统有较大提高。     

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

The liquid thermal conductivity of two ternary mixtures of HFC-32/125/134a (23.0/25.0/52.0 and 19.0/43.8/37.2 wt%) was measured using a transient hot-wire instrument in the temperature ranges from 193 to 293 K and from 213 to 293 K, respectively, and in the pressure range from 2 to 30 MPa. The thermal conductivity has an estimated uncertainty of ±0.7%. For engineering purposes, the thermal conductivity data were correlated using a polynomial in temperature and pressure for each mixture with a standard deviation of 0.6%.     

Capillary tube selection for HCFC22 alternativesSélection de capillaires pour les frigorigènes de remplacement du HCFC22

In this paper, pressure drop through a capillary tube is modeled in an attempt to predict the size of capillary tubes used in residential air conditioners and also to provide simple correlating equations for practicing engineers. Stoecker's basic model was modified with the consideration of various effects due to subcooling, area contraction, different equations for viscosity and friction factor, and finally mixture effect. McAdams' equation for the two-phase viscosity and Stoecker's equation for the friction factor yielded the best results among various equations. With these equations, the modified model yielded the performance data that are comparable to those in the ASHRAE handbook. After the model was validated with experimental data for CFC12, HFC134a, HCFC22, and R407C, performance data were generated for HCFC22 and its alternatives, HFC134a, R407C, and R410A under the following conditions: condensing temperature; 40, 45, 50, 55°C, subcooling; 0, 2.5, 5°C, capillary tube diameter; 1.2–2.4 mm, mass flow rate; 5–50 g/s. These data showed that the capillary tube length varies uniformly with the changes in condensing temperature and subcooling. Finally, a regression analysis was performed to determine the dependence of mass flow rate on the length and diameter of a capillary tube, condensing temperature, and subcooling. Thus determined simple practical equations yielded a mean deviation of 2.4% for 1488 data obtained for two pure and two mixed refrigerants examined in this study.     

Refrigeration system performance using liquid-suction heat exchangersPerformance d''un système frigorifique utilisant des échangeurs liquide-vapeur à l''aspiration

Heat transfer devices are provided in many refrigeration systems to exchange energy between the cool gaseous refrigerant leaving the evaporator and warm liquid refrigerant exiting the condenser. These liquid-suction or suction-line heat exchangers can, in some cases, yield improved system performance while in other cases they degrade system performance. Although previous researchers have investigated performance of liquid-suction heat exchangers, this study can be distinguished from the previous studies in three ways. First, this paper identifies a new dimensionless group to correlate performance impacts attributable to liquid-suction heat exchangers. Second, the paper extends previous analyses to include new refrigerants. Third, the analysis includes the impact of pressure drops through the liquid-suction heat exchanger on system performance. It is shown that reliance on simplified analysis techniques can lead to inaccurate conclusions regarding the impact of liquid-suction heat exchangers on refrigeration system performance. From detailed analyses, it can be concluded that liquid-suction heat exchangers that have a minimal pressure loss on the low pressure side are useful for systems using R507A, R134a, R12, R404A, R290, R407C, R600, and R410A. The liquid-suction heat exchanger is detrimental to system performance in systems using R22, R32, and R717.     

Nucleate boiling heat transfer coefficients of HCFC22, HFC134a, HFC125, and HFC32 on various enhanced tubes

In this study, nucleate boiling heat transfer coefficients (HTCs) of HCFC22, HFC134a, HFC125, HFC32 were measured on a low fin, Turbo-B, and Thermoexcel-E tubes. All data were taken at the liquid pool temperature of 7 °C on horizontal tubes of 152 mm length and 18.6–18.8 mm outside diameter at heat fluxes of 10–80 kW m⁻² with an interval of 10 kW m⁻² in the decreasing order of heat flux. For a plain and low fin tubes, refrigerants with higher vapor pressures showed higher nucleate boiling HTCs consistently. This was due to the fact that the wall superheat required to activate given size cavities became smaller as pressure increased. For Turbo-B and Thermoexcel-E tubes, HFC125 showed a peculiar behavior exhibiting much reduced HTCs due to its high reduced pressure. The heat transfer enhancement ratios of the low fin, Turbo-B, and Thermoexcel-E tubes were 1.09–1.68, 1.77–5.41, 1.64–8.77 respectively in the range of heat fluxes tested.     

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.     

Vapor–Liquid Critical Surface of Ternary Difluoromethane+Pentafluoroethane+1,1,1,2-Tetrafluoroethane (R-32/125/134a) Mixtures

The plane of vapor–liquid criticality for ternary refrigerant mixtures of difluoromethane (R-32)+pentafluoroethane (R-125)+1,1,1,2-tetrafluoroethane (R-134a) was determined from data on the vapor–liquid coexistence curve near the mixture critical points. The compositions (mass percentage) of the mixtures studied were 23% R-32+25% R-125+52% R-134a (R-407C), 25% R-32+15% R-125+60% R-134a (R-407E), and 20% R-32+40% R-125+40% R-134a (R-407A). The critical temperature of each mixture was determined by observation of the disappearance of the meniscus. The critical density of each mixture was determined on the basis of meniscus disappearance level and the intensity of the critical opalescence. The uncertainties of the temperature, density, and composition measurements are estimated as ±10 mK, ±5 kg·m^–3, and ±0.05%, respectively. In addition, predictive methods for the critical parameters of R-32/125/134a mixtures are discussed.     

我国空调用制冷剂回收再生的机遇与挑战

中国是全世界最大的制冷设备与制冷剂生产国和消费国,全球制冷剂超过1/3的需求量来自中国。预计至2030年,我国制冷空调行业制冷剂消费总量将达15.4~17.8万吨。本文介绍了国内外制冷剂回收再生技术及设备现状;调研了国内外对于制冷剂回收、净化再利用的相关标准,以及制冷剂中不同污染物含量的检测方法;分析了常用的传统制冷剂碳排放评价指标及优缺点,探讨了一种适合制冷剂回收再生过程的制冷剂气候性能评估指标;提出制冷剂回收、净化再利用的机遇与挑战。