Differential Capillary Rise Method Research Articles

Surface tension measurement and molecular simulation for new low global warming potential refrigerants R1132(E) and R1132a

This study performed surface tension measurements assisted by molecular simulations for new candidate refrigerants R1132(E) and its isomer R1132a, which exhibit extremely low global warming potentials. Because the measured saturation density required for the surface tension measurement by the differential capillary rise method is insufficient at low temperatures, the density data was extrapolated by molecular simulations. In the process, quantum chemical and molecular dynamics simulations were performed to reproduce the vapor–liquid equilibrium state, and the accuracy of the obtained molecular force fields was verified by comparing them with the measured data. Based on the obtained surface tension data, validated temperature correlation equations were proposed for R1132(E) and R1132a, respectively, validated in the temperature range from 209 K to 225 K. Furthermore, their parachors, which relate surface tension to saturation density, were determined from the above data as 116.1 and 116.7 for R1132(E) and R1132a, respectively.

Molecular simulation and experimental validation for surface tension of new Low-GWP refrigerant mixtures R32/CF3I and R1123/CF3I

This study demonstrated a new procedure for measuring surface tension using molecular dynamics (MD) simulations. The surface tension was measured by the differential capillary rise method for refrigerant mixtures R1123/CF3I and R32/CF3I, which have a low global warming potential. The information of the saturated density in the low-temperature region, which was necessary for data reduction, was supplemented by an MD simulation, which was validated using accurate measurement data near the critical point. The surface tension calculated from the pressure tensor obtained by the MD simulation deviated considerably. However, the surface tension obtained from the simulated density and composition in the vapor and liquid phases by the parachor method was in agreement with the measured values within the measurement uncertainty ranges from 0.15 mNm−1 to 0.35 mNm−1. The simulated density distribution showed positive surface activity at the vapor–liquid interface, indicating that R32 and R1123, with smaller polarities, tended to aggregate on the liquid surface. This helps interpret the empirically postulated decrease in the surface tension of the mixtures due to the concentration of substances with lower surface tension at the vapor–liquid interface.

Experimental investigation on the surface tension of R1243zf with POE lubricants from 283 K to 343 K

The surface tension of the refrigerant-lubricant mixture is an essential parameter for the optimization of the refrigeration system. In this work, the surface tension of pure 3,3,3-trifluoropropene (R1243zf) and its mixtures with three POE lubricants including SL32S, POE68, and RL68H were measured using the differential capillary rise method at temperatures ranging from 283.15 K to 343.15 K. The experimental data of the mixtures were correlated as a function of lubricant mass fraction and temperature. The average absolute deviations between experimental results and calculated values for R1243zf/SL32S, R1243zf/POE68, and R1243zf/RL68H are 0.042 mN·m−1, 0.050 mN·m−1 and 0.046 mN·m−1, respectively.

Interfacial tension measurements of methane + propane binary and methane + propane + n-heptane ternary mixtures at low temperatures

The interfacial tension (IFT) between a liquid and a gas is essential in the design of liquid-gas separators as it determines the size of liquid droplets which can become entrained in the gas phase. In liquefied natural gas (LNG) plants, the scrub column is designed to remove components heavier than propane. However, if this column is poorly designed, these heavier components can carry over in the top product and potentially cause a solids formation problem in the main cryogenic heat exchanger. Therefore, accurate measurements and predictions of IFT are required to ensure good separation of heavy components prior to the liquefaction of the natural gas. In this work, reference-quality IFT measurements of methane + propane binary mixtures and methane + propane + n-heptane ternary mixtures were conducted at low temperatures (204 to 230) K and pressures up to the mixtures’ critical points using the differential capillary rise method in a high-pressure visual sapphire cell. The combined standard absolute uncertainties of the measured IFT were between (0.04 and 0.96) mN·m−1. The absolute deviations of measured IFT from values predicted with a Parachor model were within 3 mN⋅m−1, while a Linear Gradient Theory model over predicts mixtures’ IFT by up to 5.2 mN⋅m−1. The reference-quality IFT experimental data provided by this work should facilitate improvements of prediction models and allow separators in LNG plants to be designed with more confidence.

Surface tension and parachor for a new low-GWP refrigerant R1123/R32/R1234yf and its constituent binary pairs

Trifluoroethene R1123 is expected to be a low GWP refrigerant; however, it needs to be mixed with other stable refrigerants to avoid a disproportional reaction. This paper delivers one of the essential thermophysical properties surface tension for a low-GWP refrigerant mixture R1123/R32/1234yf measured by the differential capillary rise method in the temperature range from 225 to 345 K. The propagated uncertainty in surface tension with a 95% confidence level was typically 0.15 mNm−1. From the measured surface tension and calculated saturation densities, the parachor of R32 and R1123 were determined to be 91.6 and 123.3, respectively. The parachor of R1234yf was slightly dependent on a temperature, T, as 181.44−0.0319T. The variation in the surface tension of binary pairs against the composition was predicted by the correlation proposed by Di Nicola et al. (2018) and the parachor method with sufficient accuracy. Furthermore, the surface tension of ternary mixture R1123/R32/1234yf at compositions of 60/22/18 mass% and 22/70/08 mass% was also predicted by the parachor method with sufficient accuracy. Nevertheless, a slight deviation was confirmed at temperatures below 260 K. The prediction would be improved with subsequent studies in phase equilibrium. (191 words).

Surface Tension Measurement for a New Low-GWP Refrigerant HFO-1123 by a Differential Capillary Rise Method

Surface Tension Measurement for a New Low-GWP Refrigerant HFO-1123 by a Differential Capillary Rise Method

Measurements of Surface Tension of R1234yf and R1234ze(E)

An experimental apparatus based on the differential capillary rise method for measuring the surface tension was built up and verified. The surface tensions of R1234yf and R1234ze(E) were measured from 242 to 365 K and 242 to 380 K, respectively. The surface tension data were correlated as a function of temperature, and the average absolute deviations between the experimental and calculated values were 0.002 mN·m–1 for R1234yf, and 0.009 mN·m–1 for R1234ze(E). The surface tension data at temperature lower than 273 K was first reported.

Surface tension of HFC-161 and compressor oil mixtures

The surface tension of environmental-protection refrigerant ethyl fluoride (HFC-161) and its mixtures with commercial lubricant RL68H, SUNISO SL-32S and SUNISO 3GS were determined in the temperature range from (242 to 370)K by differential capillary rise method. The mass fraction of oil in mixtures is below 2.0%. All the surface tensions of mixtures were correlated as a function of temperature and mass fractions, which can be easy to apply to relevant refrigeration design. Before that, the experimental apparatus was verified by measuring the surface tension of HC-600a. The temperature and surface tension uncertainty were within 12mK, 0.2mN ⋅ m−1, respectively.

Surface tension and liquid viscosity measurement of ethyl fluoride (R161) under saturation condition

Surface light scattering (SLS) has been used for the simultaneous determination of surface tension and liquid kinematic viscosity of ethyl fluoride (R161) under saturation conditions in the temperature ranges between 293K and very close to the critical temperature with the expanded uncertainties(k=2) of ±2% for the liquid kinematic viscosity and ±1.5% for the surface tension. In addition, the surface tension of R161 was also measured over the temperature range from (244 to 334)K using the differential capillary rise method. All the surface tension and viscosity results were correlated as a function of temperature, and the average absolute deviations between the experimental and calculated values were 0.04mNm−1 and 1.11%, respectively.

Surface tension of low GWP refrigerants R1243zf, R1234ze(Z), and R1233zd(E)

The surface tension of R1243zf, R1234ze(Z), and R1233zd(E) were measured at temperatures from 270 K to 360 K by an experimental apparatus based on the differential capillary rise method. The deviation between the measured surface tension of R134a and R245fa and the calculated surface tension with REFPROP 9.1 (Lemmon et al., 2013) was ±0.13 mN m−1, which is less than the estimated propagated uncertainty in surface tension of ±0.2 mN m−1. Eleven points, thirteen points, and ten points of surface tension data were provided for R1243zf, R1234ze(Z), and R1233zd(E), respectively, in this paper. The measured data and the estimated surface tension using the methods of Miller (1963), Miqueu et al. (2000), and Di Nicola et al. (2011) agree within the standard deviation of ±0.43 mN m−1. The empirical correlations that represent the measured data within ±0.14 mN m−1 were proposed for each refrigerant.

Surface tension of ethyl fluoride (HFC161) from (233 to 373) K

The surface tension of ethyl fluoride (R161) was measured over the temperature range from (233 to 373)K with a differential capillary rise method, together with the surface tension of isobutane (R600a) measured in the temperature range from (275 to 343)K for verifying the experimental system. The temperature and surface tension uncertainties were estimated to be within ±20mK and ±0.2mNm−1 respectively. The surface tension values of R161 were correlated as a function of temperature with an average absolute deviation of 0.043mNm−1.

Surface tension of dimethyl ether + propane from 243 to 333 K

The surface tension of the binary refrigerant mixture dimethyl ether (RE170)(1) + propane (R290)(2) at three mass fraction of w 1 = 0.3007,0.4975 and 0.6949 was measured in the temperature range from 243 to 333 K with a differential capillary rise method. The uncertainties of the measurement of the temperature and the surface tension were estimated to be within ±10 mK and ±0.2 mN m −1, respectively. A correlation for the surface tension of the binary refrigerant mixture RE170 + R290 was developed as a function of the composition.

Surface tension of diethyl carbonate, 1,2-dimethoxyethane and diethyl adipate

The surface tension was investigated with a differential capillary rise method in the temperature range from 273 to 373 K for diethyl carbonate, 278 to 373 K for 1,2-dimethoxyethane, and 293 to 373 K for diethyl adipate, respectively. The uncertainties of the temperature and surface tension were estimated to be within ±10 mK and ±0.2 mN m −1, respectively. A surface tension correlation was developed as a function of temperature with the experimental data, and the average absolute deviations were 0.04, 0.07 and 0.09 mN m −1 for diethyl carbonate, 1,2-dimethoxyethane and diethyl adipate, respectively.

Surface Tension of Propane (R-290) + 1,1-Difluoroethane (R-152a) from (248 to 328) K

The surface tension of binary mixture refrigerants propane (R-290) (1) + 1,1-difluoroethane (R-152a) (2) at three mass fractions of w1 = 0.2008, 0.3497, and 0.4922 was measured at temperatures from (248 to 328) K with a differential capillary rise method. The uncertainties of measurements for the temperature and surface tension were estimated to be within ± 10 mK and ± 0.2 mN·m−1, respectively. A correlation for the binary mixture refrigerant R-290 + R-152a was developed as a function of mass fraction.

Surface Tension of Diethyl Ether, Diisopropyl Ether, and Dibutyl Ether

The surface tension of diethyl ether, diisopropyl ether, and dibutyl ether were measured with a differential capillary rise method over the temperature range from (258 to 373) K, (248 to 373) K, and (263 to 373) K, respectively. The uncertainties of measurements for the temperature and surface tension were estimated to be within ± 10 mK and ± 0.2 mN·m−1. The results were correlated as a function of temperature, and the average absolute deviations were 0.053 mN·m−1 for diethyl ether, 0.041 mN·m−1 for diisopropyl ether, and 0.063 mN·m−1 for dibutyl ether, respectively.

Thermodynamic properties of HFO-1234yf (2,3,3,3-tetrafluoropropene)

Measurements of the thermodynamic properties of HFO-1234yf were conducted. The critical temperature T C, critical density ρ C, and critical pressure P C, were measured by the visual observation of the meniscus disappearance, and were determined to be 367.85 ± 0.01 K, 478 ± 3 kg/m 3, and 3382 ± 3 kPa, respectively. Vapor pressures were measured by a batch-type calorimeter with a metal-bellows in the temperature range from 310 K to 360 K and correlated by the Wagner-type equation. Surface tensions were measured by the differential capillary-rise method in the temperature range from 273 K to 340 K and correlated by the van der-Waals type equation. The acentric factor was determined to be 0.280 with the vapor pressure correlation. Based on the critical parameters and acentric factor, saturated vapor and liquid densities were estimated by the Peng–Robinson equation and the Hankinson–Thomson equation, respectively. The heat of vaporization was also calculated from the Clausius–Clapeyron equation.

Surface tension of pentafluoroethane + 1,1-difluoroethane from (243 to 328) K

The surface tension of the binary refrigerant mixture pentafluoroethane (HFC-125) + 1,1-difluoroethane (HFC-152a) was measured in the temperature range from (243 to 328) K with a differential capillary rise method, for three compositions around the composition of the optimum refrigeration performance (HFC-125 + HFC152a, 15%/85%). The uncertainties of the measurement of the temperature and the surface tension were estimated to be within ±10 mK and ±0.2 mN m −1, respectively. A correlation for the surface tension of the binary refrigerant mixture HFC-152a + HFC-125 was developed as a function of the composition.

Surface Tension of 2,2-Dimethylbutane from (233 to 378) K

The surface tension of 2,2-dimethylbutane was measured at temperatures from (233 to 378) K with a differential capillary rise method, together with the surface tension of heptane measured at temperatures from (303 to 358) K for verifying the experimental apparatus. The uncertainty of temperature is less than ± 10 mK. The uncertainty for surface tension was estimated to be within ± 0.2 mN·m−1. The surface tension results were correlated as a function of temperature with an average absolute deviation of 0.049 mN·m−1 for 2,2-dimethylbutane.

Measurements of the Surface Tension for the R290 + R32 Mixture

There were no data of the surface tension for the R290 + R32 mixture which is expected as one of the new refrigerant mixtures, and its prediction is considered to be difficult because it is a mixture of a very polar molecule with a nonpolar molecule. In this work, the surface tension measurements for the R290 + R32 mixture were carried out by the differential capillary-rise method modified for measuring mixtures. Thirty-one, thirty-five, and thirty-three data points were obtained with changing the composition of the mixture at T = 280 K, 290 K, and 300 K, respectively. The experimental uncertainties of temperature and surface tension are estimated to be within 20 mK and 0.2 mN·m−1, respectively. The excess molar surface tension is also calculated by the present data, and its uncertainty was estimated to be 0.3 mN·m−1. The excess molar surface tension was correlated as a function of composition. The deviation of the present data from the present correlation was within the experimental uncertainty.

Measurements of the surface tension for R290, R600a and R290/R600a mixture

The surface tensions of R290, R600a and R290/R600a mixture have been measured by the modified differential capillary-rise method. Twenty-two data points for R290 and 21 data points for R600a were obtained in the temperature range between 273 K and 354 K, and 43 data points for R290/R600a mixture on three isotherms of 278 K, 300 K and 320 K were obtained. The experimental uncertainties of temperature and surface tension are estimated to be within 20 mK and 0.2 mN m −1, respectively. Surface tension correlations as a function of temperature for pure R290 and R600a were formulated in the temperature range between 253 K and critical temperature, and the correlation as a function of the composition for R290/R600a mixture was discussed at 278 K, 300 K and 320 K. It is found that the surface tension for R290/R600a mixture can be reproduced by the simple mixing rule by mole fraction with the correlations of both pure components.