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[Obbectives] To study the optimal conditions for extracting procyanidins from Lycium ruthenicum Murr. with sub-critical fluid R134a (1,1,1,2-tetrafluoroethane) in 1 L extraction kettle. [Methods] Taking the extraction rate of procyanidins as an indicator, the influence of preesure, temperature, and extraction time on extraction rate of procyanidins from L. Ruthenicum Murr. was studied by single factor experimental methods and orthogonal array design. [Results] The order of factors affecting extraction rate of procyanidins was extraction temperature k extraction preesure k extraction time. The optimum extraction conditions were as follows % the extraction rate of procyanidins from L. ruthenicum Murr. was the highest with extraction preesure of 1.2 MPa, extraction temperature of 5 0 j and extraction time of 90 min. The content of procyanidins in L. ruthenicum Murr. from different producing areas was determined by vaniilin-HCl method under the optima conditions. [Conclusions] The method has the advantages of easy operation, good selectivity, low extraction temperature and high extraction efficiency, which is suitable for extraction of procyanidins in L. ruthenicum Murr. [ABSTRACT FROM AUTHOR]

The excess Gibbs free energy-equation of state ( G E EoS ) models is presented based on the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution method (PR-WS-MUNIFAC). The average absolute deviation (AAD) of vapor phase mass fraction and the absolute average relative deviation (AARD) of pressure are 0.0047 and 0.53%, respectively, for R152a + R1234yf; 0.0064、0.0050 and 1.59%, respectively, for R32 + R125 + R134a. The VLE properties of the ternary mixture R1234yf + R290 + R134a as a drop-in replacement for R134a were predicted over the temperature range of (253.15–313.15 K) at 10 K intervals. The vapor–liquid-liquid equilibrium (VLLE) was qualitatively analyzed in theory, and the relevant phase equilibrium diagrams were constructed. The R290 + R134a system has clear characteristics of VLLE near the azeotropic point; the pressure of the upper critical end point (UCEP) is approximately 1.627 MPa. Liquid phase separation also exists in the ternary system of R1234yf + R290 + R134a. [ABSTRACT FROM AUTHOR]

Abstract: The solubility of polystyrene with molecular weight of 100 000 and 260 000 g mol−1 was measured at temperatures from 313 to 333 K and at pressures from 5.0 to 13.0 MPa in subcritical 1,1,1,2‐tetrafluoroethane (R134a). The effects of pressure, temperature and molecular weight on the solubility of polystyrene were investigated. Meanwhile, the solubility of polystyrene was correlated using six density‐based semi‐empirical models (Chrastil, A‐L, K‐J, S‐S, M‐S‐T and Bartle). The M‐S‐T model was used to verify the self‐consistency of the experimental data, and the enthalpy values of polystyrene, including ΔHtotal, ΔHsub and ΔHsol, were estimated through the Chrastil and Bartle models. In addition, a modified M‐S‐T model was proposed through a detailed study of semi‐empirical model formulas and verified by the solubility of polystyrene in subcritical R134a and 38 other solid solutes in supercritical carbon dioxide and subcritical R134a. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, condensation heat transfer coefficients and frictional pressure drops of R-134a inside a micro-fin helical coiled tube with the cooling water flowing inside the shell in opposite flow direction are experimentally investigated. The inner tubes comprise of one smooth straight tube and one micro-fin helical coiled tube, which are made of copper. The experimental measurements are carried out at mass fluxes of 75, 115, 156 and 191 kg m −2  s −1 and saturation temperatures of 35° and 45 °C. In addition, the experimental data of a micro-fin helical coiled tube have been plotted on the mass flux versus vapor quality flow map and Tailtel and Dukler flow map. The transitions between different flow regimes inside micro-fin helical coiled tube have also been discussed. Moreover, the effect of mass flux, vapor quality and saturation temperature of R-134a on the heat transfer coefficients and pressure drops are examined. Comparisons between smooth straight tube and micro-fin helical coiled tube are also discussed. The experimental results show that the micro-fin helical coiled tube produces a higher heat transfer coefficient and a frictional pressure drop compared to smooth straight tube. The new correlations have been proposed to predict the Nusselt number and frictional pressure drop multiplier during condensation of R-134a inside micro-fin helical coil tube. [ABSTRACT FROM AUTHOR]

The falling film evaporation of R134a with nucleate boiling outside a triangular-pitch (2-3-2-3) tube bundle is experimentally investigated, and the effects of saturation temperature, film flow rate and heat flux on heat transfer performance are studied. To study the effect of cross vapor stream on the falling film evaporation, a novel test section is designed, including the tube bundle, liquid and extra vapor distributors. The measurements without extra vapor are conducted at the saturation temperature of 6, 10 and 16°C, film Reynolds number of 220 to 2650, and heat flux of 20 to 60 kWm−2. Cross vapor stream effect experiments are operated at three heat fluxes 20, 30, and 40 kWm−2 and two film flow rates of 0.035 and 0.07 kgm−1s−1, and the vapor velocity at the smallest clearance in the tube bundle varies from 0 to 2.4 ms−1. The results indicate that: film flow rate, heat flux and saturation temperature significantly influence the heat transfer; the cross vapor stream either promote or inhibit the falling film evaporation, depending on the tube position, film flow rate, heat flux and vapor velocity. [ABSTRACT FROM AUTHOR]

The solubility of o -aminobenzamide ( o -AB) and its mixture with o -nitrobenzoic acid ( o -NBA) in subcritical 1,1,1,2-tetrafluoroethane (R134a) was measured at temperatures of 308, 318, 328 K and pressure range from 5.0 to 15.0 MPa with static method. Then the solubility of o -AB and o -NBA in subcritical R134a binary and ternary system were compared and investigated from the view of solvent density, solvent polarity, and interaction between solvent and solute. In order to evaluate the effect of co-solute on solubility of solute, enhancement factor ( EF ), separation factor ( SF ), separation efficiency ( SE ), and the solubility enhancement coefficient ( α ) were defined and calculated. In addition, empirical models, including Chrastil, A–L, K–J, S–S, and M–T models applying for binary system, with González, Sovová, M–M–T, and Z–J models applying for ternary system, are used for correlating the experimental solubility. The satisfactory correlated results were obtained with the AARD range from 2.16% to 4.75%. [ABSTRACT FROM AUTHOR]

The paper presents experimental and theoretical studies of wavy flows during R134a condensation in oval parallel microchannels with a hydraulic diameter of 301.6 µm for mass fluxes from 60 to 250 kg/(m 2 s) and vapor mass qualities from 0.1 to 0.9. The inlet saturation temperature of R134a is 31.3°C. Waves were seen in the thin liquid film and in the channel corners with measurements of their wave lengths and velocities. The results show that both the film wave length and the corner wave length increase with decreasing mass flux and decreasing vapor mass quality. Additionally, the film wave velocity and corner wave velocity both increase with increasing mass flux. The cooling method, either asymmetric cooling or symmetric cooling, only affected the corner wave length and velocity along the channel except near the inlet. A two-dimensional theoretical model was developed to predict the liquid-vapor interface instability conditions during condensation flow by neglecting the liquid inertia and vapor flow viscous terms. The normal modes method was used to analyze the system instability reactions to various perturbation wave lengths. Two modes were obtained with one giving the greatest instability wave length which agrees well with the measured wave length data. [ABSTRACT FROM AUTHOR]

An experimental study with a horizontal 1.002 mm inner diameter mini-tube is conducted to investigate the two-phase frictional pressure drop of R134a flow boiling under hypergravity. Totally 1718 data points under the gravity from 1 to 3.16 g were obtained, with mass fluxes of 400–1075 kg/m 2  s, vapor qualities of 0.05–0.85, heat fluxes of 24.0 and 31.5 kW/m 2 , and saturation pressures of 0.6 and 0.7 MPa. The hypergravity conditions were achieved using a centrifugal acceleration machine. The results show that with increasing gravity the flow boiling frictional pressure drop increases at high vapor quality but decreases at low vapor quality, and the trend reversals take place roughly in the range of 0.07 <  x  < 0.45, depending on saturation pressure and mass flux. The comparison between the experimental data and the predictions of 28 correlations of two-phase frictional pressure drop is made, and the results show that the best correlation has a mean absolute deviation of 12.8% for the entire data, 10.6% for normal gravity, and 13.7% for hypergravity. [ABSTRACT FROM AUTHOR]

An investigation into the effect of mass flow rate oscillation on the R-134a evaporation heat transportation in a horizontal annular duct was experimentally conducted. The experiments were performed at different amplitudes (10, 20, and 30%) and periods (20, 30, 60, and 120 s) of the mass flux oscillation in a duct with different gap sizes (1.0, 2.0 and 5.0 mm). In this regard, the time variations of evaporation heat transportation coefficient and the heated wall temperature were also analyzed for the thermal characteristics of the oscillatory evaporation heat transfer. Measured results showed that the amplitude and period of the mass flux oscillation insignificantly affected the time-average heat transportation coefficient for the R-134a oscillatory evaporation heat transfer. However, the larger amplitudes and longer periods of the mass flux oscillation led to stronger wall temperature oscillations. [ABSTRACT FROM AUTHOR]

2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)) have gained increasing interesting due to their environmental properties and are expected as alternatives to 1,1,1,2-tetrafluoroethane (R134a). The purpose of this work is to investigate the thermal diffusivities of the two refrigerants with dynamic light scattering method, for which the reliability of the experimental setup was checked at first by measuring the thermal diffusivity of R134a. Then the thermal diffusivities of R1234yf and R1234ze(E) in the liquid phase were measured under saturation conditions from 298 K up to 378 K. The relative combined uncertainties of thermal diffusivity were estimated to be 2%, and increased to 3% when the reduced temperature above 0.95. [ABSTRACT FROM AUTHOR]