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Freshwater scarcity is a critical issue in Vietnam, particularly in the Mekong Delta, a densely populated region with an agriculture-based economy. This scarcity is largely driven by saltwater intrusion during the dry season, severely affecting both agriculture and the local economy. In response, advanced desalination technologies have been proposed. In this study, we investigated the use of cyclopentane (CP), a liquid guest molecule, and 1,1,1,2-tetrafluoroethane (R134a), a gaseous guest molecule, as hydrate formers to desalinate saline water from the Mekong Delta. This study aimed to evaluate and compare the freshwater recovery efficiencies of these hydrate formers and assess the potential of hydrate technology for practical application in the region. We performed thermodynamic and kinetic investigations on sodium chloride solutions (1.0-3.5 wt%), representing the salinity levels of seawater in the Mekong Delta, to establish a laboratory-scale desalination system. The results showed a consistent thermodynamic trend: the higher concentration of samples leads to the longer time of hydrate formation to achieve the conversion of water into hydrates exceeding 60 %. Additionally, the CP and R134a hydrate structures were characterized using Raman spectroscopy, which revealed significant changes in the water peak and C-H band signal during the hydrate formation process. After a single-stage hydrate treatment using CP and R134a, the removal efficiencies for ions and total dissolved solids in saline water samples from the Mekong Delta exceeded 75 % and 70 %, respectively. These findings serve as a reference for developing a larger-scale hydrate-based desalination technology to address the challenges of saltwater intrusion in the Mekong Delta region., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

We present a new wide-ranging correlation for the viscosity of 1,1,1,2-tetrafluoroethane (R-134a) based on critically evaluated experimental data. The correlation is designed to be used with densities from an existing equation of state, which is valid from the triple point to 438 K, at pressures up to 70 MPa. The estimated uncertainty (at the 95 % confidence level) for the viscosity varies depending on the temperature and pressure, from a low of 0.2 % in the dilute-gas range near room temperature, to 2 % along the saturated vapor boundary, 2.5 % for the saturated liquid, and 4 % for some high-pressure regions. The correlation behaves in a physically reasonable manner when extrapolated to pressures above 70 MPa. Comparisons with experimental data at pressures to 400 MPa are given. However, care should be taken when using the correlation outside of the validated range of the equation of state. [ABSTRACT FROM AUTHOR]

Pyrolysis is one of the potential way for the degradation of hydrofluorocarbons, but it is difficult to make effective use of the complex pyrolysis products. The addition of plastics can provide sufficient hydrogen source for the degradation of hydrofluorocarbons to generate the high value-added chemicals and fuels. Density functional theory calculation and reactive molecular dynamic simulation are employed to investigate the co-pyrolysis mechanism of 1,1,1,2-tetrafluoroethane and low-density polyethylene in this work. The results show that the H atoms provided by low-density polyethylene promote the defluorination reactions of 1,1,1,2-tetrafluoroethane to generate HF and short chain hydrocarbons, and the number of F atoms in HF molecules accounted for nearly 80 % of the whole reaction system, achieving a better defluorination effect. The defluorination rate of 1,1,1,2-tetrafluoroethane and plastics co-pyrolysis is more than 5 times that of pure 1,1,1,2-tetrafluoroethane pyrolysis. The main co-pyrolysis products of 1,1,1,2-tetrafluoroethane and low-density polyethylene are H 2 , HF and short chain hydrocarbons, the purpose of hydrofluorocarbons degradation into high value-added chemicals and fuels is realized in this study. This work provides a green, effective way for the conversion waste hydrofluorocarbons and waste plastics into high value-added chemicals and fuels, and achieves the conversion of waste hydrofluorocarbon refrigerants to more economical products. • Co-pyrolysis mechanism of hydrofluorocarbons and plastic is first time studied. • Co-pyrolysis process of 1,1,1,2-tetrafluoroethane and low-density polyethylene is described. • Plastic as a hydrogen donor promotes the defluorination of 1,1,1,2-tetrafluoroethane. • HF, H 2 and short chain hydrocarbons rich products could be selectively obtained. • Pyrolysis products of waste hydrofluorocarbons can be enhanced by adding plastics. [ABSTRACT FROM AUTHOR]

In this study, we have examined the modeling of gas solubility in twenty room temperature ionic liquids based on the van der Waals and generic Redlich–Kwong equations of state and have also compared the obtained deviations with each other. The selected gases are carbon dioxide (R744) and 1,1,1,2-tetrafluoroethane (R134a). Experimental data represent a high correlation with the present equations of state. It is concluded that the absolute average deviation is less than 1% for each system, which illustrates the high accuracy and efficiency of the mentioned equations of state. Henry's law constant and some thermodynamic properties such as enthalpy and entropy in infinite dilution are calculated. [ABSTRACT FROM AUTHOR]

A convenient synthesis of chiral N -nitro-oxazolidin-2-ones by nitration of α-amino acid derived 1,3-oxazolidin-2-ones containing one or two stereogenic centers with dinitrogen pentoxide in liquefied 1,1,1,2-tetrafluoroethane medium has been developed. The obtained N -nitroheterocycles were converted into enantiomerically pure O -(β-nitraminoalkyl) carbamates by treatment with ammonia or amines in the same solvent. The synthesized N -nitro compounds are slightly toxic in vitro to Human Embryonic Kidney 293 (HEK293) cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The strong interactions between R-1234yf and R-134a in R-513A were between C atoms (-CF 3 groups). • The vdW interaction of refrigerant-anion was proportional to the solubility of R-134a/R-1234yf in nitrile-based ILs. • Nonbonding interactions vary between R-134a-anion and R-1234yf-anion, impacting nitrile-based IL selectivity. • R-134a and R-1234yf had strong interactions with the N atoms in the anions of nitrile-based ILs. The reclamation of mixed refrigerants stands as a potent measure to substantially mitigate the emission of fluorinated gases (F-gases). In the separation of the azeotropic refrigerant R-513A (comprising 56 wt% R-1234yf, 2,3,3,3-Tetrafluoropropene, and 44 wt% R-134a, 1,1,1,2-Tetrafluoroethane), the extractive distillation process using ionic liquids (ILs) was employed. The molecular structure of nitrile-based ILs ([C 4 C 1 im][SCN], [C 4 C 1 im][N(CN) 2 ], [C 4 C 1 im][C(CN) 3 ], [C 4 C 1 im][B(CN) 4 ]) exerts a regular impact on the solubility of refrigerants, thereby necessitating molecular dynamics simulation to ascertain the law of refrigerant solubility in ILs concurrent with the augmentation in the number of –CN in the anion. Additionally, an analysis was conducted to elucidate the mechanism underlying the high selectivity of nitrile-based ILs. The results revealed pronounced interactions between R-1234yf and R-134a, predominantly occurring between carbon atoms (-CF 3 groups in R-134a and R-1234yf), and chiefly van der Waals interactions. An enhancement in the number of –CN in anion led to the fortification of the van der Waals interaction between R-134a/R-1234yf and the anion. The stronger nonbonding interaction energy between R-134a and the anion, as well as the higher radial distribution function (RDF) peak height between R-134a and the anion, signified a more robust interaction between R-134a and the anion compared to R-1234yf and the anion. Concurrently, the variance in the RDFs in the anion-C atom (-CH 2 F group in R-134a and -CF group in R-1234yf) revealed the selectivity of the four ILs to R-134a and R-1234yf. Among the four anions, [B(CN) 4 ]− exhibited the most interaction sites with R-134a. This investigation contributes significantly to comprehending the interaction mechanism of azeotropic refrigerants and the interaction mechanism between refrigerants and nitrile-based ILs. [ABSTRACT FROM AUTHOR]

The reaction of 1,1,1,2-tetrafluoroethane with fluorine in a gas-liquid reactor with a high-speed stirrer and with perfluorodecalin or perfluoro-1,3-dimethylcyclohexane as a liquid phase occurs as hydrogen substitution without noticeable cleavage of C-C bonds, yielding penta- and hexafluoroethane. The fluorination of methane in perfluorodecalin under the same conditions yields, depending on the methane and fluorine concentrations in their mixtures with an inert gas, products of successive hydrogen substitution by fluorine when the reaction occurs in approximately isothermal mode and products corresponding to the thermodynamic equilibrium when the reaction occurs in the mode of gas-phase diffusion combustion on the gas bubble scale. [ABSTRACT FROM AUTHOR]

In this study, heat transfer coefficients and pressure drops of R-134a inside round and flat tubes are investigated experimentally with mass flux of 450, 550, and 650 kg m−2 s−1 at saturation temperatures of 35°, 40°, and 45°C. The effects of mass flux and saturation temperature on heat transfer coefficient and pressure drop are examined. The maximum enhancement factor and pressure drop penalty are obtained by flat tube (FT-2) up to 2.101 at 450 kg m−2 s−1 and 3.01 at 650 kg m−2 s−1, respectively. The correlation for flat tubes is proposed to predict the heat transfer coefficient within ±20% error. [ABSTRACT FROM AUTHOR]

Heat transfer and pressure drop characteristics of R-134a boiling in a chevron-patterned brazed plate heat exchanger (BPHE) are studied experimentally. With corrugated BPHE channels having hydraulic diameter of 3.4 mm and low refrigerant mass flux, boiling near the micro-macroscale transition is speculated. Heat exchanger performance is characterized with varying mass flux (30-50 kgm-2s-1), saturation pressure (675 kPa and 833 kPa), heat flux (0.8 and 2.5 kWm-2), and vapor quality (0.1-0.9). The two-phase refrigerant heat transfer coefficient increases with heat flux as often observed during nucleate boiling. It also weakly increases with saturation pressure and the associated lower latent heat during convective boiling; heat transfer is improved by the decreased liquid film thickness surrounding confined bubbles inside the narrow BPHE channels, which is the main characteristic of microscale boiling. As often observed in macroscale boiling, the inertial forces of the liquid and vapor phases cause an unsteady annular film, leading to premature partial dryout. The onset of dryout is accelerated at the lower saturation pressure, due to increased surface tension, another microscale-like characteristic. Higher surface tension retains liquid in sharp corners of the corrugated channel, leaving lateral surface areas of the wall dry. Two-phase pressure drop increases with mass flux and vapor quality, but with decreasing saturation pressure. Dryout decreases the friction factor due to the much lower viscosity of the gas phase in contact with the wall. Several semi-empirical transition criteria and correlations buttress the current analyses that the thermal-fluidic characteristics peculiar to BPHEs might be due to macro-microscale transition in boiling. [ABSTRACT FROM AUTHOR]

In this work, the condensation of refrigerants on a single, high-density, low-fin tube and full-sized shell and tube condensers were investigated experimentally. The low-fin tube had an external fin density of 56 fins per inch (fpi) and fin height 1.023mm. Another three-dimensional (3D) finned tube was also tested for comparison. The condensing heat transfer coefficient of the refrigerant R134a was first investigated outside a single horizontal tube at saturation temperature of 40°C. The overall heat transfer coefficients of the two tubes were similar in magnitude. The condensing heat transfer coefficient of the low-fin tube was 16.3-25.2% higher than that of 3D enhanced tube. The experiments of the two condensers mounted with low-fin and 3D enhanced tubes were then conducted in centrifugal and screw chiller test rigs. It was found that chillers with the two different condensers generally had the same refrigeration capacity under the same experiment conditions. The refrigeration capacity of the screw chiller was smaller. It had fewer tube rows and elicited fewer inundation effects owing to the falling condensate. The heat transfer coefficients of the condensers with R134a in centrifugal chillers equipped with high-density low-finned tubes were higher than those in the screw chillers. The total number of tubes for low-fin tube condensers, in the two chillers, was reduced by approximately 15% compared with the use of domestic advanced condensers equipped with the 3D enhanced tubes. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of an adiabatic flow of R-134a through a capillary tube. The paper discusses the details of experimental facility for testing a capillary tube with sub-cooled and two phase inlet conditions of R-134a. The effect of diameter, capillary length, inlet refrigerant quality and inlet pressure on mass flow rate were investigated. The experiments for testing the capillary tubes were proceeded by an integrity test. The vapour quality varied from 0.05 to 0.25. All the experiments were done by varying the pressure from 655 to 724 kPa. The effect of two phase inlet conditions on mass flow rate of R-134a through an adiabatic capillary tube is observed. A correlation to predict the mass flow rate of refrigerant flowing through an adiabatic capillary tube is proposed for two phase inlet conditions. The proposed correlation predicts the measured data with an error band of ±25%. [ABSTRACT FROM AUTHOR]

A nano-composite from biologically obtained chitin nanofillers homogenously dispersed in a poly( ε -caprolactone) matrix was successfully achieved by an ultrasonication-assisted non-toxic and non-aqueous methodology. For this purpose, biological chitin was obtained from lactic acid fermentation of shrimp wastes and converted into chitin whiskers by acidic hydrolysis in a novel process at low temperature (4 °C) that enhanced the distribution and yield. Additionally, the polyester matrix was enzymatically produced in a non-toxic compressed fluid (1,1,1,2-tetrafluoroethane at 25 bar and 65 °C) medium. The homogeneous distribution of the nanofiller in the matrix was corroborated by confocal and atomic force microscopies. Films of the nanocomposite were physicochemically characterized to assess its adequate properties. Additionally, the qualitative viability of human fibroblasts and osteoblasts cells was studied on the produced nanocomposite films showing good biocompatibility. [ABSTRACT FROM AUTHOR]

This work presents the experimental evaluation of energy consumption and refrigerant charge reduction when a commercial direct expansion refrigeration system is converted into an indirect system. The evaluation (with R-134a and R-507A) used a commercial cabinet with doors for medium temperature and a single-stage refrigeration cycle using a semi-hermetic compressor and electronic expansion valve; 24-h energy consumption tests were performed at laboratory conditions for each refrigerant and configuration at three heat rejection levels (23.3, 32.8 and 43.6 °C), maintaining an average product temperature inside the cabinet of 2 °C. The work analyses the impact of the conversion on temperature and pressure indicators, as well as, in the energy performance of each element. For R-134a the refrigerant charge was reduced in a 42.9%, but the energy consumption rose by 22.0%-22.8%; for R-507A the charge reduction was of 32.8% with an increase in energy consumption of between 27.7% and 38.7%. [ABSTRACT FROM AUTHOR]

Rutin is a common dietary flavonoid that has been widely consumed in pharmaceutical industry. To facilitate the extraction of rutin from plant tissues, we determined the solubility of rutin in supercritical carbon dioxide by dynamic method at 313.2–343.2 K over the pressures range of 9.0–18.0 MPa and in subcritical 1,1,1,2-tetrafluoroethane (R134a) by static method at 313.2–343.2 K over the pressures rang of 7.0–18.0 MPa. The experimental results indicate that the extraction of rutin should be operated by subcritical R134a or supercritical CO 2 below or above the transition pressure (the pressure at which the rutin solubilities in subcritical R134a and supercritical CO 2 are the same), respectively. Furthermore, the solubility data were satisfactorily correlated by Chrastil model and m-ER&HV model (modified Esmaeilzadeh–Roshanfekr equation of state combined with Huron–Vidal mixing rule), and the thermodynamic consistency of the solubility data was confirmed by the thermodynamic consistency test. [ABSTRACT FROM AUTHOR]

The condensation heat transfer coefficient of R134a was experimentally studied inside two smooth and four micro-fin tubes. The working conditions and structural parameters of the test tubes were selected as the influencing factors, and the experiment was conducted under mass velocities of 400-1100 kg.m-2.s-1, condensation temperatures of 35-45 °C and water-testing Reynolds numbers of 8000-22,000, with an inlet superheat of 1-2 °C and outlet subcooling of 1-2 °C at the test section for the refrigerant. Experimental results indicate that the heat transfer coefficient increases with increasing mass velocity and decreasing condensation temperature and water-testing Reynolds number. The heat transfer coefficient of the micro-fin tube with a helix angle of 28° is the highest and that of smooth tube is the lowest for test tubes with the same inner diameter. Tube diameter has a small influence on the heat transfer coefficient for the smooth tubes while the heat transfer coefficient increases with decreasing tube diameter for the micro-fin tubes. The heat transfer coefficient inside the test tube was compared with some well-known existing correlations, and results show that correlations by Cavallini et al., Thome et al., Shah and Akers et al. can estimate the experimental data with mean absolute deviation of less than 30%, and correlations of Dobson and Chato et al. and Jung et al. cannot be used to capture the heat transfer coefficient with mean absolute deviations of 140.18% and 146.23%, respectively. While the Miyara et al. correlation overestimates the heat transfer coefficient, correlations of Cavallini et al., Koyama et al. and Oliver et al. all underestimate the experimental data for the micro-fin tube. Their deviations are from 25 to 55% for micro-fin tubes 3 and 4, while their deviations keep to within 30% for micro-fin tubes 5 and 6. Finally, to improve the correlation prediction accuracy, a dimensionless parameter was introduced to the correlations of Dobson and Chato et al. and Jung et al., and correlations of Cavallini et al., Koyama et al. and Oliver et al. were modified by enhancing the turbulence effect. The prediction accuracy of all modified correlations can be controlled to within 30%. [ABSTRACT FROM AUTHOR]

Nano α-aluminum fluorides with high surface area were synthesized by a simple ethylene glycol mediated sol–gel technique using dilute aq. HF as the F source, and their performances were investigated for gas-phase dehydrofluorination of 1,1,1,2-tetrafluoroethane at relatively low reaction temperature (400 °C). Aluminum precursor was crucial for the phase composition, textural and acidic properties of the resulting fluoride. Commercially low-cost and available inorganic Al was firstly used as precursor for synthesis of aluminum fluorides via the sol–gel route, and the as-prepared α-AlF 3 possessed high surface area (up to 170 m 2 g −1 ) and strong surface acidities even after thermal treatment of 400 °C. The presence of sulfate ions suppressed the crystallization of aluminum fluoride during calcination when Al 2 (SO 4 ) 3 was used as precursor, leading to an amorphous phase for as-prepared AlF 3 . Aluminum fluorides with β and pyrochlore phase were prepared using aluminum isopropoxide and aluminum diacetate hydroxide, respectively, as precursors. Based on the results of IR, XRD and element analysis, it is concluded that the formation of Al-glycolates during the sol–gel process can effectively reduce the hydrolysis of precursor and suppress particle agglomeration, thus leading to dominant formation of nano aluminum fluorides. The residual O derived from minor hydrolysis can resist sintering under high-temperature treatment, which is a key factor to improve the thermostability of as-prepared aluminum fluoride. Due to their large Lewis acidic amounts, the α-AlF 3 derived from AlOOH and Al 2 O 3 exhibited remarkably high catalytic activity with CF 3 CH 2 F conversion of 24%–28% and CF 2 =CHF selectivity above 98%, which were far higher than that of AlF 3 prepared by traditional methods. [ABSTRACT FROM AUTHOR]

• Ethylene Response Factor 1 (ERF1) plays a crucial role in biotic and abiotic stress responses. Previous studies have shown that ERF1 regulates stress-responsive gene expression by binding to different cis-acting elements in response to various stress signals. ERF1 was also reported to be unstable in the dark, and it regulates hypocotyl elongation. Here, we elucidated the mechanism underlying degradation of ERF1. • Yeast two-hybrid screening showed that UBIQUITIN-CONJUGATING ENZYME 18 (UBC18) interacted with ERF1. The interaction between ERF1 and UBC18 was verified using pull-down assays and coimmunoprecipitation analyses. We then compared the ERF1 protein abundance in the UBC18 mutant and overexpression plants. Based on the results of protein degradation and in vivo ubiquitination assays, we proposed that UBC18 mediates ERF1 ubiquitination and degradation. • ERF1 was more stable in UBC18 mutants and less stable in UBC18 overexpression lines compared with that in wild-type plants. ERF1 was degraded by the 26S proteasome system via regulation of UBC18 and promotes dark-repression of downstream genes and proline accumulation. • UBC18 negatively regulated drought and salt stress responses by altering the abundance of ERF1 and the expression of genes downstream of ERF1. [ABSTRACT FROM AUTHOR]

In this study the transfer coefficient of evaporation heat of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger was experimentally investigated. The results are presented as the dependancy of the mean heat transfer coefficient for the whole heat exchanger on the mean vapor quality. The influences of mass flux, heat flux and flow configuration on the heat transfer coefficient were also taken into account and a comparison with previously published experimental data and literature correlations was made. .

Experimental results for the pressure drop during the evaporation of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger are presented in this paper. The influences of mass flux, heat flux and vapor quality on the two-phase pressure drop are specially analyzed and compared with previously published experimental data and literature correlations. All results are given in graphical form as the dependency of the frictional pressure drop on the mean vapor quality. .

This paper presents the comparative analysis of HFO1234ze(E) and HFC134a during vaporisation inside a 4 mm smooth tube. The experimental tests were carried out at three different saturation temperatures (10, 15, and 20 °C) at increasing vapour quality up to incipient dryout to evaluate the specific contribution of heat flux, refrigerant mass flux, mean vapour quality, and saturation temperature (pressure). The heat transfer coefficients have a positive slope versus vapour quality and the slope increases with refrigerant mass flux and decreases with heat flux. Saturation temperature (pressure), refrigerant mass flux and mean vapour quality have a remarkable impact on the frictional pressure drop of both HFO1234ze(E) and HFC134a whereas the effect of heat flux appears marginal or negligible. Convective boiling seems to be the prevailing heat transfer regime in the present experimental tests. HFO1234ze(E) exhibits heat transfer coefficients similar to HFC134a and slightly higher frictional pressure drops. [ABSTRACT FROM AUTHOR]

Supermarket chains require benchmarking and analysing refrigeration performance in order to manage their energy efficiency investments. This paper contributes in robustly assessing refrigeration system energy and carbon performance in which commonly believed drivers are used to conduct correlations. Based on this, refrigeration connected load, store opening hours and external temperature were found to construct a more representative energy performance indicator (EPI) than other metrics. By using such an indicator, it is possible to identify poor performing systems from an estate portfolio and thus select sites suitable for energy saving measures. Furthermore, energy impact from introducing natural refrigerants is examined using empirical data from a UK supermarket chain. It was found that CO 2 systems have different seasonal performance than HFC systems, nonetheless on an annual basis no system has a clear edge over another. Lastly, other initiatives such as cabinet night blinds and suction pressure optimisation achieved 10% and 7% energy reduction respectively. [ABSTRACT FROM AUTHOR]

Inhaled corticosteroids (ICS) and β2-agonists are the primary pharmacotherapies of asthma management. However, suboptimal medication compliance is common in asthmatics and is associated with increased morbidity. We hypothesized that exhaled breath measurements of the aerosol used in the inhaled medications might prove useful as surrogate marker for asthma medication compliance. To explore this, 10 healthy controls were recruited and randomly assigned to ICS (Flovent HFA) or short acting bronchodilators (Proventil HFA). Both inhalers contain HFA-134a as aerosol propellant. Exhaled breath sampling and pulmonary function tests were performed prior to the inhaler medication dispersion, immediately after inhalation, then at 2, 4, 6, 8, 24, and 48 hours postadministration. At baseline, mean (SD) levels of HFA-134a in the breath were 252 (156) pptv. Immediately after inhalation, HFA-134a breath levels increased to 300 × 106 pptv and were still well above ambient levels 24 hours postadministration. The calculated ratio of forced expiratory volume in 1 second over forced vital capacity did not change over time following inhaler administration. This study demonstrates, for the first time, that breath HFA-134a levels can be used to assess inhaler medication compliance. It may also be used to evaluate how effectively the medicine is delivered. [ABSTRACT FROM AUTHOR]

In this work, the use of homogenous media composed of the ionic liquid [C4MIM] [PF6] in combination with miscible compressed 1,1,1,2-tetrafluoroethane (R134a), above the critical points of the mixture, at 338.15 and 363.15 K and pressure of 30,000 kPa, lead to the successful enzyme-mediated syntheses of linear and hyperbranched poly- l -lactides. The attained polymer molecular weights were higher than those in previous reports using compressed fluids, even in the supercritical state, or individual ionic liquid media. The maximum attained M n for linear PLLA in this work was 28,000 g/mol, and that for hyperbranched was 11,200 g/mol which were up to 3-fold higher than those obtained with the ionic liquid medium, and this is attributed to favored reaction media characteristics in this critical/miscible system. Additionally, non-enzymatic propagation side mechanisms were minimized or eliminated with the addition of the green compressed R134a. [ABSTRACT FROM AUTHOR]

A low temperature (176 K), high resolution far-IR spectrum of 1,1,1,2-tetrafluoroethane (HFC-134a) has been recorded at the Australian Synchrotron Far-IR beamline. The ν 8 band, located at 665.62 cm −1 , has been analysed and 4635 ro-vibrational transitions were assigned and confirmed using ground state combination differences. Local perturbations emanating from two interacting dark states were identified, and subsequently treated using two c -axis Coriolis coupling terms. The necessary modifications of a collisional cooling/enclosive flow cooling cell for synchrotron far-IR spectroscopy are outlined. [ABSTRACT FROM AUTHOR]

The porous alumina catalysts with different acidity were prepared and tested for dehydrofluorination of 1,1,1,2-tetrafluoroethane to synthesize trifluoroethylene. The XRD, BET, SEM, NH-TPD and py-IR techniques were used to characterize the alumina catalysts with different calcination temperatures. The porous θ-AlO showed the excellent catalytic performance, with 35.1 % conversion and the selectivity to trifluoroethylene of 99.0 %. The active sites of catalysts for formation of trifluoroethylene are appropriate weak Lewis acid sites, and the strong Lewis acid sites may result in its rapid deactivation, due to the coke or polymerization of trifluoroethylene. Graphical Abstract: Dehydrofluorination of 1,1,1,2-tetrafluoroethane (CFCFH) is a promising route to synthesize trifluoroethylene over θ-AlO, the conversion is 35.1 % and the selectivity to trifluoroethylene is 99 % at 450 °C. It was suggested that appropriate number of weak Lewis acid sites was beneficial to the catalysis for dehydrofluorination of CFCFH, the weak Lewis acid sites as the active sites of synthesis of trifluoroethylene. On the other hand, the strong Lewis acid sites easily result in deactivation of catalysts derived from the coke or polymerization of trifluoroethylene.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The performance of 1,1,1,2-tetrafluoroethane or HFC-134a decomposition and the formation of byproducts in a dielectric barrier discharge plasma reactor were studied with different packing systems such as α-AlO (porous and nonporous), γ-AlO (porous) and ZrO (nonporous). Experimental variables such as reactor temperature, initial HFC-134a concentration and oxygen levels were chosen for the performance analysis. Among the packing systems, the porous γ-AlO and α-AlO decomposed HFC-134a much more effectively than the nonporous α-AlO and ZrO. The combination of the plasma with the porous γ-AlO was found to cover a wide range of initial concentration. The decomposition efficiency tended to increase with the addition of oxygen up to 2 %, but further increase in the oxygen led to a decrease. As well as carbon oxides (CO and CO), significant amounts of unwanted byproducts such as COF and CF were also identified in the effluent gas with the nonporous α-AlO and ZrO. On the contrary, with the porous γ-AlO and α-AlO, such unwanted byproducts were considerably suppressed, enhancing the formation of CO and CO. [ABSTRACT FROM AUTHOR]

High-resolution infrared absorption cross sections for 1,1,1,2-tetrafluoroethane have been determined over the spectral range 750–1600 cm −1 from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra of 1,1,1,2-tetrafluoroethane/dry synthetic air mixtures were recorded at 0.015 cm −1 resolution (calculated as 0.9/MOPD) at a number of temperatures and pressures (22–761 Torr and 191–296 K) appropriate for atmospheric conditions. Intensities were calibrated using composite 1,1,1,2-tetrafluoroethane spectra taken from the Pacific Northwest National Laboratory (PNNL) IR database. This cross section dataset is intended to replace what is currently available in the HITRAN/GEISA databases. [ABSTRACT FROM AUTHOR]

Many vehicle owners in the United States recharge their vehicles' air conditioning systems with small containers of hydrofluorocarbon-134a (HFC-134a, CH 2 FCF 3 ), at a frequency estimated to be once every year on average. Such nonprofessional service produces immediate emissions of this potent greenhouse gas during service and from the residual heel in partially used containers. The nonprofessional operations are also associated with increased delayed refrigerant emissions that occur because owners are less likely to repair leaks than professional technicians. In California, an estimated 1.3 million nonprofessional service operations performed each year generate 0.27 ± 0.07 million metric ton CO 2 equivalent (MMTCO 2 e) of immediate emissions and 0.54 ± 0.08 MMTCO 2 e of delayed emissions, using a Global Warming Potential of 1300 for HFC-134a. The immediate emissions can be largely mitigated by a regulation that requires self-sealing valves and improved labeling instructions on the containers, a deposit-return-recycling program for the containers, and a consumer education program. If 95% of the used containers were to be returned by consumers for recycling of the container heel, the annual immediate emissions would be reduced by 0.26 ± 0.07 MMTCO 2 e. In the United States, an estimated 24 million nonprofessional service operations are performed each year, generating 5.1 ± 1.4 MMTCO 2 e of immediate emissions and 10.4 ± 1.5 MMTCO 2 e of delayed emissions. Mitigation measures equivalent to the California regulation would reduce nationwide immediate emissions by 4.9 ± 1.4 MMTCO 2 e, if 95% of the used cans were returned for recycling. These business-as-usual emissions and mitigation potentials are projected to stay approximately constant until around 2022, and remain at significant levels into the 2030s. [ABSTRACT FROM AUTHOR]

The fluorocarbon films were synthesized by radio frequency pulsed 1, 1, 1, 2-tetrafluoroethane plasma polymerization using various duty cycles. The deposition rates and water contact angles were examined for radio frequency pulsed plasma polymerized fluorocarbon films. The film surface properties were also determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. For varying duty cycle from 100% to 10% in pulsed plasma process, the plasma polymerized film drastically changed the surface property. Specifically, it has been observed that modulated plasmas with the proper duty cycle of 10% lead to the formation of the super-hydrophobic film by static water contact angle value of 150°. The surface properties of fluorocarbon films were determined as the Cassie state. In the transmittance, UV–VIS transmission spectra showed that these radio frequency pulsed plasma polymerized coatings were transparent in visible light region. By adjusting duty cycles in relation to radio frequency pulsed plasma polymerization, the hydrophobicity of the resulting thin fluorocarbon films could be tuned. [ABSTRACT FROM AUTHOR]

Abstract: R-134a (C2H2F4) is a low cost, easily available and chlorine free refrigerant, which in its superheated state can be used as an efficient neutron detector. Due to its high solubility in water the R-134a based superheated droplet detectors (SDD) are usually very unstable unless the detector is fabricated using a suitable additive, which stabilizes the detector. The SDD is known to have superheated droplets distributed in a short-lived and in a relatively long-lived metastable states. We have studied the detector response to neutrons using a 241AmBe neutron source and obtained the temperature variation of the nucleation parameters and the interstate kinetics of these droplets using a two-state model. [Copyright &y& Elsevier]

In this study, experimental and simulation studies of the evaporation heat transfer coefficient and pressure drop of R-134a flowing through corrugated tubes are conducted. The test section is a horizontal counter-flow concentric tube-in-tube heat exchanger 2.0 m in length. A smooth tube and corrugated tubes with inner diameters of 8.7 mm are used as the inner tube. The outer tube is made from a smooth copper tube with an inner diameter of 21.2 mm. The corrugation pitches used in this study are 5.08, 6.35, and 8.46 mm. Similarly, the corrugation depths are 1, 1.25, and 1.5 mm, respectively. The results show that the maximum heat transfer coefficient and pressure drop obtained from the corrugated tube are up to 22 and 19 % higher than those obtained from the smooth tube, respectively. In addition, the average difference of the heat transfer coefficient and pressure drop between the simulation model and experimental data are about 10 and 15 %, respectively. [ABSTRACT FROM AUTHOR]