Hydrofluorocarbon 134a Research Articles

Making insulation more climate friendly

Insulating and air sealing are effective ways to reduce the carbon footprints of homes and other buildings, and rigid foam panels are a popular material for doing that work. But many of the panels have a little-known climate cost: the global warming potential (GWP) of the gas, or blowing agent, used to puff the foam. In the case of panels made of extruded polystyrene (XPS)—a closed-cell foam suitable for wet or dry conditions—that gas has been hydrofluorocarbon-134a (HFC-134a). HFC-134a is a good blowing agent , but it has a GWP of 1,430, meaning it traps 1,430 times as much heat as carbon dioxide does over 100 years. As regulations seeking to eliminate HFC-134a take effect this year in Canada and the US, panel makers including Owens Corning and DuPont are switching their blowing agents to blends containing hydrofluoroolefins (HFOs). Refrigeration is the largest use for HFCs and other fluorocarbon gases,

Removal of HFC-134a from Brackish Water Using a Semi Batch Jet Loop Reactor

Mineral salt components (Na+, Ca2+, K+, Mg2+, etc.) are naturally excluded during the gas hydrate in which water molecules form cavities by hydrogen bonding and guest gas molecules are encapsulated into the cavities to stabilize the overall gas hydrate structure. However, when using refrigerant hydrofluorocarbon-134a (HFC-134a) for guest gas, it resided in resulting brackish water after the desalination process because of its high solubility in water. Jet loop reactors (JLRs) are frequently employed in many commercial applications because of their high mass transfer capabilities. In this study, a semi-batch type JLR was introduced to improve the degassing of HFC-134a from brackish water. The effect of parameters, such as the initial HFC-134a concentration (200–772 mg/L), liquid circulation (40–80 L/min) rate, and air flow rate (10–30 L/min), were studied in this JLR. The removal efficiency and overall volumetric transfer were calculated and it was determined that increasing the air flow rate has a high effect on KLa.

Final report on CCQM-P151: Halocarbons in dry whole air

The growing awareness of climate change/global warming and continuing concerns regarding stratospheric ozone depletion will require future measurements and standards for many compounds, in particular halocarbons that are linked to these issues. In order to track and control the emissions of these species globally in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a pilot study between National Metrology Institutes and atmospheric research laboratories for several of the more important halocarbons at atmospheric concentration levels. The comparison includes the chlorofluorocarbons (CFCs) dichlorodifluoromethane (CFC 12), trichlorofluoromethane (CFC 11), and 1,1,2-trichlorotrifluoroethane (CFC 113); the hydrochlorofluorocarbons (HCFCs) chlorodifluoromethane (HCFC 22) and 1-chloro-1,1-difluoroethane (HCFC 142b); and the hydrofluorocarbon (HFC) 1,1,1,2-tetrafluoroethane (HFC 134a), all in a dried whole air sample. The objective of this key comparison is to compare the measurement capabilities of the participants for these halocarbons at trace atmospheric levels.Main text.To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM.

Final report on international comparison CCQM-K83: Halocarbons in dry whole air

The growing awareness of climate change/global warming and continuing concerns regarding stratospheric ozone depletion will require future measurements and standards for many compounds, in particular halocarbons that are linked to these issues. In order to track and control the emissions of these species globally in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a key comparison for several of the more important halocarbons at atmospheric concentration levels. The comparison includes the chlorofluorocarbons (CFCs) dichlorodifluoromethane (CFC 12), trichlorofluoromethane (CFC 11), and 1,1,2 trichlorotrifluoroethane (CFC 113); the hydrochlorofluorocarbons (HCFCs) chlorodifluoromethane (HCFC 22) and 1-chloro-1,1-difluoroethane (HCFC 142b); and the hydrofluorocarbon (HFC) 1,1,1,2 tetrafluoroethane (HFC 134a), all in a dried whole air sample. The objective of this key comparison is to compare the measurement capabilities of the participants for these halocarbons at trace atmospheric levels.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

승용차 냉방장치로부터의 온실가스 냉매인 HFC-134a 탈루배출모델에 대한 연구

The objective of this research was to develop fugitive emission models of HFC-134a (Hydrofluorocarbon-134a) at the operation and disposal stages of passenger cars. It is essential to estimate the emission of HFC-134a from mobile air conditioner (MAC) due to its high Global Warming Potential (GWP) and extensive use as a refrigerant in MAC. The first-order emission model was introduced and the emission rate constant was assumed to be unvaried with time. A commercial recovery station of refrigerants was used to recover the HFC-134a from the MAC. Average emission rate constant and annual emission rate during the operation period of vehicle are estimated to be <TEX>$0.0538{\pm}0.0092$</TEX> (n=21) <TEX>$yr^{-1}$</TEX> and <TEX>$5.2{\pm}0.6%$</TEX>, respectively within a confidence interval of 95%. According to the model results, about 50% of HFC-134a would be emitted from the MAC during the 10 years operation of passenger cars. On the other hand, average remaining portion of HFC-134a in the MACs of scrap cars is <TEX>$58.2{\pm}4.8%$</TEX> (n=50) within a confidence interval of 95%, suggesting that over 40% of the initially charged amount could be released fugitively after disposal provided that the HFC-134a would not be properly treated or recycled.

Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Advanced Global Atmospheric Gases Experiment (AGAGE) observations at Cape Grim, Tasmania, and Mace Head, Ireland

An update of in situ Advanced Global Atmospheric Gases Experiment (AGAGE) hydrofluorocarbon (HFC)/hydrochlorofluorocarbon (HCFC) measurements made at Mace Head, Ireland, and Cape Grim, Tasmania, from 1998 to 2002 are reported. HCFC‐142b, HCFC‐141b, HCFC‐22 and HFC‐134a show continued rapid growth in the atmosphere at mean rates of 1.1, 1.6, 6.0, and 3.4 ppt/year, respectively. Emissions inferred from measurements are compared to recent estimates from consumption data. Minor updates to the industry estimates of emissions are reported together with a discussion of how to best determine OH concentrations from these trace gas measurements. In addition, AGAGE measurements and derived emissions are compared to those deduced from NOAA‐Climate Monitoring and Diagnostics Laboratory flask measurements (which are mostly made at different locations). European emission estimates obtained from Mace Head pollution events using the Nuclear Accident Model (NAME) dispersion model and the best fit algorithm (known as simulated annealing) are presented as 3‐year rolling average emissions over Europe for the period 1999–2001. Finally, the measurements of HCFC‐141b, HCFC‐142b, and HCFC‐22 discussed in this paper have been combined with the Atmospheric Lifetime Experiment (ALE)/Global Atmospheric Gases Experiment (GAGE)/AGAGE measurements of CFC‐11, CFC‐12, CFC‐113, CCl4, and CH3CCl3 to produce the evolution of tropospheric chlorine loading.

A Life-Cycle Comparison of Several Auxiliary Blowing Agents Used for the Manufacture of Rigid Polyurethane Foam

In a commitment to zero ozone depletion, the United Nations and the U.S. Environmental Protection Agency (EPA) have called for the phase-out of the manufacture and import of hydrochlorofluorocarbons (HCFCs), used as auxiliary blowing agents (ABAs) in the manufacture of polyurethane foams. As a result, more environmentally benign alternative ABAs are being sought by the foam-blowing industry. This study examined the life cycle of HCFC-22, hydrofluorocarbon-134a (HFC-134a), and cyclopentane, which are currently used or considered as potential alternative ABAs in the manufacture of rigid polyurethane foams that serve as insulation in a model North American refrigerator. The raw material extraction/refining, manufacturing, use, and disposal stages of the life cycle of each ABA were considered, and their resulting relative impacts on ozone depletion and global warming were compared. The manufacturing, use, and disposal stages were determined to affect ozone depletion and global warming to the largest extent, emphasizing the need for a greater focus on pollution prevention opportunities in these stages. The HFC-134a life cycle yields no impact on ozone depletion and a significantly decreased global warming impact compared with its predecessor, HCFC-22, and a tradeoff of slightly higher global warming impact and fewer added safety concerns compared with its more flammable counterpart, cyclopentane.

Formation of fluorinated nonionic surfactant microemulsions in hydrofluorocarbon 134a (HFC 134a)

A structurally related series of fluorinated nonionic oxyethylene glycol surfactants of the type C m F 2 m+1 (CH 2) n O[(CH 2CH 2O) p H], denoted C m. n E p (where m=4, 6, or 7, m=1 or 2, and p=4 or 6) were synthesized and their surface behavior in aqueous solution was characterized. The ability of these surfactants to form water-in-hydrofluorocarbon (HFC) propellant 134a microemulsions suitable for use in the aerosolized delivery of water-soluble drugs has been investigated. Phase studies showed that, regardless of the composition used, clear one-phase systems could not be prepared if a fluorinated nonionic surfactant was used alone, or in combination with a short or medium fluorocarbon alcohol cosurfactant. Clear one-phase systems could, however, be prepared if a short-chain hydrocarbon alcohol, such as ethanol, n-propanol, or n-pentanol, was used as cosurfactant, with the extent of the one-phase region increasing with decreased chain length of the alcohol cosurfactant. Light-scattering studies on a number of the hydrocarbon-alcoholcontaining systems in the propellant-rich part of the phase diagram showed that only systems prepared with C 4.2E 6 and propanol contained microemulsion droplets (all other systems investigated were considered to be cosolvent systems).

Fluorinated ionic surfactant microemulsions in hydrofluorocarbon 134a (HFC 134a)

The factors influencing the formation of water-in-134a-propellant microemulsions using the fluorinated ionic surfactants ammonium perfluorooctanoate, ammonium perfluoroheptanoate, and sodium perfluorooctanoate has been determined. None of the fluorinated ionic surfactants could be used to prepare clear, one-phase systems when used as sole surfactant, but they could be when combined with a short-chain fluoro- or hydrocarbon alcohol in surfactant:cosurfactant weight-mixing ratios ( K m) in the range 1:2 to 2:1. When hydrocarbon alcohols were used this clear region extended over a wide range of compositions and was confirmed by means of photon correlation spectroscopy (PCS) to contain microemulsion droplets in the propellant-rich part of the phase diagram. PCS studies performed in the presence of the water-soluble drug terbutaline sulfate showed that it was possible to solubilize the drug within water-in-propellant microemulsion droplets. These studies confirm for the first time that it is possible to prepare water-in-propellant 134a microemulsions using fluorinated ionic surfactants and to solubilize water-soluble drugs within these systems.

Human Safety and Pharmacokinetics of the CFC Alternative Propellants HFC 134a (1,1,1,2-Tetrafluoroethane) and HFC 227 (1,1,1,2,3,3,3-Heptafluoropropane) Following Whole-Body Exposure

HFC 134a (1,1,1,2-tetrafluoroethane) and HFC 227 (1,1,1,2,3,3,3-heptafluoropropane) are used to replace chlorofluorocarbons (CFCs) in refrigerant and aerosol applications, including medical use in metered-dose inhalers. Production and consumption of CFCs are being phased out under the Montreal Protocol on Substances that Deplete the Ozone Layer. The safety and pharmacokinetics of HFC 134a and HFC 227 were assessed in two separate double-blind studies. Each HFC (hydrofluorocarbon) was administered via whole-body exposure as a vapor to eight (four male and four female) healthy volunteers. Volunteers were exposed, once weekly for 1 h, first to air and then to ascending concentrations of HFC (1000, 2000, 4000, and 8000 parts per million (ppm)), interspersed with a second air exposure and two CFC 12 (dichlorodifluoromethane) exposures (1000 and 4000 ppm). Comparison of either HFC 134a or HFC 227 to CFC 12 or air gave no clinically significant results for any of the measured laboratory parameters. There were no notable adverse events, there was no evidence of effects on the central nervous system, and there were no symptoms of upper respiratory tract irritation. HFC 134a, HFC 227, and CFC 12 blood concentrations increased rapidly and in an exposure-concentration-dependent manner, although not strictly proportionally, and approached steady state. Maximum blood concentrations (Cmax) tended to be higher in males than females; in the HFC 227 study, these were statistically significantly (P < 0.05) higher in males for each HFC 227 and CFC 12 exposure level. In the HFC 134a study, the gender difference in Cmax was only statistically significant (P < 0.05) for CFC 12 at 4000 ppm and HFC 134a at 8000 ppm. Following the end of exposure, blood concentrations declined rapidly, predominantly biphasically and independent of exposure concentration. For the HFC 134a study, the t1/2α (α elimination half-life) was short for both CFC 12 and HFC 134a (<11 min). The t1/2β (β elimination half-life) across all exposure concentrations was a mean of 36 and 42 min for CFC 12 and HFC 134a, respectively. Mean residence time (MRT) was an overall mean of 42 and 44 min for CFC 12 and HFC 134a, respectively. In the HFC 227 study, t1/2α for both CFC 12 and HFC 227, at each exposure level, was short (<9 min) and tended to be lower in males than females. For CFC 12 mean t1/2β ranged from 23 to 43 min and for HFC 227 the mean range was 19–92 min. The values tended to be lower for females than males for HFC 227. For both CFC 12 and HFC 227, MRT was statistically significantly lower (P < 0.05) in males than females and independent of exposure concentration. For CFC 12, MRT was a mean of 37 and 45 min for males and females, respectively, and for HFC 227 MRT was a mean of 36 and 42 min, respectively. Exposure of healthy volunteers to exposure levels up to 8000 ppm HFC 134a, 8000 ppm HFC 227, and 4000 ppm CFC 12 did not result in any adverse effects on pulse, blood pressure, electrocardiogram, or lung function.

Condensation of R134a flowing inside helicoidal pipe

Condensing heat transfer and pressure drop characteristics of an ozone-friendly refrigerant HFC-134a (hydrofluorocarbon 134a) flowing inside a 12.7 mm helicoidal tube were investigated experimentally to obtain heat transfer data and correlations. For long helicoidal pipe, heat transfer measurements were performed for the refrigerant flow mass fluxes from 100 to 400 kg/m 2/s, in the cooling water flow Reynolds number range of 1500<Re w <9000 at fixed system temperature (33°C) and cooling tube wall temperature (12°C and 22°C). With the increase of mass flux, the overall condensing heat transfer coefficients of R134a increased, and slowly the pressure drops also increased. However, with the increase of mass flux (or the cooling water flow Reynolds number), the refrigerant side heat transfer coefficients decreased. The effects of cooling wall temperature on heat transfer coefficients and system pressure drops were considered. Predictive correlations valid over the above water flow Reynolds number ranges and refrigerant flow mass flux were proposed. Helicoidal pipe heat transfer characteristics were compared with data for horizontal straight pipe from literature reports.

Mechanism of atmospheric oxidation of 1,1,1,2-tetrafluoroethane (HFC 134a)

The chlorine-initiated photooxidation of hydrofluorocarbon 134a (CF3CH2F) has been studied in the temperature range 235–318 K and at 1 atm total pressure using UV absorption. Trifluoroacetyl fluoride [CF3C(O)F] and formyl fluoride [HC(O)F] were observed as the major products. IR analysis of the reaction mixture also showed carbonyl fluoride [C(O)F2] as a product. By measurement of the yields of [HC(O)F] from the photooxidation as a function of [O2] and temperature, the rate of the unimolecular decomposition of the oxy radical, CF3CHFO, reaction (5), was determined relative to its reaction with O2, reaction (4): CF3CHFO + O2→ CF3C(O)F + HO2(4), CF3CHFO → CF3+ HC(O)F (5) The results were treated using both an arithmetic derivation and numerical integration with a detailed reaction scheme. Inclusion of other recently published kinetic data leads of the following recommended rate expression for reaction (5) at 1 atm k5= 7.4 × 1011 exp[(–4720 ± 220)/T] s–1 The errors are 1σ.The observation of enhanced product yields in the present work is attributed to the reaction of the CF3O radical with HFC 134a leading to further peroxy radical formation. The results have been incorporated into a 2D atmospheric model to assess the environmental implications of HFC 134a release in the troposphere.

Formation of Trifluoroacetic Acid from the Atmospheric Degradation of Hydrofluorocarbon 134a: A Human Health Concern?

Formation of Trifluoroacetic Acid from the Atmospheric Degradation of Hydrofluorocarbon 134a: A Human Health Concern?

Relative rate constants for reactions of HFC 152a, 143, 143a, 134a, and HCFC 124 with F or Cl atoms and for CF2CH3, CF2HCH2, and CF3CFH radicals with F2, Cl2, and O2

AbstractRelative rate experiments using UV photolysis of F2 or Cl2 have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F2 present, dark reactions are, also, observed which are attributed to thermal dissociation of the F2 to form F atoms. At 296 K, the rate of reaction (1a) [CF2HCH3 + F → CF2CH3 + HF] relative to (1b) [CF2HCH3 + F → CF2HCH2 + HF] is k1a/k1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF2HCH2F + F → products] to that of (k1a + k1b) is (k1a + k1b)/k2a = 2.7 (±0.4), and for reaction (2b) [CF3CH3 + F → products] (k1a + k1b)/k2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF3CFH2 + Cl → products] relative to reaction (4) [CF3CFClH + Cl → products] is k3/k4(±10%) = 1.55 exp(−300 K/T). For the alkyl radicals formed from HFC 152a (CF2HCH2 and CF2CH3) and from HFC 134a (CF3CFH), rate constants for the reactions with F2 and Cl2 were measured relative to their reactions with O2. The rate constant of reaction (5cl) [CF2CH3 + Cl2 → CF2ClCH3 + Cl] relative to (5o) [CF2CH3 + O2 → CF2(O2)CH3] is k5cl/k5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF2CH3 + F2 → CF3CH3 + F], k5f/k5o(±35%) = 0.23. The ratio for reaction (6f) [CF2HCH2 + F2 → CF2HCH2F + F] relative to (6o) [CF2HCH2 + O2 → CF2HCH2O2] is k6f/k6o(±40%) = 1.23 exp(−730 K/T). The rate constant ratio for reaction (8cl) [CF3CFH + Cl2 → CF3CFClH + Cl] relative to reaction (8o) [CF3CFH + O2 → CF3CFHO2] is k8cl/k8o(±18%) = 0.16 exp(−940 K/T). For reaction (8f) [CF3CFH + F2 → CF3CF2H + F], k8f/k8o(±35%) = 0.6 exp(−860 K/T). © 1993 John Wiley &amp; Sons, Inc.

Atmospheric chemistry of hydrofluorocarbon 134a. Fate of the alkoxy radical trifluoromethoxy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAtmospheric chemistry of hydrofluorocarbon 134a. Fate of the alkoxy radical trifluoromethoxyJens Sehested and Timothy J. WallingtonCite this: Environ. Sci. Technol. 1993, 27, 1, 146–152Publication Date (Print):January 1, 1993Publication History Published online1 May 2002Published inissue 1 January 1993https://doi.org/10.1021/es00038a016RIGHTS & PERMISSIONSArticle Views149Altmetric-Citations77LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (970 KB) Get e-Alerts Get e-Alerts

Atmospheric chemistry of hydrofluorocarbon 134a: fate of the alkoxy radical 1,2,2,2-tetrafluoroethoxy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAtmospheric chemistry of hydrofluorocarbon 134a: fate of the alkoxy radical 1,2,2,2-tetrafluoroethoxyTimothy J. Wallington, M. D. Hurley, James C. Ball, and Edward W. KaiserCite this: Environ. Sci. Technol. 1992, 26, 7, 1318–1324Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://doi.org/10.1021/es00031a006RIGHTS & PERMISSIONSArticle Views212Altmetric-Citations103LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (961 KB) Get e-Alerts Get e-Alerts