Chlorofluorocarbons Research Articles

Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons

Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measurements of archived air samples and on in situ measurements at stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, we report global abundances, trends, and regional enhancements for HCFC-132b ([Formula: see text]), which is newly discovered in the atmosphere, and updated results for HCFC-133a ([Formula: see text]) and HCFC-31 ([Formula: see text]ClF). No purposeful end-use is known for any of these compounds. We find that HCFC-132b appeared in the atmosphere 20 y ago and that its global emissions increased to 1.1 Gg⋅y-1 by 2019. Regional top-down emission estimates for East Asia, based on high-frequency measurements for 2016-2019, account for ∼95% of the global HCFC-132b emissions and for ∼80% of the global HCFC-133a emissions of 2.3 Gg⋅y-1 during this period. Global emissions of HCFC-31 for the same period are 0.71 Gg⋅y-1 Small European emissions of HCFC-132b and HCFC-133a, found in southeastern France, ceased in early 2017 when a fluorocarbon production facility in that area closed. Although unreported emissive end-uses cannot be ruled out, all three compounds are most likely emitted as intermediate by-products in chemical production pathways. Identification of harmful emissions to the atmosphere at an early stage can guide the effective development of global and regional environmental policy.

Shift of nitrate sources in groundwater due to intensive livestock farming on Jeju Island, South Korea: With emphasis on legacy effects on water management

Time lags between anthropogenic nitrogen inputs and their impacts to nitrate levels cause a misunderstanding for sources and subsequently misguide the groundwater management.We investigated the hydrochemical data of groundwater samples (n = 172 from 49 wells) with chlorofluorocarbons (CFCs)-based groundwater age dating and stable N (δ15N) and O isotopes (δ18O) of nitrate to assess the legacy effect of livestock farming to groundwater in an agricultural area where intensive livestock farming started in the 1970s and illegal dumping of manure wastewater in a lava cave was revealed in 2015. Approximately 90% of the groundwater samples had nitrate concentrations exceeding the natural threshold (5.5 mg/L NO3−) for nitrate contamination and 34% exceeded the World Health Organization's guideline for drinking water quality (44.3 mg/L), indicating severe nitrate contamination. The δ15NNO3 values (5.5 to 24.3‰) in groundwater exceeding the threshold of nitrate showed that livestock manure was a major nitrate source, while ammonium fertilizer also seemed influential given the δ15NNO3 values in the overlapping fields of N sources. Factor analysis of hydrochemical data also supported nitrate contamination by manure as well as by plant farming in the study area. Based on the spatial distribution of nitrate levels and δ15NNO3, livestock farming affected nitrate contamination by illegal manure dumping in the leakage cave. According to a Bayesian mixing model, the contribution of manure wastewater was 33.5 to 81.8% as of 2015–2018, with the rest from fertilizers. Meanwhile, the groundwater ages showed negative correlations with both nitrate levels (r = –0.90) and δ15NNO3 values (r = –0.74) on a log scale, consistent with the increasing N release from livestock farming since the 1960s. In particular, the median value of δ15NNO3 rapidly increased to 9.2‰ in groundwater recharged between the late 1970s and early 1990s when N production exponentially increased, implying a significant effect of livestock farming after the 1980s. Groundwater quality is expected to deteriorate over the next several decades based on the groundwater ages (> 23.5 years), the increased N production from livestock farming, and the legacy effect of N. Long-term groundwater management plans (> 25 years) are required to decrease N loads in the study area, because it takes time for management practices to take effect. The study results are a good reference for groundwater management in regions with a source shift to livestock farming under intensive livestock production systems. Moreover, the chronological study using historical N production, groundwater age data, and dual nitrate isotopes can be applied to other regions with multiple N sources and their shifting for identifying sources and estimating time lags.

Estimate of Hydrochlorofluorocarbons (HCFCs) Emission Variations During 2011-2018 in the Yangtze River Delta, China

Hydrochlorofluorocarbons (HCFCs) with reduced ozone depletion potentials (ODPs) and high global warming potentials (GWPs) are used as temporal substitutes of chlorofluorocarbons, and were regulated by the Montreal Protocol and its adjustment with the 2013 cap and until a complete phase-out by 2030 in Article 5 (developing) countries. Weekly flask measurements for four HCFCs (HCFC-22, HCFC-141b, HCFC-142b, and HCFC-124) were conducted at Lin’an regional background station in the Yangtze River Delta (YRD) over the period of 2011-2018 and the measurements of HCFC-132b and HCFC-133a were started in 2018. The HCFCs emissions in YRD were estimated based on the tracer ratio method using CO and HFC-134a as multi-tracers and the estimated emissions of HCFCs based on CO and HFC-134a agreed well within the uncertainties of each other. The YRD’s HCFC emissions based on CO tracer were 28.8 ± 14.1 kt yr-1 for HCFC-22, 5.8 ± 3.4 kt yr-1 for HCFC-141b, 1.3 ± 0.6 kt yr-1 for HCFC-142b, 0.14 ± 0.11 kt yr-1 for HCFC-124, 0.025 ± 0.022 kt yr-1 for HCFC-132b, and 0.40 ± 0.35 kt yr-1 for HCFC-133a in 2018. HCFC-141b, HCFC-142b, and HCFC-124 emissions have reached peaks during the period of freezing consumption (2013-2014) or the period without emission control (2011-2012) and have all recently undergone substantial declines of 18%, 45%, and 30% in 2018 compared with those for 2011-2012. HCFC-22 emissions showed steadily increased during 2011-2018, but the rate of increase in 2018 was obviously slower than the two previous periods. The YRD’s cumulative emissions, ODP-weighted and CO2-equivalent emissions of the four HCFCs accounted for 20%, 23%, and 18% of the national totals, respectively, for 2011-2017, and the HCFC-133a emissions in the YRD provided 70% to the eastern China emissions and 18% to the global emissions in 2018, thus are important contribution to China’s total emissions and even worldwide.

Numerical Investigations on Supercritical Heat Transfer Characteristics of Environmental Friendly Refrigerants

The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and numerical investigations have been conducted to explore supercritical water, carbon dioxide and R134a as heat transfer working fluids. Hydrofluoroolefin (HFO) and refrigerants blends have been considered the most environment-friendly refrigerants to replace Chlorofluorocarbons (CFCs), Hydrochlorofluoro-carbons (HCFCs) and Hydrofluorocarbons (HFCs). Their main advantage of zero Ozone Depletion Potential (ODP) and comparatively lower Global Warming Potential (GWP) have attracted growing amount of attention to mitigate environmental issues. This work adopts the computational method and takes the environmentally friendly refrigerants to investigate the heat transfer characteristics under widely used shear-stress transport (SST) model. A comprehensive comparison was performed at reduced pressure of 1.10 for supercritical fluids R515A, R1234ze(E) and R134a. The peaks of heat transfer coefficient occurred in the vicinity of pseudo critical temperature for all of these considered fluids; however, R134a resulted in higher heat transfer coefficient, Reynolds number and Prandtl number in comparison with R515A and R1234ze(E). The higher heat transfer coefficient of supercritical fluid R134a is owing to its thermophysical properties and the specific heat plays crucial role in the heat transfer of supercritical fluids. Owing to environmental issues, R515A can be a considerable replacement of R134a. R1234ze(E) is also promising alternative to R134a; however, safety issues should thoroughly concern its mild flammable characteristics.

Groundwater age of spring discharges under changing permafrost conditions: the Khangai Mountains in central Mongolia

Obtaining a better understanding of groundwater dynamics in permafrost zones is a critical issue in permafrost hydrology. This includes assessing the impacts of climate change on permafrost thaw and ground ice-melt. Both permafrost thaw and ground ice-melt can be related to groundwater discharges (i.e. spring discharges), and spring water is an important local water resource; accordingly, changes in these processes can have large impacts on local people and their subsistence activities. To detect permafrost thaw and ground ice-melt in the permafrost zone of Mongolia, groundwater ages of several spring discharges were determined using two transient tracers: tritium (3H) and chlorofluorocarbons (CFCs). Spring water samples were collected seasonally from 2015 to 2019 at seven spring sites around the Khangai Mountains in central Mongolia. The sites included two thermokarst landscapes on the northern and southern sides of the mountains. The 3H and CFC concentrations in the spring water in the thermokarst landscapes were very low, especially on the southern side of the mountains, and the estimated mean groundwater age for these sites was older than that for the other sampled springs. Consequently, the young water ratios of the thermokarst sites were lower than those for the other springs. This ratio, however, showed a gradual increase with time, which indicates that recently recharged rainwater began to contribute to the spring discharge at the thermokarst sites. An atmospheric water budget analysis indicated that net recharge from modern and recent precipitation to shallow groundwater in the summer season was almost zero on the southern side of the mountains. Thus, we inferred that the spring water at the thermokarst sites on the southern side of the mountains contained large amounts of ground ice-melt water.

Novel energy station by natural fluid CO 2

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Design of Environmentally Friendly Air Conditioning System Based on Thermo Electric Peltier Tec1-12706

Environmentally friendly problems have been widely studied in scientific journals, one of which is the use of gases that can damage the environment in a variety of cooling devices such as refrigerators and air conditioners (AC). In the past two decades, most of the refrigeration engines were still using Chloro Fluoro Carbons (CFC) gas, which had been researched in fact could damage the ozone layer. One alternative is to use freon gas to replace CFC gas as a component of air conditioning. Until now, CFC gas has been completely replaced by freon gas in the use of household appliances. But the use of this gas still has a bad side, especially for humans, when it inhaled in a certain amount can cause death. Therefore, in this study an air conditioning device with a main component was designed using thermoelectric TEC1-12706 which utilizes the Peltier effect in producing cold temperatures. This device is able to cooling a room with dimension 12 m2 in the interval of time 120 minutes to a temperature of 28.1 °C.

Effects of vehicular emissions on the urban environment- a state of the art

A jerky aspect of the pollutants from the road transportation sector is widening swiftly. The utilization of motor vehicles has been expanding day by day due to the intensive raise of the population. Many studies have illustrated that the peak levels of vehicular pollutants contribute to air pollution. On-road motor vehicles such as cars, bikes and trucks are the major source of emissions. The emissions such as chlorofluoro carbons which are introduced into the atmosphere due to different human activities leads to depletion of ozone layer which directly or indirectly effects the climate. Due to these increased emissions the global environment is facing immeasurable changes which can impact the climate as well as the human health. Air quality is one of the leading troubles in our society and there are numerous factors that effect the quality of air and one of them is Vehicular emission. This paper mainly focuses on how vehicular emissions contribute to climate change from a study made through different literature papers. The parameters and the methodologies that influence the environmental change as well as the human health were extracted from the literature survey and are discussed in this paper. The connection between the air quality and the climate change is also mentioned, since the greenhouse gases influences the quality of air and leads to the ozone depletion. Through this study, one can identify the causes of vehicular emissions towards climate change and there by effecting the human health. The main motive of this research is to present a structured analysis of various causes as well as impacts of vehicular pollution on the environment and climate with the help of the available literature. The study concludes that, the reduction of vehicular pollution is not only favourable for cities but also important for improving the global climate change.

Thermal conductivity prediction of Trans-1-Chloro-3,3,3-Trifluoropropene (R1233zd (E))

R1233zd(E), trans-1-chloro-3,3,3,-trifluoropropene, is a fluorinated propene isomer which may be considered as an alternative working fluids in the field of heat pump and organic Rankine cycle. R1233zd(E) has a much lower GWP than hydrochlorofluorocarbons (HCFC) and their mixtures. In this paper an extension of a previously developed predictive methods for thermal conductivity to a new family of organic compounds, namely R1233zd(E) is considered. A study of the correlation of thermal conductivities of polyatomic gases in the limit of zero density of R1233zd(E) is presented. A theorically correlation scheme based on the formalism Mason-Monchik-Parker theory has been examined and found to be useful for prediction of thermal conductivity data of dilute gas. An attempt is made in this work on the theoretical approach by Predvoditelev, Vargaftik and Filippov proposed for prediction of thermal conductivity for liquid state. The scheme has been tested against the limited amount of experimental data available and shown to be capable of reproducing the thermal conductivities to within few percent. This predicting approach appears promising as an assist in the judgments in the area of this new generation of working fluids data studies.

Monitoring Chlorofluorocarbons in Potential Source Regions in Eastern China

Recent studies have indicated that Eastern China might be a potential source region of increased atmospheric chlorofluorocarbons (CFCs). To investigate this possibility, a field measurement was carried out from October to December 2017 for identifying the ambient concentration levels of representative trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trifluorotrichloroethane (CFC-113), and tetrafluorodichloroethane (CFC-114) at the residential and municipal solid waste (MSW) landfills and industrial sites in Eastern China. The ambient mixing ratios of CFCs at residential sites were almost within 20% enhancements of the global background sites. The highest levels of CFCs were observed at the MSW landfill sites. Moreover, CFC-11 and CFC-113 concentrations at MSW landfill, which was in service, were two times higher than that at completed MSW landfill. Mean concentrations of 322 pptv for CFC-11, 791 pptv for CFC-12, 91 pptv for CFC-113, and 16 pptv for CFC-114 at various industrial sites were higher than those at residential sites, but they were obviously lower than that at MSW landfill in use. A poor intercorrelation between the CFCs indicated that they did not come from the same source. Higher concentrations measured in this study compared with background sites indicates that MSW landfills could be an unintentional emission source and there are still substantial amounts of CFCs being stored in banks that may discharge CFCs into the atmosphere in Eastern China.

Environmental tracers to evaluate groundwater residence times and water quality risk in shallow unconfined aquifers in sub Saharan Africa

In sub-Saharan Africa, shallow aquifer systems are relied on as the main safe and secure water resource available to rural communities. Information on the sustainability and vulnerability of groundwater abstraction is becoming increasingly important as groundwater development increases. As part of the UpGro Consortium Project- Hidden Crisis, 150 hand pumped boreholes (HPBs), ranging between 15 and 101 m depth were investigated to examine the resilience of aquifer systems in the Ethiopian Highlands, and the crystalline basement rocks of Uganda and Malawi. Environmental tracers (chlorofluorocarbons (CFCs), SF6, chloride and the stable isotopes of water), water quality indicators (nitrate and E. coli), and groundwater-level time series data were used to estimate groundwater residence time and recharge at a regional scale (100–10,000 km2) and investigate the risks to water quality and water supply over different timeframes, and geological and climatic environments. Average estimated recharge rates using three different techniques (CFCs, chloride mass balance, water table fluctuation method) were between 30 and 330, 27–110 and 30–170 mm y−1, for sites in Ethiopia, Uganda and Malawi, respectively. These estimates of recharge suggests abstraction from dispersed low-yielding HPBs is sustainable. Comparison of stable isotopes in rainfall and groundwater indicates that there is little evaporation prior to recharge, and recharge events are biased to months with greater rainfall and more intense rainfall events There was a weak correlation between nitrate and CFCs within all three countries, and no correlation between E. coli and CFCs within Ethiopia or Malawi. The presence of E. coli at a large proportion of the sites (Ethiopia = 38%, Uganda = 65% and Malawi = 47%) suggests rapid transit of contaminated surface water into the borehole and its presence in groundwater that has CFC-12 concentrations less than 75 pg kg−1 indicates mixing of very young water with water >40 years old. The rapid transit pathways are most likely associated with damaged HPB headworks and poor construction. In several monitored HPBs, daily drawdown due to pumping, drew the groundwater levels close to the base of the HPB, indicating that these HPBs were located in parts of the aquifer with low permeability, or were poorly designed, offering limited capacity for increased demand. Improved HPB siting and construction, coupled with groundwater level monitoring are required to capitalise on the more resilient groundwater within the shallow aquifers and safeguard adequate and good quality water supply for rural communities.

Interpreting Groundwater Chemistry and Estimating Residence Time of Groundwater in the Mt. Fuji Area Based on a Dissolution Kinetics-Fluid Flow Model and Chlorofluorocarbons (CFCs) Concentration

Relationships of concentrations of elements (Ca, Mg, Si) in groundwater from the Mt. Fuji area are obtained using analytical data on groundwater. Relationships of Ca, Mg, and H4SiO4 concentrations can be explained in terms of the dissolution of basaltic glass and precipitations of secondary minerals (halloysite, allophane, montmorillonite, and α-cristobalite). The relationship between residence time and H4SiO4 concentration of groundwater is obtained based on dissolution kinetics-piston fluid flow and a perfectly mixing fluid flow model. Using this relationship, the dissolution rate constant experimentally determined in an open system (not in a closed system) (k = 10−10.7 molSi/m2 s) and analytical data on H4SiO4 in groundwater, the residence time of groundwater (Kakitagawa site, southeastern foot and Fuji Yoshida site, northern foot) is estimated to be ca. 20 years for A/M (A: surface area of rock (m2), M: mass of water (kg)) = 20 based on a dissolution kinetics-fluid flow model. This estimated residence time is roughly consistent with other methods (He isotope tritium, chlorofluorocarbons (CFCs) ages (10-40 years), indicating that the dissolution kinetics-fluid flow model using dissolved silica concentration is a potentially useful method for estimating the residence time of groundwater in a young volcanic region. It is also reported that CFCs ages are ca. 30-40 years, which are the first data obtained for the Mt. Fuji area. This suggests that CFCs data are very useful for providing the residence time of groundwater in an area at a high elevation.

Chemistry Nobelist Mario Molina dies

Mario Molina, who shared the 1995 Nobel Prize in Chemistry for work on understanding the formation and decomposition of ozone in the stratosphere, died Oct. 7 at his home in Mexico City. He was 77. “Arguably, I think his work saved humans,” says Renyi Zhang, an atmospheric sciences professor at Texas A&M University. Zhang was Molina’s first doctoral student when the Nobel laureate was a professor at the Massachusetts Institute of Technology. In 1974, Molina was a postdoc under F. Sherwood Rowland at the University of California, Irvine, when the two published a ground-breaking paper in Nature (DOI: 10.1038/249810a0 ). They hypothesized that chlorofluorocarbons (CFCs), synthetic gases then widely used as refrigerants and aerosol propellants, could deplete stratospheric ozone, which absorbs most of the sun’s ultraviolet light and makes life on Earth possible. Chemical manufacturers and aerosol producers scoffed at the idea. But other scientists confirmed and built on Molina

Ozone Depletion and Global Environment

This paper is focused on the relationship between ozone depletion and environmental climate change. Ozone (O3) depletion and global warming are not directly related to each other but have a common reason as pollutants released into the atmosphere by human activities which alter both phenomenal change. Global warming is incident of accumulation of higher level of carbon dioxide into the atmosphere when hydrocarbons are used to generate electricity to run vehicles. Carbon dioxide spreads around the earth like a cover which is mainly responsible for the absorption of infrared radiation as a heat. Ozone depletion occurs when chlorofluorocarbons (CFCs) and halon (halogen) gases are observed in aerosol. Practically, spray cans and refrigerants are the sources of CFCs. Ozone is available in the stratosphere and absorbs ultraviolet radiaton, which is very harmful to humans, animals and plants. By photochemical reaction ozone molecules are broken down by CFCs and halons, which are the primary substances in the chemical reactions, reducing ozone’s ultraviolet radiation-absorbing capacity.

Senators strike deal for US phasedown of HFCs

Breaking a legislative deadlock that has extended through most of this year, key senators announced a deal for the US to phase down hydrofluorocarbon (HFC) production over the next 25 years. HFCs are refrigerants used in air conditioners and commercial freezers, among other applications. Chemical makers introduced them as replacements for stratospheric ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) . HFCs are potent greenhouse gases, and emissions of these chemicals are increasing worldwide. Sens. Tom Carper (D-DE) and John Kennedy (R-LA) an HFC phasedown. They ran into opposition from Sen. John Barrasso (R-WY), chairman of the Senate Environment and Public Works Committee, and other Republicans who raised concerns about possible adverse impacts on consumers and small businesses. In , Barrasso, Carper, and Kennedy agreed to HFC language that will be tacked onto that could progress in Congress in coming weeks. As Carper and Kennedy sought, the deal would require the US

Experimental measurement and modelling of vapor-liquid equilibrium for 3,3,3- Trifluoropropene (R1243zf) and trans-1,3,3,3-Tetrafluoropropene (R1234ze(E)) binary system

• Experimental measurement of VLE data for R1243zf + R1234ze(E) by a static analytical method. • The R1243zf + R1234ze(E) system is a zeotropic system within 283.15 to 323.14 K. • Experimental data show good agreement with the predicted results of PR-MC-vdW and PR-MC-MHV2 models. The environmental performance becomes the critical factor of the selection of refrigerant. 3,3,3-trifluoropropene (R1243zf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) are environmental friendly candidates to replace R134a. Whereas, in the consideration of environmental factor, safety, and energetic efficiency at the same time, none of the pure refrigerants has been proved to be a suitable solution. Mixed refrigerants provide an approach to this problem because the characteristics of refrigerant blends can be optimized for particular applications in the way pure component refrigerant alone cannot be. The purpose of this work is to explore an R1243zf/R1234ze(E) blend which can be possibly used as a long-term alternative to replace hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). We report the measurements of saturated vapor pressures of R1234ze(E) and R1243zf ranging from 273.17 to 353.13 K, and isothermal vapor-liquid equilibrium of R1243zf + R1234ze(E) systems from 283.15 to 323.14 K. The measurements are performed by static-analytic type apparatus coupled with two electromagnetic capillary samplers (ROLSI®, patent of Armines). The experimental data are correlated by the Peng-Robinson (PR) equation of state (EoS) associated with Mathias-Copeman (MC) alpha function and classical mixing rules. For the comparison of conventional mixing rules and excess free energy ( G E ) mixing rules models, classic van der Waals one fluid mixing rules and modified Huron-Vidal second-order (MHV2) mixing rules are employed respectively to the correlation of experimental VLE data. The modeling results are in good agreement with the measured data, while the PRMC-MHV2 model exhibits better performance in VLE prediction.

Lag Time as an Indicator of the Link between Agricultural Pressure and Drinking Water Quality State

Diffuse nitrogen (N) pollution from agriculture in groundwater and surface water is a major challenge in terms of meeting drinking water targets in many parts of Europe. A bottom-up approach involving local stakeholders may be more effective than national- or European-level approaches for addressing local drinking water issues. Common understanding of the causal relationship between agricultural pressure and water quality state, e.g., nitrate pollution among the stakeholders, is necessary to define realistic goals of drinking water protection plans and to motivate the stakeholders; however, it is often challenging to obtain. Therefore, to link agricultural pressure and water quality state, we analyzed lag times between soil surface N surplus and groundwater chemistry using a cross correlation analysis method of three case study sites with groundwater-based drinking water abstraction: Tunø and Aalborg-Drastrup in Denmark and La Voulzie in France. At these sites, various mitigation measures have been implemented since the 1980s at local to national scales, resulting in a decrease of soil surface N surplus, with long-term monitoring data also being available to reveal the water quality responses. The lag times continuously increased with an increasing distance from the N source in Tunø (from 0 to 20 years between 1.2 and 24 m below the land surface; mbls) and La Voulzie (from 8 to 24 years along downstream), while in Aalborg-Drastrup, the lag times showed a greater variability with depth—for instance, 23-year lag time at 9–17 mbls and 4-year lag time at 21–23 mbls. These spatial patterns were interpreted, finding that in Tunø and La Voulzie, matrix flow is the dominant pathway of nitrate, whereas in Aalborg-Drastrup, both matrix and fracture flows are important pathways. The lag times estimated in this study were comparable to groundwater ages measured by chlorofluorocarbons (CFCs); however, they may provide different information to the stakeholders. The lag time may indicate a wait time for detecting the effects of an implemented protection plan while groundwater age, which is the mean residence time of a water body that is a mixture of significantly different ages, may be useful for planning the time scale of water protection programs. We conclude that the lag time may be a useful indicator to reveal the hydrogeological links between the agricultural pressure and water quality state, which is fundamental for a successful implementation of drinking water protection plans.

Performance analysis of bismuth-antimony-telluride-selenium alloy-based trapezoidal-shaped thermoelectric pallet for a cooling application

The zero emission and chlorofluorocarbons (CFC) free thermoelectric cooling systems have the potential to limit the adverse effect on our climate due to the greenhouse gas emission from traditional cooling technologies. In this paper, a new configuration of thermoelectric cooling system is proposed, which includes trapezoidal-shaped solid-state thermoelectric legs, bismuth-antimony-telluride-selenium alloy, and it is manufactured using environmentally friendly handheld dispenser fabrication method. The synthesized thermoelectric materials are characterized using x-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscope (SEM) technologies in order to study the morphology of the materials. Both theoretical and experimental studies are performed on trapezoidal and rectangular prototypes. It is identified that the trapezoidal-shaped leg requires less material (nearly 25% less) and exhibits lower thermal conductance (around 27% less) in comparison with the rectangular-shaped TE leg. Experimental results further show that a maximum temperature difference of 79.4 °C can be achieved from the trapezoidal-shaped prototype at 5A input current which is 10% higher than the rectangular prototype. Besides, an experimentally validated analytical model is used to investigate further the cooling capability, temperature difference, and coefficient of performance of both trapezoidal and rectangular-shaped TEC. A range of area ratio of the hot surface to the cold surface of the TE leg varying from 0.33 to 3 has been studied. In addition, the maximum COP of the trapezoidal-shaped prototype is approximately 32.5% higher than the rectangular prototype. The maximum obtainable cooling rate and temperature difference are almost the same but require nearly 50% less input current to achieve this maximum output with a hot to cold surface area ratio of 0.33.

Theoretical investigation of electron impact on formyl fluoride (HFCO)

In this paper, a descriptive and detailed theoretical analysis is carried out on electron scattering of formyl fluoride (HFCO) covering a wide impact energy range of 0.1 eV–5000 eV. Due to such a wide impact energy range, we were able to calculate the variety of interaction processes such as eigen phase study to infer about the resonances, vertical electron excitations, differential cross-sections, momentum transfer cross-sections, ionization cross-sections and total scattering cross-sections for electron impact on formyl fluoride. To compute these cross-sections for this energy range, we have used an amalgamation of two theoretical methodologies namely R-matrix via. Quantemol-N, valid for the low energy calculations from 0.1 eV to 20 eV and the Spherical Complex Optical Potential (SCOP) applicable from ionization threshold of the target to 5000 eV. There is a smooth cross over of total cross-sections observed between these two methods at the incident energy just below 20 eV. The present study becomes more important as it presents the electron impact cross-sections on HFCO for the first time and thus provides a reference data set for HFCO over an extensive impact energy range. The data set is important as Hydrofluorocarbons (HFCs) are one class of potential chlorofluorocarbons (CFC) substituents which mainly reacts with the OH radical in the atmosphere leading to the formation of the dominant intermediate product HFCO.

Subsurface hydrological processes and groundwater residence time in a coastal alluvium aquifer: Evidence from environmental tracers (δ18O, δ2H, CFCs, 3H) combined with hydrochemistry

As an important part of the water cycle, the hydrologic process and chemical compositions of groundwater have changed significantly due to the joint influence of climate change and human activities. Groundwater salinization becomes a serious threat to water security in coastal areas. In order to assess the relationships between surface water, groundwater and seawater in the coastal plain, we performed a synthesis study based on hydrochemical-isotopic data, hydro-dynamical records and environmental tracers. Deuterium and oxygen isotopes and water chemical indicators were used to identify pollution status, salt sources and migration processes. Radioactive isotopes and gaseous tracers were used to obtain reasonable groundwater age. With the help of multi-tracer approach, the surface-groundwater interaction, salinization of groundwater and nitrate pollution were identified in the Yang-Dai River plain, northern China. The estimated groundwater ages determined from chlorofluorocarbons (CFCs) and tritium (3H) ranges from 18 to 41 years in this area, suggesting a modern groundwater circulation. The spatial distribution of the groundwater age varies significantly due to horizontal hydrogeological heterogeneity. The total dissolved solids (TDS) content of the groundwater near the Well Field (average: 970 mg/L) was higher than the TDS values in samples derived from places located at an equivalent distance to the coastal line (average is 708 mg/L), which resulted from the vertical seawater intrusion through river channels and pollutant inputs from agriculture activities. The nitrate concentrations in groundwater were elevated up to 271 mg/L and increased with increasing groundwater age, which was another water environment problem that should be solved urgently but lacks sufficient attention for years. This study provides a conceptual model with a number of comparable hydrochemical information, which is significant for regional pollution control and water resources management.