Kigali Amendment Research Articles

Natural refrigerant matching optimization and characteristic analysis of two-stage Rankine cycle for LNG cold power generation process

Unlike most waste heat recovery, LNG is a multi-component mixture, low temperature and wide boiling range make it difficult to achieve efficient recovery of cold energy with a conventional single-stage Rankine cycle. On the other hand, with the stricter restrictions on hydrofluorocarbons under the Kigali Amendment, more environmentally friendly natural refrigerants deserve more attention as alternatives. Therefore, to improve the recovery efficiency of cold energy, this paper studied the optimal natural refrigerant combination of two-stage Rankine cycle LNG cold energy power generation system, and analyzed the performance characteristics and influencing factors of the system. In addition, in order to verify the application potential of the system, the levelized cost of electricity and payback period of the system for different refrigerant combinations were also analyzed. The results show that at a delivery pressure of 0.6 MPa, the refrigerant combination of ‘ethylene + propane’ has the best power generation performance, with a net generation and exergy efficiency of 9020.8 kW and 35.54 %, respectively. The refrigerant combination of ‘ethylene + propylene’ has the best economic performance, with a levelized power cost and payback period of 0.0355 USD/kWh and 2.76 years, respectively. In the case of high delivery pressure requirements, ‘ethane + propane’ becomes the optimal refrigerant combination, which can simultaneously achieve optimal power generation performance and economic performance. In addition, as the delivery pressure decreases, the power generation and economic performance of the system will improve. It is also found that among all refrigerants, ethane and ethylene have the highest evaporation pressure, which is conducive to obtaining a greater effective enthalpy drop, but the required superheat is also larger, which reduces the heat transfer efficiency of the evaporator to a certain extent.

Exploring Synergistic GHG Emissions Mitigation Potential and Costs of Room Air Conditioners.

This study explores the potential of synergistically reducing direct (refrigerant) and indirect (electricity) greenhouse gas (GHG) emissions in the global room air conditioning (RAC) sector, based on 80% of global RAC manufactured in China. Three scenarios are evaluated: Business-as-usual (BAU) based on maintaining refrigerant and energy efficiency levels from 2021 China RAC sales shares, Kigali Amendment compliant with 10% energy efficiency improvement by 2025 (KAE), and accelerated refrigerant transition and energy efficiency improvement (ATE). Each scenario considers the costs of refrigerant and efficiency measures for export market groups based on Kigali Amendment classifications. BAU predicts around 1 Gt CO2-eq average annual global RAC emissions (2022-2060). Cumulative emission reductions in China's RAC manufacturing under KAE and ATE are 12.2 and 17.2 Gt CO2-eq A5II and A5I (except China), presenting cost-effective abatement measures, with average costs of -$51.4 and -$68.8/t CO2-eq in KAE and ATE. Cumulative average abatement costs are around $18 and $4/t CO2-eq globally. KAE and ATE scenarios would avoid surface temperature rises of 0.023 (±0.002) °C and 0.027 (±0.003) °C, respectively, versus BAU. Collaboration between China and importing countries is urged to enhance energy efficiency in RACs traded, ensuring sustainable mitigation aligned with the Kigali Amendment.

Environmental Policies and Countermeasures for the Phase-Out of Ozone-Depleting Substances (ODSs) over the Last 30 Years: A Case Study in Taiwan

It is well established that the reaction cycles involving some halogenated alkanes (so-called ozone-depleting substances—ODSs) contribute to the depletion of ozone in the stratosphere, prompting the Montreal Protocol (initially signed in 1987), and later amendments. The Protocol called for the scheduled phase-out of ODSs, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CCl4), halon, methyl chloroform (CH3CCl3), methyl chloride (CH3Cl), and even hydrofluorocarbons (HFCs). In view of the urgent importance of ozone layer protection to the global ecological environment, the Taiwanese government has taken regulatory actions to reduce ODS consumption since 1993, through the joint venture of the central competent authorities. Under the government’s regulatory requirements, and the industry’s efforts to adopt both alternatives to ODSs and abatement technologies, the phase-out of some ODSs (i.e., CFCs, CCl4, halon, and CH3CCl3) was achieved prior to 2010. The consumption of HCFCs and methyl chloride has significantly declined over the past three decades (1993–2022). However, HFC emissions indicated a V-type variation during this period. Due to local production and extensive use of HFCs in Taiwan, the country’s emissions increased from 663 kilotons of carbon dioxide equivalents (CO2eq) in 1993 to 2330 kilotons of CO2eq in 2001, and then decreased to 373 kilotons of CO2eq in 2011. Since then, the emissions of HFCs largely used as the alternatives to ODSs showed an upward trend, increasing to 1555 kilotons of CO2eq in 2022. To be in compliance with the Kigali Amendment (KA-2015) to the Montreal Protocol for mitigating global warming, the Taiwanese government has taken regulatory actions to reduce the consumption of some HFC substances with high global warming potential (GWP) under the authorization of the Climate Change Response Act in 2023, aiming at an 80% reduction by 2045 of the baseline consumption in 2024.

Climate change, energy transition, and the Global South: learnings from the international framework on the ozone layer

The pursuit of climate action to meet net-zero targets has triggered the call for a global energy transition from fossil fuels to clean energy sources. However, this global energy transition does not entirely recognise all countries’ social, economic and technological capacities as well as emission contributions as envisaged under the Common but Differentiated Responsibilities (CBDR) principle, which underlies international climate policy. It is concerned more with the outcome of transitioning to clean energy than with justice in the transition process. Recognition justice, an element of energy justice, enables us to identify the inequalities that global energy paradigms (such as the energy transition) can create and how a justice framework can help us understand the implications of energy injustice and address the inequities across energy systems. Recognition justice acknowledges the divergent perspectives rooted in social, economic and racial differences and the varied strengths of developed and developing countries. The energy transition process ought to recognise these differences so that they are reasonably expected to benefit everyone. Implementing the energy transition in the Global South (GS) in the same way as it is being advanced in the Global North will have security, justice, economic, resource-stranding, and sustainable development implications. This issue (of injustice in the energy transition) is aggravated by two dichotomous realities: many countries in the South will be most impacted by climatic changes, yet there remains political and social opposition to climate action through the energy transition. As a solution, this paper relies on the notion of recognition justice with support from the Rawlsian justice concept to argue that a delayed transition represents justice and recognises the peculiar nature and different circumstances of the GS. It identifies that learnings from the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer and the notion of CBDR under international climate treaties can be mainstreamed into energy transition research and policies to achieve justice for countries of the GS. The paper further finds that a delayed transition for the GS will (i) enable the region to address sustainability-related issues of hunger and multidimensional poverty, essential to realising other Sustainable Development Goals, whilst gradually implementing energy transition policies; (ii) present an attractive case against political and social opposition to energy transition in the GS; (iii) advance the goal of CBDR already recognised under international climate treaties and the bifurcated approaches established in such treaties; and, finally, (iv) ensure that developed countries contributing the most to greenhouse gas emissions take the lead now and act while the GS effectuates national contributions sustainably.

Analysis of refrigerants used in supermarket commercial equipment and the potential for increasing energy efficiency and reducing environmental impact

Refrigerants used in the commercial equipment of supermarkets are the object of the research. The Montreal Protocol calls for a complete phase-out of hydrochlorofluorocarbons (HCFCs) by 2030, and the Kigali Amendment regulates the use of hydrofluorocarbons (HFCs) from 2019. Developed countries began phasing out HFC use in 2019, while developing countries plan to freeze HFC consumption from 2024. These global efforts are aimed at reducing the depletion of the ozone layer and combating climate change. The number of supermarkets in the world varies greatly: in Europe they number from 110 thousand to 115 thousand, and in China – from 65 thousand to 70 thousand, which reflects various needs in refrigeration equipment. Stringent environmental regulations are forcing the commercial refrigeration sector to remain globally competitive. Modernization of supermarkets using natural refrigerants is important for solving emerging challenges. The results of the study show significant improvements in energy efficiency ratio (EER) and coefficient of performance (COP) when using a mixture of hydrocarbons (R290: 85 %, R600a: 15 %) compared to traditional refrigerants R404a, R449a and R502. Specifically, at the evaporation temperature of Tevap=–10 °C, EER increased by 38–44 % and COP by 26–31 % compared to R404a and R449a, respectively. At Tevap=–25 °C, EER increased by 17–34 % and COP by 2–22 % compared to R404a and R449a. Additionally, compared to R502, the hydrocarbon blend showed a 38–44 % increase in EER and 28–31 % COP at Tevap=–10 °C, and a 17–34 % increase in EER and 5–22 % COP at Tevap=–25 °C. These results highlight the advantages of the hydrocarbon mixture at different evaporation temperatures, indicating its potential to improve energy efficiency in refrigeration applications. The obtained data suggest the possibility of a wider application of the mixture of hydrocarbons in commercial refrigeration plants, offering both improved performance and compliance with safety regulations.

Revealing the significant acceleration of hydrofluorocarbon (HFC) emissions in eastern Asia through long-term atmospheric observations

Abstract. Hydrofluorocarbons (HFCs) are powerful anthropogenic greenhouse gases (GHGs) with high global-warming potentials (GWPs). They have been widely used as refrigerants, insulation foam-blowing agents, aerosol propellants, and fire suppression agents. Since the mid-1990s, emissions of HFCs have been increasing rapidly as they are used in many applications to replace ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) whose consumption and production have been phased out under the Montreal Protocol (MP). Due to the high GWP of HFCs, the Kigali Amendment to the MP requires the phasedown of production and consumption of HFCs to gradually achieve an 80 %–85 % reduction by 2047, starting in 2019 for non-Article 5 (developed) countries with a 10 % reduction against each defined baseline and later schedules for Article 5 (developing) countries. In this study, we have examined long-term high-precision measurements of atmospheric abundances of five major HFCs (HFC-134a, HFC-143a, HFC-32, HFC-125, and HFC-152a) at Gosan station, Jeju Island, South Korea, from 2008 to 2020. Background abundances of HFCs gradually increased, and the inflow of polluted air masses with elevated abundances from surrounding source regions were detected over the entire period. From these pollution events, we inferred regional and country-specific HFC emission estimates using two independent Lagrangian particle dispersion models and Bayesian inversion frameworks (FLEXPART-FLEXINVERT+ and NAME-InTEM). The spatial distribution of the derived “top-down” (measurement based) emissions for all HFCs shows large fluxes from megacities and industrial areas in the region. Our most important finding is that HFC emissions in eastern China and Japan have sharply increased from 2016 to 2018. The contribution of East Asian HFC emissions to the global total increased from 9 % (2008–2014) to 13 % (2016–2020). In particular, HFC emissions in Japan (Annex I country) rose rapidly from 2016 onward, with accumulated total inferred HFC emissions being ∼ 114 Gg yr−1, which is ∼ 76 Gg yr−1 higher for 2016–2020 than the “bottom-up” (i.e., based on activity data and emission factors) emissions of ∼ 38 Gg yr−1 reported to the United Nations Framework Convention on Climate Change (UNFCCC). This is likely related to the increase in domestic demand in Japan for refrigerants and air-conditioning-system-related products and incomplete accounting. A downward trend of HFC emissions that started in 2019 reflects the effectiveness of the F-gas policy in Japan. Eastern China and South Korea, though not obligated to report to the UNFCCC, voluntarily reported emissions, which also show differences between top-down and bottom-up emission estimates, demonstrating the need for atmospheric measurements, comprehensive data analysis, and accurate reporting for precise emission management. Further, the proportional contribution of each country's CO2-equivalent HFC emissions has changed over time, with HFC-134a decreasing and HFC-125 increasing. This demonstrates the transition in the predominant HFC substances contributing to global warming in each country.

Fluorinated ZIF-71 with adjusted pore size to enhance separation performance of mixed matrix membrane for recovering R32 from R410A

Due to the high Global Warming Potential (GWP) of hydrofluorocarbons (HFCs), the Kigali Amendment to the Montreal Protocol explicitly calls for the phase-out or limited use of HFCs, and the replacement of HFCs by hydrofluoroolefins (HFOs) is imminent. Therefore, it is particularly significant to develop new technology to separate valuable difluoromethane (R32, GWP = 675) from the near-azeotropic refrigerant blend R410A (GWP = 2088), because the traditional distillation is not applicable. In this work, aiming to enhance the separation performance of mixed matrix membrane (MMMs) for R410A, 5-fluorobenzimidazole was introduced into ZIF-71 by the solvent assisted linker exchange (SALE) method for the first time to reduce the pore size of fluorinated ZIF-71 by benzene rings and form hydrogen bonds between R32 with ZIF-71. A novel series of MMMs consisting of fluorinated ZIF-71 and Poly(ether-block-amide) ®1657 (Pebax®1657) polymer were prepared to separate the components of the R410A. The separation performance of the MMMs was investigated at different feed pressures and filler loading. The results showed that the introduction of 5-fluorobenzimidazole contributed to a significant increase in R32 permeability and R32/R125 selectivity of the MMMs compared to pure Pebax membrane. The 15 wt% ZIF-71-F/Pebax MMM showed the best separation performance with R32/R125 selectivity up to 26.6, four times that of pure Pebax membrane and twice that of ZIF-71/Pebax MMM. The ZIF-71-F/Pebax MMM have outstanding data on R32/R125 selectivity and no significant disadvantage in permeability, far exceeding the reported separation performance of membranes for R410A. This confirms that the application of fluorinated metal organic frameworks (MOFs) to the separation of refrigerant blends is a promising strategy.

More to offer from the Montreal protocol: how the ozone treaty can secure further significant greenhouse gas emission reductions in the future

ABSTRACT Action under the Montreal Protocol has contributed to climate change mitigation for almost 35 years. The phase-out of ozone-depleting substances (ODS) has set the ozone layer on a path to recovery, protecting the world’s biosphere from harmful ultraviolet radiation. The 2016 Kigali Amendment to the Montreal Protocol is expected to avoid 5.6–8.7 gigatonnes of carbon-dioxide equivalent (GtCO2e) emissions of hydrofluorocarbons (HFC) per year by 2100, reducing the impact of HFCs on global average warming by up to 0.4°C. Despite its successes, unexpected emissions of phased out ODS – notably the chlorofluorocarbon, CFC-11 - have brought attention to shortcomings in the Protocol’s monitoring, reporting, verification and enforcement (MRV+E) which must be addressed to guarantee its controls are sustained. Meanwhile, additional significant mitigation could be achieved by accelerating the phase-down of HFCs under the Kigali Amendment, by tackling ODS and HFC emissions from leaking banks of equipment and products and by controlling feedstocks, which are not subject to Montreal Protocol phase-out controls. Recent scientific papers have linked almost 870 million tCO2 per year of greenhouse gases (GHG) and ODS to fluorochemical industrial processes and illegal fluorochemical production. Expanding the scope of the Montreal Protocol to address nitrous oxide (N2O), itself an ODS and GHG, would also contribute substantial ozone and climate benefits. This perspective essay discusses new and strengthened policy measures that governments can consider under the Montreal Protocol in order to maximize early, cost-effective reductions in emissions of non-CO2 greenhouse gases and ensure future implementation.

Estimate Gaps of Montreal Protocol-Regulated Potent Greenhouse Gas HFC-152a Emissions in China Have Been Explained.

1,1-Difluoroethane (HFC-152a) is a hydrofluorocarbon regulated by the Montreal Protocol, and its emissions in China are of concern as China will regulate HFC-152a in 2024. However, no observation-inferred top-down estimates were undertaken after 2017, and substantial gaps existed among previous estimates of China's HFC-152a emissions. Using the atmospheric observations and inverse modeling, this study reveals China's HFC-152a emissions of 9.4 ± 1.7 Gg/yr (gigagrams per year), 10.6 ± 1.8 Gg/yr, and 9.7 ± 1.5 Gg/yr in 2018, 2019, and 2020, respectively. In addition, we display an overall increasing trend during 2011-2020, which is in contrast to the decreasing and steady trend reported by the Emission Database for Global Atmospheric Research (EDGAR) and the Chinese government, respectively. Subsequently, we establish a comprehensive bottom-up emission inventory matching with top-down estimates and thus succeed in explaining the gaps among previous estimates. Furthermore, the contribution of China's emissions to global HFC-152a emission growth increased from 15% during 2001-2010 to >100% during 2011-2020. An emission projection based on our improved inventory shows that the Kigali Amendment (KA) would assist in avoiding 1535.6-4710.6 Gg (251.8-772.5 Tg CO2-eq) HFC-152a emissions during 2024-2100. Our findings indicate relatively accurate China's HFC-152a emissions and provide scientific support for addressing climate change and implementing the KA.

Isothermal (vapor ＋ liquid) equilibrium measurements and correlation of the binary mixture 3,3,3-trifluoropropene (R1243zf) ＋ isobutane (R600a) at temperatures from [formula omitted] to [formula omitted] K

The restrictions set by the F-gas Regulation and the Kigali Amendment to the Montreal Protocol have pushed an extensive research into alternatives for fluorinated greenhouse gases in air conditioning and refrigeration. Hydrofluoroolefins (HFOs) are emerging as promising substitutes for hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) in HVAC and refrigeration. Amongst these, R1243zf raised interests as low-GWP substitutes for R134a. The pursuit of low GWP refrigerants has also led to the examination of hydrocarbons (HCs), like propane (R290) and isobutane (R600a), due to their efficiency, low charge, and affordability, despite their flammability. The mixtures of R1243zf and isobutane could be of interest for medium temperature heat pump applications. Moreover, blending HFOs with HCs usually leads to azeotropic mixtures. While HCs benefit of a wide range of data and reliable Equations of State (EoS), HFOs, and in particular their mixtures, lack comprehensive information. This study reports vapor–liquid equilibrium (VLE) measurements for the 3,3,3-trifluoropropene (R1243zf) + isobutane (R600a) binary system in the temperature range between 283.15 K and 323.15 K. The measurements have been carried out by means of a vapor-recirculation apparatus combined with gas-chromatographic analysis. This work reports 53 experimental data with an expanded uncertainty (k=2) of 0.003 mol mol−1. The reported data, along with the data available in the literature, have been used to developed two new mixture models based on the Helmholtz free energy EoS, both leading to a significant improvement in the VLE prediction, with RMSE values lower than 0.005 mol mol−1 for both the liquid and the vapor phase composition.

О возможности взрыва при применении экологически безопасных хладагентов в холодильном оборудовании

Today, the most common domestic electric equipment is a household refrigerator. The use of flammable substances as refrigerants for refrigerators can lead to severe consequences. As the production of hydrofluorocarbon class refrigerants for refrigeration equipment was restricted by the Kigali amendment to the Montreal Protocol, refrigeration technologies have been transferred from using hydrofluorocarbon class refrigerants to natural refrigerants (propane, butane, isobutane). The replacement of hydrofluorocarbon class refrigerants with natural refrigerants is already noticeable since in many cases isobutane (R-600a) is used as a refrigerant for refrigeration equipment. Isobutane is a combustible substance with a wide explosion limit (1.8–9.5 % vol.); hence, it is classified as an A2 refrigerant class of hazard (combustible substances). As R-600a is classified as an A2 class of fire hazard, its use in refrigeration technologies is limited with the refrigerant mass; therefore, the use of R-600a for refrigeration equipment is considered safe. According to international and Russian data, however, some accidents involving the use of flammable refrigerants in refrigeration equipment were registered. In the US, two explosions of serviceable household refrigerators were registered; in the Russian Federation, one explosion of refrigeration equipment during repair jobs was registered. According to the parameters of refrigeration equipment explosion, R-600а was used as a refrigerant. This study provides a calculation of excess pressure of explosion in case of leakage of R-600a from a refrigerator in the volume of a living accommodation (kitchen) in order to estimate the fire safety of combustible refrigerants. Based on the results of calculations, it has been concluded that the existing norms of the use of combustible refrigerants are insufficient and cannot ensure fire-explosion and fire safety for a person and refrigeration equipment.

Usage of R513A as an alternative to R134a in a refrigeration system: An experimental investigation based on the Kigali amendment

In this study, the use of the alternative refrigerant R513A instead of R134a in a mechanical vapor compression refrigeration system was experimentally investigated in terms of the first and second laws of thermodynamics on the basis of the Kigali Amendment. The investigations were carried out approximately at a cooling medium temperature (TL) of 0, 4, and 8 °C and a heating medium temperature (TH) of 30, 35, and 40 °C without any modifications to the system. The energetic and exergetic performance parameters obtained in this study were related to the amount of refrigerant in accordance with the criteria restricting the use of fluorinated greenhouse gases after the Kigali Amendment. Accordingly, the required refrigerant mass flow rate per unit energetic (power input, cooling capacity, COP value) and exergetic (total exergy destruction rate and exergy efficiency) performance parameters were determined. As a result, the system was found to operate safely when R513A was used instead of R134a without any modification. In addition, the refrigerant mass flow rate per unit power input was almost the same for both refrigerants. However, R513A was found to have approximately 15 % more refrigerant mass flow per unit cooling capacity than R134a. This resulted in the refrigerant mass flow rate per unit COP being approximately 20 % higher for R513A. On the other hand, the refrigerant mass flow rate per unit exergy efficiency calculated for R513A was found to be about 15 % higher than R134a.

The Social Costs of Hydrofluorocarbons and the Large Climate Benefits from their Expedited Phasedown.

Hydrofluorocarbons are a potent greenhouse gas, yet there remains a lack of quantitative estimates of their social cost. The present study addresses this gap by directly calculating the social cost of hydrofluorocarbons (SC-HFCs) using perturbations of exogenous inputs to integrated assessment models. We first develop a set of direct estimates of the SC-HFCs using methods currently adopted by the United States Government, and then derive updated estimates that incorporate recent advances in climate science and economics. We compare our estimates with commonly used social cost approximations based on global warming potentials to show that the latter is a poor proxy for direct calculation of hydrofluorocarbon emissions impacts using IAMs. Applying our SC-HFCs to the Kigali Amendment, a global agreement to phase down HFCs, we estimate that it provides $37 trillion (2020USD) in climate benefits over its lifetime. Expediting the phasedown could increase the estimated climate benefits to $41 trillion (2020USD).

Rwanda Towards the Implementation of Montreal Protocol on Substances that Deplete the Ozone Layer. the Current Status of ODS, Ods Alternatives, and HFCS Alternatives.

In August 2003, Rwanda ratified both the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol on Substances that Deplete the Ozone Layer, along with all the subsequent amendments, including the Kigali Amendment, which was most recently ratified in May 2017. Within this context, by the Law n°63/2013 of 27/08/2013, Rwanda Environment Management Authority (REMA) was created with the legal mandate for national environmental protection, conservation, promotion and overall management, including advisory to the government on all matters pertinent to the environment and climate change. According to Decision XIX/6 of the 19th Meeting of the Parties to the Montreal Protocol on accelerated phase-out of HCFCs, Rwanda is committed to phase-out use of HCFCs by 2030 except for 2.5% for servicing essential use appliances up to 2040. The Hydro chloro fluorocarbons Phase-out Management Plan (HPMP) Stage-I for Rwanda was approved at the 64th Meeting of the Executive Committee for the period 2011 to 2020 to meet a 35% reduction of HCFC by 2020. The HPMP Stage-II has been approved by the 86th meeting of the Executive Committee of the Multilateral Fund Secretariat, to be implemented by UNEP, UNIDO and REMA to enable Rwanda achieve phase-out targets on consumption of Annex C Group 1 Substances of the Montreal Protocol by 2030. The HPMP Stage-II has prioritized key activities to be implemented which include: establishment and implementation of a robust certification scheme for refrigeration technicians, development and implementation of national technical standards in the Refrigeration and Air-Conditioning (RAC) sector that will promote safe use of natural refrigerants and further promote use of highly energy efficiency technologies, capacity building of refrigeration technicians on handling natural refrigerants, training of customs and other enforcement officers on controlling and monitoring HCFC trade and strengthening the Refrigeration Association of Rwanda, technical training institutes and the consumers.The implementation of HPMP Stage-II activities will enable RWANDA reduce consumption of HCFC-22 from the baseline of 4.1 ODP tonnes to 80 percent by 2025 and 100 percent by 2030.This paper represents the results of the national survey conducted to inform the preparation of the project proposal for Kigali HFC Implamentation plan as well as the strategic KIP/HFC phase-down plan.

Experimental investigation on boiling heat transfer characteristics of R1234yf/R1336mzz(Z) in horizontal flow

Due to the inclusion of 18 HFCs, including R134a and R245fa, in the Kigali Amendment as controlled working fluids, the search for excellent alternatives to R134a and R245fa is urgent. R1234yf and R1336mzz(Z) are potential alternative working fluids to R134a and R245fa, but most studies have focused on the comparison of thermodynamic performance and boiling heat transfer capability of these pure working fluids. There is limited research on the boiling heat transfer performance of their mixed working fluids. Therefore, this study focuses on the flow boiling heat transfer characteristics of the mixed working fluid R134a/R245fa under non-azeotropic conditions. Experimental methods were employed to investigate the boiling heat transfer performance of the alternative working fluids R1234yf/R1336mzz(Z) (including R245fa/R1234yf and R1234yf/R1336mzz(Z) mixed working fluids) and evaluate the feasibility of R1234yf and R1336mzz(Z) as substitutes for R134a and R245fa. The results indicate that among the three mixed refrigerants, R134a/R245fa exhibits the highest heat transfer coefficient, while R1234yf/R1336mzz(Z) shows the lowest heat transfer coefficient. However, the differences in heat transfer coefficients among these three are relatively small, and their overall trends under different operating conditions are similar. It is evident that R134a/R245fa, with its good thermodynamic performance and stability, still holds potential as a transitional working fluid. R1234yf/R1336mzz(Z), with similar physical and thermodynamic properties, is an excellent alternative to R134a/R245fa.

Experimental and Numerical Studies on an Automobile Air Conditioning System With the Refrigerants R134a, R1234yf, and R1234ze(E)

Abstract The Montreal Protocol of 1987 has put the chlorofluorocarbons (CFCs) into the category of ozone-depleting substances. The hydrofluorocarbons (HFCs), synthesized as alternatives to CFCs, though possess zero ozone-depleting potential, have high global warming potential (GWP). Despite this, numerous applications currently employ HFCs for refrigeration and air conditioning. The 2016 Kigali amendment to the Montreal Protocol suggested a phase out of the HFCs, and this process will go on until 2036 in developed nations and until 2047 in developing nations to accomplish a condition of 85% decrease in the use of HFCs. The refrigerant R134a used in mobile air conditioning has a global warming potential (GWP100) of 1300, which prompted researchers to look for new low GWP refrigerants. Recent research has revealed that the HydroFluoroOlefin (HFO) refrigerants R1234yf and R1234ze(E) with a GWP100 of 4 or less show promise for application in the automobile air conditioning (AAC) field. The AAC requires special attention due to frequent leakages of HFC caused by vibration-induced pipe failures. In this research, the low GWP refrigerants R1234yf and R1234ze(E) are considered to explore the AAC system performance, and comparisons are made with the currently used refrigerant R134a. The numerical simulations are performed by including and excluding liquid-to-suction heat exchanger/internal heat exchanger (IHX). The results show that the use of IHX is advantageous for both R1234yf and R1234ze(E). Even though R134a performed better, R1234yf with IHX is a better low GWP alternative in the current AAC system working with R134a without IHX, with only a slight compromise in the system performance and the performance of R1234yf is better than R1234ze(E). Finally, the numerical simulation results are validated against the experimental results for R134a and R1234yf and found that most of the results agree within 10% deviation for system without IHX and within 15% deviation for system with IHX. Thus, if the AAC systems change to R1234yf with an IHX, the directives set out in the Kigali amendment of 2016 to Montreal Protocol (namely the discontinuation of HFCs for refrigeration) will be satisfied without any significant loss in the performance.

Solubility of difluoromethane (R-32) and pentafluoroethane (R-125) in 1-alkyl-3-methylimidazolium tricyanomethanide ionic liquids

The recovery of refrigerant blends and the subsequent separation of value-added hydrofluorocarbons (HFCs) for reuse would help to meet the phase-down in the production of virgin HFCs established by the Kigali Amendment to the Montreal Protocol. The use of ionic liquids (ILs) in extractive distillation processes has become particularly relevant. In this process, the selection of the IL is the core element for a technically and economically feasible design. For this purpose, the absorption of the HFCs difluoromethane (R-32) and pentafluoroethane (R-125), components of the equimassic mixture R-410A, in 1-alkyl-3-methylimidazolium tricyanomethanide ILs was studied. The isochoric saturation method was applied to report vapor-liquid equilibrium data over a temperature range of 283.15–323.15 K and up to 0.9 MPa. These data were fitted accurately to the NRTL activity coefficient model and the Henry's law constants, the activity coefficients at infinite dilution, the enthalpies and entropies of solvation and the thermodynamic mixing properties were calculated. Finally, [C2C1im][tcm] ranked as one of the most selective ILs to date, exhibiting a good R-32 absorption capacity that could make it a valuable solvent for the separation of R-410A by extractive distillation.

Mitigation potential of banned hydrofluorocarbons (HFCs) towards global warming – An assessment of Kigali Amendment in the Indian scenario

In order to combat the climate change resulting from climate forcing agents such as hydrofluorocarbons (HFCs), Kigali Amendment to Montreal Protocol was proposed in 2016. India gave its nod to Kigali Amendment, where the phase down of HFCs will take place in four steps from 2032 to 2047. In the present study, the emission scenarios for five majorly used HFCs in India, HFC-125, HFC-134a, HFC-143a, HFC-152a and HFC-227ea, with and without Kigali Amendment are developed. In the absence of Kigali Amendment, the GWP weighted emissions of these HFCs are estimated to increase to 0.16 GtCO2 eq. in 2050 from 0.09 GtCO2 eq in 2020. The Kigali Amendment reduction target for these emissions is estimated to be ∼0.03 GtCO2 eq. in 2050. Except for HFC-134a, the other HFCs have almost zero RF by 2050 in the presence of Kigali Amendment. The atmospheric oxidation potential of HFCs calculated through their reaction with atmospheric OH/Cl radicals reveal that HFC-134a is degraded rapidly in the atmosphere, whereas the oxidation potential of HFC-143a is very low. This leads to a longer lifetime of HFC-143a in the atmosphere. Thus, GWP alone is not a metric in determining the climate forcing properties of HFCs. In addition, the atmospheric oxidation potential, product toxicity and chemical stability should also be included as policy-relevant metrics and the Kigali Amendment should be revisited in including the compounds based on these metrics.

Regarding the Montreal Protocol communication after the Kigali Amendment

Abstract The Kigali Amendment introduced a new family of chemical compounds, which do not contribute to stratospheric ozone depletion but present a high global warming potential, under the watch of the Montreal Protocol in 2016. Earlier this year, a press note from the World Meteorological Organization entitled “Ozone layer recovery is on track, helping avoid global warming by 0.5°C” caught our attention because of the wrong conclusions that can be potentially drawn by laypersons due to an apparent linkage of ozone depletion and global warming problems. Public communication of the Montreal Protocol since the Kigali Amendment should be more careful than ever to avoid lessening the social perception of the threat of climate change, particularly considering that society already has a distorted representation of these problems, assuming causal relations between ozone depletion and climate change, that could lead to unfounded optimism towards the climate crisis.

Trifluoroiodomethane as a Precursor to High Global Warming Potential Climate Pollutants: Could the Transformation of Climatically Benign CF3I into Potent Greenhouse Gases Significantly Increase Refrigerant-Related Greenhouse Gas Emissions?

The transition away from the production and consumption of high global warming potential (GWP) hydrofluorocarbons (HFCs) under the 2016 Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) has prompted air conditioning, refrigeration, and heat pump equipment manufacturers to seek alternative refrigerants with lower direct climate impacts. Additional factors affecting alternative refrigerant choice include safety (i.e., flammability and toxicity), environmental, and thermodynamic constraints. At the same time, manufacturers are incentivized to seek refrigerants with higher energy efficiency, which saves on electricity costs and reduces indirect greenhouse gas emissions from electricity generation. The life cycle climate performance (LCCP) metric is commonly used to assess the combined direct and indirect climate impacts of refrigerant-use equipment. Here, we consider an additional impact on climate performance: the degradation of refrigerant in equipment, i.e., the direct climate impacts of high-GWP byproducts that can form as the result of adding trifluoroiodomethane (CF3I) to refrigerant blends to reduce flammability. Such a production of high-GWP gases could change the acceptability of CF3I-containing refrigerants. Further, it highlights the need to understand refrigerant degradation within equipment in calculations of the environmental acceptability of new cooling technology.