Hydrofluoroolefins Research Articles

An innovative ocean thermal energy conversion system with zeotropic Rankine cycle and direct contact membrane distillation for enhanced efficiency and sustainability

This research introduces an integrated ocean thermal energy conversion water and power cogeneration system (OTEC-WPCS), combining a Zeotropic Rankine Cycle (ZRC) with Direct Contact Membrane Distillation (DCMD) for efficient power and water production. The hydrofluoroolefins (HFOs), chosen for their zero ozone depletion potential (ODP) and extremely low global warming potential (GWP), are used as working fluid components in the ZRC. Additionally, DCMD is implemented for freshwater generation. A mathematical model is established, incorporating both thermodynamic and CFD simulations. The goal is to identify optimal operating conditions that maximize the output of the system. By coupling DCMD and ZRC in series, the system's efficiency reaches 8.92 %, an improvement of 5.71 % compared to a standalone ZRC system. This configuration allows for more efficient use of surface seawater heat compared to an ammonia-based Organic Rankine Cycle (ORC)-DCMD system. The enhancements include an increase in power and water production per unit mass flow of surface seawater by 0.55 kW/(kg·s) and 30 %, respectively. Over 60 % of the system's exergy destruction occurs in the DCMD modules and evaporator, while nearly 80 % of the capital cost is associated with the evaporator, condenser, and DCMD heat exchanger. Enhancing the DCMD module structure and heat exchanger can improve both energy and exergy efficiency, and economic feasibility.

Environment-Friendly Refrigerants for Sustainable Refrigeration and Air Conditioning: A Review

Refrigeration and air conditioning systems play a vital role in our modern society, and refrigerants are integral components of these systems. Traditional refrigerants like chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) have caused significant environmental concerns because of their role in ozone depletion and global warming. Consequently, interest has increased in developing and implementing environmentally benign refrigerants possessing minimal global warming potential (GWP) and no ozone depletion potential (ODP). This review explores the emerging field of environment-friendly refrigerants such as natural refrigerants (NH3, CO2, hydrocarbons), hydrofluoroolefins (HFOs), hydrofluorocarbons (HFCs) with ultra-low GWP, hydrofluoroethers (HFEs) and mixtures or blends of these refrigerants. The article also compares their thermophysical, thermodynamic, environmental and safety properties, and their suitability for different applications. The key recommendations encompass the promotion of natural refrigerants, including NH3, CO2, and hydrocarbons, exhibit minimal environmental effects. Additionally, the exploration of HFOs and HFCs with ultra-low GWP and their mixtures as potential substitutes is advised. Transitioning to environment-friendly refrigerants is essential for achieving sustainable refrigeration and air conditioning systems, mitigating climate change, and ensuring the long-term viability of cooling technologies while preserving the environment.

Molecular Simulation Studies on the Vapor-Liquid Equilibrium of CO2 + 3,3,3-Trifluoropropene (R1243zf) Binary Mixtures.

As fourth-generation refrigerants with great development prospects, hydrofluoroolefins (HFOs) can be mixed with other refrigerants, such as carbon dioxide (CO2), to form refrigerant mixtures with low global warming potential (GWP) and zero ozone depleting potential (ODP) while retaining the advantages of each component. Refrigerants can work together to achieve complementary benefits. Combinations of CO2 and HFOs can strengthen the thermodynamic properties of CO2 while inhibiting the flammability of HFOs. At present, relatively few studies have been conducted on the CO2 + 3,3,3-trifluoropropene (R1243zf) mixture. Besides experimental approaches, molecular simulation has grown in importance as a way to determine thermodynamic and transport properties in recent years. In this study, the Gibbs Ensemble Monte Carlo (GEMC) method was used to simulate the vapor-liquid equilibrium (VLE) properties of the CO2 + R1243zf binary mixture in the temperature range of 273.15 to 313.15 K, in which the three-site rigid TraPPE force field and a fully flexible transferable all-atom force field were selected to describe CO2 and R1243zf, respectively. By comparing the GEMC simulation results with the experimental data, it was found that the average deviation of pressure is 2.33%, the average deviation of liquid phase molar fraction Δx is 0.0099, and the mean deviation of gaseous phase molar fraction Δy is 0.0204. The simulation results accord well with the experimental data and the fitting data of the correlation model in the literature, indicating that the molecular models used for CO2 and R1243zf can reliably predict the VLE properties. Finally, the critical parameters of the mixture at a temperature of 313.15 K were predicted, and the radial distribution functions (RDFs) of pure R1243zf and the mixture at 273.15 K and 3.5 MPa were calculated and analyzed by molecular dynamics (MD) simulation.

Finding non-fluorinated alternatives to fluorinated gases used as refrigerants.

Hydrofluorocarbons (HFCs) and so-called hydrofluoroolefins (HFOs) are used as refrigerants in air conditioning, refrigeration, chillers, heat pumps and devices for dehumidification and drying. However, many HFCs, including R-134a and R-125, have a high global warming potential and some of the HFCs and HFOs degrade atmospherically and form trifluoroacetic acid (TFA) as a persistent degradation product. Rising levels of TFA around the globe reveal an urgent need to replace fluorinated refrigerants with non-fluorinated working fluids to avoid direct emissions due to leakage, incorrect loading or removal. It is important, however, also to select refrigerants with high efficiencies to avoid increasing indirect CO2 emissions due to higher energy consumption during the use phase. The present study investigates the available non-fluorinated alternatives to fluorinated refrigerants and shows that a transition to non-fluorinated refrigerants, in general, is possible and has happened in many sectors already. Technically, there are only slight barriers to overcome in order to replace fluorinated refrigerants in almost all newly developed systems conforming to existing standards. Additionally, we show that alternatives are available even for some use cases for which derogations have been proposed in the EU PFAS restriction proposal and suggest making these derogations more specific to support a speedy transition to non-fluorinated refrigerants in all sectors.

Iodonium based regioselective double nucleophilic alkene functionalization of a hydrofluoroolefin scaffold.

Herein, we report a modular regioselective alkene difunctionalization strategy based on the use of hydrofluoroolefin (HFO) gas as fluorous feedstock material. The transformation of the HFO gas to iodonium salt creates vicinal electrophilic sites readily available for a broad range of nucleophiles.

The Analysis of Next-Generation Refrigerants in Terms of Energy, Exergy, and LCCP Perspective

In this study, commonly used hydrofluorocarbon (HFC)-based refrigerants R404A and R410A, as well as hydrofluoroolefin (HFO)-based environmentally friendly next-generation refrigerant R1234yf with a low global warming potential (GWP), were analyzed in terms of energy, exergy, and life cycle climate performance (LCCP) in refrigeration and air conditioning systems. All three refrigerants were examined at four different evaporation temperatures (-30°C, -15°C, -5°C, 0°C) with a constant condenser temperature of 50°C using a simulation program. For different evaporation temperatures, the performance of the refrigerants was evaluated using the first and second laws of thermodynamics, and performance coefficients, exergy efficiency, and exergy destruction were calculated. Additionally, the amount of kgCO₂e equivalent was calculated using the LCCP method. In the study, it was found that the compressor energy consumption of R410A and R1234yf refrigerants was similar and approximately 7% lower than that of the R404A refrigerant. The highest coefficient of performance (COP) value was determined for R1234yf. It was observed that R1234yf refrigerant had the highest exergy efficiency starting from -15°C. The kgCO₂e equivalent emission values calculated using the LCCP method revealed that R404A had the highest CO₂ emissions, while R1234yf had the lowest. Furthermore, based on the simulation study and theoretical calculations, it was determined that R410A and R1234yf refrigerants could be considered as alternative choices to R404A refrigerants in systems where two refrigerants are used.

Study of vapor compression refrigeration system with suspended nanoparticles in the low GWP refrigerant.

The rising global temperatures, attributed to the high global warming potential (GWP) of conventional refrigerants, necessitate the adoption of low-GWP alternatives in HVAC systems. However, these low-GWP refrigerants often exhibit high toxicity and flammability, limiting their usage. To address these challenges, compact heat exchangers incorporating blended refrigerants have been introduced to enhance HVAC system performance. Researchers have also made significant strides in improving HVAC system efficiency by introducing the concept of suspending nanolubricants and nanorefrigerants within the system. This review paper seeks to comprehensively assess the potential of alternative refrigerants containing suspended nanoparticles, commonly referred to as nanorefrigerants. The paper reviews various mechanisms and potential combinations of different nanorefrigerants employed to enhance refrigeration system effectiveness and efficiency. A detailed examination of key heat transfer parameters and the performance predictions of low-GWP refrigerants, including those from the hydrofluoroolefin (HFO) and hydrocarbon (HC) classes, is conducted through energy and exergy analyses. Commercial refrigerants like R-134a, R-290, R-600, R-600a, R-123, R-125, R-22, R-141b, R-152, R-11, R-113, R-404a, R-407c, R-502, R-600a, R-507a, R-1234yf, R-1234ze, 1336mzz(Z), and R-410a are evaluated in conjunction with suspended nanoparticles, considering their specific properties. The findings indicate that the utilization of nanorefrigerants leads to notable improvements in overall system performance, characterized by reduced compressor workloads and increased heat transfer rates. Consequently, the integration of blended nanoparticles into refrigerants holds significant promise for advancing the HVAC field.

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.

Influence of Long-Term Storage and UV Light Exposure on Characteristics of Polyurethane Foams for Cryogenic Insulation.

Rigid polyurethane (PUR) foams have been the most effective insulation material used in space launchers since the beginning of cryogenic fuel use, due to their outstanding thermal and mechanical properties. In this study, spray-applied PUR foams using different ratios of amine-based catalysts were produced. Due to climate change, several restrictions have been made regarding the usage of blowing agents used for PUR foam production. Lately, hydrofluoroolefins (HFOs) have been suggested as an alternative for PUR foam production due to their low global warming potential (GWP) and ozone depletion potential (ODP), replacing the hydrofluorocarbons (HFCs) so far used. This change in blowing agents naturally altered the usage of catalysts. Reactive amine-based catalysts are less hazardous because of their low volatility and ability to react successfully with isocyanate or polyols. Spray-applied PUR foams with a potential application for cryogenic insulation were produced and tested for long-term storage, analyzing parameters such as the pH value of polyol composition, foaming kinetics (trise, tcream), etc. Athermal analysis (TG, DSC) was also applied to developed materials, as well as artificial ageing by exposing samples to UV light. It was discovered that PUR foams obtained using reactive amine-based catalysts, such as Polycat 203 and 218, have a higher integral heat capacity, but polyol mixtures containing these catalysts cannot exceed a storage time of more than 4 months. It was also observed from artificial ageing tests of PUR cryogenic insulation by exposure to UV light that the thickness of the degraded layer reached 0.8 mm (after 1000 h), but no significant destruction of cellular structure deeper in the material was observed.

Thermodynamic and economic performance evaluations of double-stage organic flash cycle using hydrofluoroolefins (HFOs)

Organic flash cycle is an important way to achieve geothermal power generation. Double-stage organic flash cycle (DOFC) has two flash processes, remarkably enhancing the heat matching effect of heat absorption process compared to single-stage type. Working fluid is an important factor influencing the performance superiority of DOFC. However, traditional organic fluids are being phased out due to environmental requirements, the new-type hydrofluoroolefins are emerging with good environmental performance. For new-type hydrofluoroolefins, the characteristics of DOFC are unclear and its advantages over single-stage type need to be quantified. This work evaluates the thermodynamic, exergy and economic performance of DOFC using ten eco-friendly hydrofluoroolefins. Influences of key parameters on thermodynamic and economic performance are analyzed. For hydrofluoroolefins, the superiorities of DOFC over single-stage type were quantitatively evaluated. Results show that the advantages of DOFC will become greater at the lower heat source temperature and the lower critical temperature of hydrofluoroolefins. R513A shows the greatest advantages of DOFC over single-stage type, and the maximum relative increment in the net power is 111.2 % and the maximum relative decrement in specific investment cost is 49.5 %. The optimum hydrofluoroolefin is R1366mzz(Z) with a net power of 348.29 kW and a specific investment cost of 7.88 k$·kW−1.

Nickel‐Catalyzed Selective C(sp2)−F Bond Alkylation of Industrially Relevant Hydrofluoroolefin HFO‐1234yf

AbstractThe selective transition‐metal catalyzed C−F bond functionalization of inexpensive industrial fluorochemicals represents one of the most attractive approaches to valuable fluorinated compounds. However, the selective C(sp2)−F bond carbofunctionalization of refrigerant hydrofluoroolefins (HFOs) remains challenging. Here, we report a nickel‐catalyzed selective C(sp2)−F bond alkylation of HFO‐1234yf with alkylzinc reagents. The resulting 2‐trifluoromethylalkenes can serve as a versatile synthon for diversified transformations, including the anti‐Markovnikov type hydroalkylation and the synthesis of bioactive molecule analogues. Mechanistic studies reveal that lithium salt is essential to promote the oxidative addition of Ni0(Ln) to the C−F bond; the less electron‐rich N‐based ligands, such as bipyridine and pyridine‐oxazoline, feature comparable or even higher oxidative addition rates than the electron‐rich phosphine ligands; the strong σ‐donating phosphine ligands, such as PMe3, are detrimental to transmetallation, but the less electron‐rich and bulky N‐based ligands, such as pyridine‐oxazoline, facilitate transmetallation and reductive elimination to form the final product.

Nickel-Catalyzed Selective C(sp2 )-F Bond Alkylation of Industrially Relevant Hydrofluoroolefin HFO-1234yf.

The selective transition-metal catalyzed C-F bond functionalization of inexpensive industrial fluorochemicals represents one of the most attractive approaches to valuable fluorinated compounds. However, the selective C(sp2 )-F bond carbofunctionalization of refrigerant hydrofluoroolefins (HFOs) remains challenging. Here, we report a nickel-catalyzed selective C(sp2 )-F bond alkylation of HFO-1234yf with alkylzinc reagents. The resulting 2-trifluoromethylalkenes can serve as a versatile synthon for diversified transformations, including the anti-Markovnikov type hydroalkylation and the synthesis of bioactive molecule analogues. Mechanistic studies reveal that lithium salt is essential to promote the oxidative addition of Ni0 (Ln ) to the C-F bond; the less electron-rich N-based ligands, such as bipyridine and pyridine-oxazoline, feature comparable or even higher oxidative addition rates than the electron-rich phosphine ligands; the strong σ-donating phosphine ligands, such as PMe3 , are detrimental to transmetallation, but the less electron-rich and bulky N-based ligands, such as pyridine-oxazoline, facilitate transmetallation and reductive elimination to form the final product.

Modeling the Ground- and Excited-State Unimolecular Decay of the Simplest Fluorinated Criegee Intermediate, HFCOO, Formed from the Ozonolysis of Hydrofluoroolefin Refrigerants.

Hydrofluoroolefins (HFO) are fourth-generation refrigerants designed to function as efficient refrigerants with no ozone depletion potential and zero global warming potential. Despite extensive studies on their chemical and physical properties, the ground- and excited-state chemistry of their atmospheric oxidation products is less well understood. This study focuses on the ground- and excited-state chemistry of the simplest fluorinated Criegee intermediate (CI), fluoroformaldehyde oxide (HFCOO), which is the simplest fluorinated CI formed from the ozonolysis of HFOs. HFCOO contains syn- and anti-conformers, which have Boltzmann populations of, respectively, 87 and 13% at 298 K. For both conformers, the calculated ground-state reaction energy profiles associated with cyclization to form fluorodioxirane is lower than the equivalent unimolecular decay path in the simplest CI, H2COO, with anti-HFCOO returning a barrier height more than half of that of H2COO. The excited-state dynamics reveal that photoexcitation to the bright S2 state of syn-HFCOO and anti-HFCOO is expected to undergo a prompt O-O fission─with the former conformer expected to dissociate with an almost unity quantum yield and to form both O (1D) + HFCO (S0) and O (3P) + HFCO (T1) products. In contrast, photoexcitation of anti-HFCOO is expected to undergo an O-O bond fission with a non-unity quantum yield. The fraction of photoexcited anti-HFCOO that dissociates is predicted to exclusively form O (1D) + HFCO (S0) products, which is in sharp contrast to H2COO. The wider implications of our results are discussed from both physical and atmospheric chemistry perspectives.

Scaling theories for predicting the viscosity of binary and ternary refrigerant mixtures

Modeling the viscosity of potential replacements for refrigerants like hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) is important because this information can be used to determine which refrigerants are suitable for use in different refrigeration systems and to guide decisions about system design, operation, and maintenance. In this work, the viscosities of four selected refrigerants, two HFCs and two HFOs, and their mixtures were calculated using two similar approaches, namely entropy scaling and Helmholtz scaling. In both cases, the polar perturbed-chain statistical associating fluid theory (PPC-SAFT) EoS provides the molecular parameters and the entropy or Helmholtz energy dependency required. Results indicate good predictive capabilities for both models, with comparable error to the available experimental data. Even so, the Helmholtz scaling exhibits superior overall robustness, given its extra adjustable parameter. However, predictive results tend to be the same or less quality than those given by the entropy scaling approach.

First Atmospheric Measurements and Emission Estimates of HFO-1336mzz(Z).

For the past few years, short-lived unsaturated halocarbons have been marketed as environmentally friendly replacements for long-lived halogenated greenhouse gases and ozone-depleting substances. The phase-in of unsaturated halocarbons for various applications, such as refrigeration and foam blowing, can be tracked by their emergence and increase in the atmosphere. We present the first atmospheric measurements of the hydrofluoroolefin (HFO) HFO-1336mzz(Z) ((Z)-1,1,1,4,4,4-hexafluoro-2-butene, cis-CF3CH═CHCF3), a newly used unsaturated hydrofluorocarbon. HFO-1336mzz(Z) has been detected in >90% of all measurements since 2018 during multi-month campaigns at three Swiss and one Dutch location. Since 2019, it is found in ∼30% of all measurements that run continuously at the Swiss high-altitude Jungfraujoch station. During pollution events, mole fractions of up to ∼10 ppt were observed. Based on our measurements, Swiss and Dutch emissions were estimated at 2-7 Mg yr-1 (2019-2021) and 30 Mg yr-1 (2022), respectively. Modeled spatial emission distributions only partly conform to population density in both countries. Monitoring the presence of new unsaturated halocarbons in the atmosphere is crucial since long-term effects of their degradation products are still debated. Furthermore, the production of HFOs involves climate-active substances, which may leak to the atmosphere─in the case of HFO-1336mzz(Z), for example, the ozone-depleting CFC-113a (CF3CCl3).

Modeling the Unimolecular Decay Dynamics of the Fluorinated Criegee Intermediate, CF3CHOO

When volatile alkenes are emitted into the atmosphere, they are rapidly removed by oxidizing agents such as hydroxyl radicals and ozone. The latter reaction is termed ozonolysis and is an important source of Criegee intermediates (CIs), i.e., carbonyl oxides, that are implicated in enhancing the oxidizing capacity of the troposphere. These CIs aid in the formation of lower volatility compounds that typically condense to form secondary organic aerosols. CIs have attracted vast attention over the past two decades. Despite this, the effect of their substitution on the ground and excited state chemistries of CIs is not well studied. Here, we extend our knowledge obtained from prior studies on CIs by CF3 substitution. The resulting CF3CHOO molecule is a CI that can be formed from the ozonolysis of hydrofluoroolefins (HFOs). Our results show that the ground state unimolecular decay should be less reactive and thus more persistent in the atmosphere than the non-fluorinated analog. The excited state dynamics, however, are predicted to occur on an ultrafast timescale. The results are discussed in the context of the ways in which our study could advance synthetic chemistry, as well as processes relevant to the atmosphere.

Molecular dynamics evaluations of homogeneous condensation and thermophysical properties of (R-1234ze(E)+R-134a) binary blends

Environmental concerns demand prioritizing the development of eco-friendly refrigerants and prompting the replacement of conventional working fluids. The HFCs (hydrofluorocarbon) will be banned soon, and HFOs (hydrofluoroolefin) have been indicated as an alternative. In this study, numerous blends were attained by mixing two refrigerants, R-1234ze(E) and R-134a. Few blends are proposed as substitutes for high Global Warming Potential (GWP) fluids and are employed in refrigeration systems. The homogeneous condensation and thermophysical properties of nine binary blends of R-1234ze(E) + R-134a by varying composition with increment and decrement, respectively of 10% for each in a sequence were investigated using a molecular dynamics simulations scheme. The density, isobaric heat capacity, mean square displacement, internal potential energy and radial distribution function were investigated at constant pressure and different condensation temperatures (273.15 K to 328.15 K). The present study aims to check how the mass ratio of different refrigerants can affect mentioned properties. The current outcomes are compared, analyzed and discussed with earlier available simulation data for pure and mixtures of refrigerants and along with REFPROP data. The computed results show that Blend 4, with a 60.0+40.0% mass ratio composition and R-450A, has similar condensation behavior and thermophysical properties. The properties of Blend 5 with a composition 50.0+50.0% mass ratio are nearly equal to Blend 4 and R-450A. The R-450A has a good inclusive performance as a pure alternative refrigerant. The physical properties of pure R-1234ze(E), R-134a and its nine binary blends were investigated and these results may be helpful for new HFO refrigerants based on these blends.

Vapor-liquid equilibrium for the binary mixed refrigerant {R1234ze(E) + R1336mzz(E)} at temperatures from 283.15 K to 313.15 K

Growing concerns regarding energy and environmental issues have prompted the development of refrigerants focused on energy conservation and environmental protection. Mixed refrigerants incorporating fourth-generation hydrofluoroolefins (HFOs) represent a promising advancement. Notably, R1234ze(E) and R1336mzz(E) are representative examples of environmentally friendly refrigerants within the HFO category. In this study, a vapor–liquid equilibrium (VLE) experimental apparatus was constructed based on the liquid-phase cycling method, and the VLE data for eleven R1234ze(E) + R1336mzz(E) mixed refrigerants with varying proportions were measured within the temperature range of 283.15 ∼ 313.15 K. In addition, all the experimental data were correlated using two models: the Peng-Robinson (PR) equation of state combined with the van der Waals (vdW) mixing rule, and the PR equation of state combined with the Huron-Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient. The results indicate that R1234ze(E) + R1336mzz(E) mixed refrigerants do not exhibit azeotropic behavior within the studied temperature range. Furthermore, both the PR + vdW and PR + HV + NRTL models show good agreement with the experimental data, with the latter model demonstrating superior performance.

Projections of National-Gridded Emissions of Hydrofluoroolefins (HFOs) in China.

Hydrofluoroolefins (HFOs) are being used as substitutes for potent greenhouse gas hydrofluorocarbons (HFCs). However, the use and environmental impacts of HFOs are of great concern due to the rapid degradation of HFOs to produce persistent and phytotoxic trifluoroacetic acid (TFA). Here, we provide a comprehensive projection of HFO emissions in China during 2024-2060 for the first time. Under the Kigali Amendment to the Montreal Protocol, China's HFO emissions are estimated to increase from 1.7 (1.3-2.3) to 148.8 (111.4-185.4) kt in 2024-2060 with cumulative emissions of 2.8 (2.0-3.5) Gt, and cumulative reduced HFCs emissions are evaluated to be 5.4 Gt CO2-equivalent. High HFO emissions would be distributed mainly in the North China Plain and the eastern and coastal areas. HFO-1234yf (2,3,3,3-tetrafluoropropene) contributes most of HFO emissions with a cumulative emission of 1.7 Gt in 2024-2060, while the cumulative increment of TFA deposition from HFO-1234yf emissions would reach 0.4-1.0 Gt. The long-term national-gridded HFO emission inventories can provide scientific support for evaluating the environmental risks of HFOs and developing HFC phase-out pathways for addressing climate change.

Zeotropic mixtures R1234ze(Z)/acetone and R1234ze(Z)/isohexane as refrigerants in high temperature heat pumps: Influence of the accuracy in thermodynamic properties evaluations

High temperature heat pumps (HTHPs) represent an interesting option to upgrade waste heat up to 200 °C for industrial application. In order to achieve such high temperatures, suitable refrigerants are needed. In this paper, two zeotropic mixtures composed of a hydrofluoro-olefin (HFO) and a hydrocarbon, namely R1234ze(Z)/acetone and R1234ze(Z)/isohexane, were examined as the refrigerant for HTHP applications. The main objective of the present study is to determine the binary interaction parameters (BIPs) of the two zeotropic mixtures from experimentally-determined thermodynamic properties and analyze how HTHP performance assessment would change after tuning the BIPs. For R1234ze(Z)/acetone, after tuning the BIPs, the phase change temperature glide did not change that much. However, the composition corresponding to the highest temperature glide changed significantly. On the other hand, for R1234ze(Z)/isohexane, the phase change temperature glide changed significantly with tuned BIPs, while the composition for the maximum temperature glide was quite similar in the two cases. A thermodynamic optimization framework was used for simulation of the HTHP cycle. Simulation results using estimated BIPs showed that for R1234ze(Z)/acetone the optimum coefficient of performance (COP) was 3.95, while it slightly changed to 3.94 (around 0.25% change) after tuning the BIPs. However, the optimum composition of the mixture was quite different for the estimated and fitted BIPs. For R1234ze(Z)/isohexane the COP was 3.90 using estimated BIPs, while it changed to 3.83 (around 1.7% change) once the fitted BIPs were used. These results indicate the importance of tuning the BIPs for zeotropic mixtures and different impacts depending on the performance parameters analysed.