Azeotropic Refrigerant Research Articles

Theoretical study and experimental verification of the viscosities of azeotropic refrigerant R515B

One essential aspect of the studies on the refrigeration and heat pump technology is to search for new alternative working fluids. Meanwhile, the azeotropic mixtures of hydrofluorocarbons (HFCs)/hydrofluoroolefins (HFOs) have attracted researchers not only in fundamentals research field but also in the industry fields due to its good performance and applicability. Therefore, to promote application research, this study is focused on the characteristics of viscosity for azeotrope R515B, which is widely recognized and studied from the thermodynamic aspect. Hence, the high-pressure density and viscosity in liquid phase of R515B were measured with a vibrating-wire viscosimeter within the temperature range in 253 K to 363 K when pressure changes from 1 MPa to 12 MPa. The combined expended uncertainties with a confidence level of 0.95 (k = 2) of density and viscosity are 0.2 % and 2 %, respectively. In addition, a modified viscosity model is proposed with combining the parameterization method of thermodynamic equation of state (EoS) in previous work and the modified entropy variable as well as reduced viscosity reference term of residual entropy scaling (RES) theory. Furthermore, the systematical comparison results among this model and three benchmark viscosity models available illustrate that the RES model proposed in this research is robust and precise in a wide range of operation condition.

Ionic liquid fluoropolymer membranes for the separation of R-410A: Understanding the effect of ionic liquid on membrane characteristics and separation performance

Environmental legislation such as the American Innovation and Manufacturing Act will phase out today's generation of high-global warming hydrofluorocarbon refrigerants over the next two decades. Energy-efficient technologies are needed to separate these often azeotropic and complex mixtures. Membrane technology and extractive distillation with ionic liquids as entrainers have been individually developed for the separation of azeotropic refrigerant mixtures. This study provides details for the separation of R-410A through combining the benefits of glassy, amorphous polymers with ionic liquids to form ionic liquid polymer membranes. Two different classes of ionic liquid polymer membranes are considered: polyvinyl acetate composite membranes with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, and 1-hexyl-3-methylimidazolium chloride, and Hyflon AD 60 with 1-ethyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide. The membranes are characterized with FTIR, helium pycnometry, differential scanning calorimetry, and a high-pressure view-cell to characterize the effect of ionic liquid on polymer properties. The Hyflon AD 60 composite membranes were evaluated for the separation of R-410A through pure-gas permeability, selectivity, solubility, and diffusivity measurements, which show exceptional selectivity for separation of R-410A. Results provide insights on the effect of ionic liquid on the separation of R-410A and indicate that improved separation performance of glassy polymers can be achieved with the addition of ionic liquid.

Ionic Liquids for the Separation of Fluorocarbon Refrigerant Mixtures.

This review discusses the research being performed on ionic liquids for the separation of fluorocarbon refrigerant mixtures. Fluorocarbon refrigerants, invented in 1928 by Thomas Midgley Jr., are a unique class of working fluids that are used in a variety of applications including refrigeration. Fluorocarbon refrigerants can be categorized into four generations: chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, and hydrofluoroolefins. Each generation of refrigerants solved a key problem from the previous generation; however, each new generation has relied on more complex mixtures that are often zeotropic, near azeotropic, or azeotropic. The complexity of the refrigerants used and the fact that many refrigerants form azeotropes when mixed makes handling the refrigerants at end of life extremely difficult. Today, less than 3% of refrigerants that enter the market are recycled. This is due to a lack of technology in the refrigerant reclaim market that would allow for these complex, azeotropic refrigerant mixtures to be separated into their components in order to be effectively reused, recycled, and if needed repurposed. As the market for recovering and reclaiming refrigerants continues to grow, there is a strong need for separation technology. Ionic liquids show promise for separating azeotropic refrigerant mixtures as an entrainer in extractive distillation process. Ionic liquids have been investigated with refrigerants for this application since the early 2000s. This review will provide a comprehensive summary of the physical property measurements, equations of state modeling, molecular simulations, separation techniques, and unique materials unitizing ionic liquids for the development of an ionic-liquid-based separation process for azeotropic refrigerant mixtures.

Study of CHF3/CH2F2 Adsorption Separation in TIFSIX-2-Cu-i.

Hydrofluorocarbons (HFCs) have important applications in different industries; however, they are environmentally unfriendly due to their high global warming potential (GWP). Hence, reclamation of used hydrofluorocarbons via energy-efficient adsorption-based separation will greatly contribute to reducing their impact on the environment. In particular, the separation of azeotropic refrigerants remains challenging, such as typical mixtures of CH2F2 (HFC-23) and CHF3 (HFC-32), due to a lack of adsorptive mechanisms. Metal-organic frameworks (MOFs) can provide a promising solution for the separation of CHF3-CH2F2 mixtures. In this study, the adsorption mechanism of CHF3-CH2F2 mixtures in TIFSIX-2-Cu-i was revealed at the microscopic level by combining static pure-component adsorption experiments, molecular simulations, and density-functional theory (DFT) calculations. The adsorption separation selectivity of CH2F2/CHF3 in TIFSIX-2-Cu-i is 3.17 at 3 bar under 308 K. The existence of similar TiF62- binding sites for CH2F2 or CHF3 was revealed in TIFSIX-2-Cu-i. Interactions between the fluorine atom of the framework and the hydrogen atom of the guest molecule were found to be responsible for determining the high adsorption separation selectivity of CH2F2/CHF3. This exploration is important for the design of highly selective adsorbents for the separation of azeotropic refrigerants.

Separation of Azeotropic Refrigerant Mixtures: R-450A, R-456A, R-515B, and R-516A Using Phosphonium- and Imidazolium-Based Ionic Liquids

Separation of Azeotropic Refrigerant Mixtures: R-450A, R-456A, R-515B, and R-516A Using Phosphonium- and Imidazolium-Based Ionic Liquids

An experimental investigation of nucleate boiling performance for low-GWP azeotropic refrigerant R513A on a smooth tube

In the present study, an experimental investigation is conducted to study the nucleate boiling characteristics on a smooth tube having a low-GWP azeotropic refrigerant, R513A. The heat flux ranges from 5 to 90 kW/m2, and saturation temperatures are 0, 6, 10, 16, and 22 °C, respectively. The performance of R513A is compared against that of R134a. The performance is in terms of heat transfer coefficient (HTC). HTCs normally increased with the rise of heat flux and saturation temperature. However, the HTCs of R513A exceed those of R134a by approximately 20–25 %. Additionally, comparative analysis of the test data and some existing correlations are made. The compared correlations include three correlations based on reduced pressure (Cooper, Ribatski and Jabardo, and Jung), as well as two correlations based on thermophysical properties. It is found that the Jung correlation gives the best overall predictive ability against the R513A data with a deviation ranging from 5 % to 10 %.

Azeotropic Refrigerant Mixture R-513A Separation Using Extractive Distillation with Ionic Liquids Entrainers

Azeotropic Refrigerant Mixture R-513A Separation Using Extractive Distillation with Ionic Liquids Entrainers

Molecular dynamics investigation on the interaction of nitrile-based ionic liquids in the separation of azeotropic refrigerant R-513A

The reclamation of mixed refrigerants stands as a potent measure to substantially mitigate the emission of fluorinated gases (F-gases). In the separation of the azeotropic refrigerant R-513A (comprising 56 wt% R-1234yf, 2,3,3,3-Tetrafluoropropene, and 44 wt% R-134a, 1,1,1,2-Tetrafluoroethane), the extractive distillation process using ionic liquids (ILs) was employed. The molecular structure of nitrile-based ILs ([C4C1im][SCN], [C4C1im][N(CN)2], [C4C1im][C(CN)3], [C4C1im][B(CN)4]) exerts a regular impact on the solubility of refrigerants, thereby necessitating molecular dynamics simulation to ascertain the law of refrigerant solubility in ILs concurrent with the augmentation in the number of –CN in the anion. Additionally, an analysis was conducted to elucidate the mechanism underlying the high selectivity of nitrile-based ILs. The results revealed pronounced interactions between R-1234yf and R-134a, predominantly occurring between carbon atoms (-CF3 groups in R-134a and R-1234yf), and chiefly van der Waals interactions. An enhancement in the number of –CN in anion led to the fortification of the van der Waals interaction between R-134a/R-1234yf and the anion. The stronger nonbonding interaction energy between R-134a and the anion, as well as the higher radial distribution function (RDF) peak height between R-134a and the anion, signified a more robust interaction between R-134a and the anion compared to R-1234yf and the anion. Concurrently, the variance in the RDFs in the anion-C atom (-CH2F group in R-134a and -CF group in R-1234yf) revealed the selectivity of the four ILs to R-134a and R-1234yf. Among the four anions, [B(CN)4]− exhibited the most interaction sites with R-134a. This investigation contributes significantly to comprehending the interaction mechanism of azeotropic refrigerants and the interaction mechanism between refrigerants and nitrile-based ILs.

Flow boiling heat transfer coefficient and pressure drop of R448A inside various multiport tubes: An experimental investigation and correlation assessment

R448A, a safety class A1 a-zeotropic refrigerant blend with a GWP of 1390, is considered an efficient and environmentally friendly substitute for R404A in direct-expansion commercial refrigeration systems. Herein, we experimentally investigate the flow boiling heat transfer and pressure drop of R448A inside a multiport mini-channel tube. The experimental ranges of mass flux and heat flux are 100–500 kg/m2s and 3–15 kW/m2, respectively, and they cover the entire quality range at three different saturation temperatures of 3, 6, and 10°C. Three different test tubes are utilized in this study to evaluate the effect of tube geometry on the heat transfer, and their diameters range from 0.831 to 1.14 mm. The results show that mass flux has favorable effects on the heat transfer coefficient and pressure drop, while heat flux has a favorable effect on the heat transfer coefficient at low mass fluxes. As the saturation temperature decreases when the mass flux is high, the heat transfer coefficient and pressure drop increase. The tube with largest perimeter but the smallest hydraulic diameter has the highest heat transfer coefficient under the low mass flux condition. Heat transfer coefficient and pressure drop experimental data were compared with the models in literature, and the results of our statistical assessment indicate that the pure fluid model modified to account for the mixture effect produces the best results. Meanwhile, most pressure drop models produce reasonably good predictions. Additionally, a new correlation is proposed to predict the heat transfer coefficient in practical applications.

Multipolar SAFT-VR Mie Equation of State: Predictions of Phase Equilibria in Refrigerant Systems with No Binary Interaction Parameter.

An extension of the SAFT-VR Mie equation of state is proposed to predict the properties of multipolar fluids. The new model, referred to as multipolar M-SAFT-VR Mie, incorporates the general multipolar term developed by Gubbins and co-workers, which accounts for dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole interactions. A modification of the third order terms in the perturbation theory results in an accurate description of the simulation data for multipolar Lennard-Jones fluids. Both the M-SAFT-VR Mie and polar soft-SAFT models are extended to account for polarizability, and a good agreement is obtained with molecular simulation data. The M-SAFT-VR Mie model is applied to refrigerant systems, and it is found that including both dipole and quadrupole moments in molecular models leads to more accurate results than using only a dipole moment. The new model provides excellent predictions of the vapor-liquid equilibria of zeotropic and azeotropic refrigerant mixtures without the need for binary interaction parameters, making it a valuable tool for formulating low-GWP working fluids.

Comparative Study on Boiling Heat Transfer Characteristics and Performance of Low-Temperature Heating System of R744 and Its Azeotropic Refrigerant

R744 is the most competitive and ideal natural refrigerant when flammability and toxicity are strictly limited. However, there are still some problems when it is applied to a heating system. For example, the discharge pressure of the system exceeds 10 MPa, it increases the cost of the system, and the cycle efficiency is also low. To solve these problems, this paper proposes to replace R744 by mixing R744 and ethane at a ratio of (77.6/22.4) to form an azeotropic refrigerant. At present, there is little research on R744 azeotropic refrigerant. Therefore, this paper first establishes the CFD model and compiles the UDF program to focus on flow boiling heat transfer characteristics, and then, it analyzes the performance of R744 and its azeotropic refrigerant in a low-temperature heating system. The results show that the heat transfer coefficient of R744 and its azeotropic refrigerant decreases with an increase in mass flux and increases with an increase in heat flux and saturation temperature; the heat transfer coefficient of azeotropic refrigerant is greater than R744; and there is no dryness under the same conditions. Under a given operating condition, there is a critical point that makes the performance of azeotropic refrigerant better than R744, and this critical point is related to the outlet temperature of a gas cooler, and the system discharge temperature of azeotropic refrigerant is significantly lower than that of R744. In conclusion, azeotropic refrigerant has certain advantages in heat transfer and system performance compared with R744, which will also play an important role in promoting the replacement of refrigerant in the future.

Regression Model of Dynamic Pulse Instabilities during Condensation of Zeotropic and Azeotropic Refrigerant Mixtures R404A, R448A and R507A in Minichannels

This paper presents experimental research and mathematical modeling data concerning the impact of unit dynamic instabilities on the phase-transition condensation processes of the zeotropic mixtures R404A and R448A and azeotropic R507A refrigerants in pipe minichannels. The R507 refrigerant is currently used as a temporary substitute for R404A, whereas R448A is a sustainable prospective substitute for R404A. The study presents experimental testing data for the condensation processes of these refrigerants in pipe minichannels and a proposal for the use of dimensional analysis, including the Π-Buckingham theorem, to determine the regression relationship explaining the propagation of unit dynamic instabilities. Based on the experimental studies performed, regression computational models were developed and showed satisfactory agreement in the range of 20% to 25%. They give the possibility to identify, in a utilitarian, way the speed of propagation of temperature and pressure instabilities during the liquefaction of refrigerants. The study was carried out on pipe minichannels with an internal diameter of di = 3.3, 2.3, 1.92, 1.44 and 1.40 mm.

Interfacial properties of fluorinated (F)-gases in azeotropic condition

The interfacial behavior in refrigerant mixtures has a major impact on heat transfer coefficients during the vaporization and condensation stages. Therefore it is appropriate to have robust models to predict their properties. In this work, molecular dynamic simulations together with density gradient theory combined with the statistical associating fluid theory of variable range employing a Mie potential (SAFT-VR-Mie) have been employed to model and understand the interfacial behavior in systems of azeotropic refrigerant mixtures of fluorinated gases (R32, R125, R134a, R143a, and R152a) blended with propane (R290). It is demonstrated that despite the high-non ideal behavior in these mixtures, both approaches are capable of reproducing the minimum in surface tension (aneotropy) as a function of composition and temperature for the considered mixtures. It is concluded that the minimum occurs close but not equal to the azeotropic condition. Besides, it is also observed that the azeotropic condition acts as a switching point, in which R290 starts to accumulate at the interface positively. In contrast, in all mixtures, mixtures F-gases do not exhibit surface activity. Finally, the involving azeotropic condition was reduced, without loss of rigor, to a simpler problem that involves the VLE of a pseudo-pure component, in which molecular properties are characterized to be used in molecular simulations.

Comparative Study on Boiling Heat Transfer Characteristics and Performance of Low Temperature Heating System of R744 and its Azeotropic Refrigerant

Comparative Study on Boiling Heat Transfer Characteristics and Performance of Low Temperature Heating System of R744 and its Azeotropic Refrigerant

Prediction of ternary azeotropic refrigerants containing ammonia

Developing azeotropic refrigerants based on ammonia is a promising way to achieve better refrigeration performance and less refrigerant charge than using ammonia alone. In this paper, ammonia-based, homogenous ternary azeotropic refrigerants were predicted. The Peng-Robinson equation of state was combined with the non-random two-liquids (NRTL) to represent the vapor-liquid equilibrium (VLE) behavior of binary and ternary mixtures. The non-randomness binary interaction parameter α in NRTL model has a significant influence on the VLE description of the ammonia mixtures, while such influence is commonly weak in hydrocarbon or hydrofluorocarbon mixtures at α from 0.2 to 0.47. Empirically, α = 0.2 is more suitable for ammonia mixtures rather than the conventional default value 0.3. The azeotropic loci of the mixtures were determined by the extreme pressure method. Ten ternary systems were predicted, of which three maximum-point azeotropes were found, namely ammonia + n -butane + pentafluoroethane /1,1-difluoroethane /2, 3, 3, 3 - tetrafluoroprop-1-ene. The ternary azeotropes predicted are thought to be promising substitute refrigerants.

Air conditioning cycle simulations using a ultrahigh-speed centrifugal compressor for electric vehicle applications

Electric vehicles (EVs) are an increasingly popular option to decrease global greenhouse emissions in the transportation sector. The largest limiting factor is their range, significantly decreased by the cooling load required. In conjunction with the shift to incorporating low-Global Warming Potential (GWP) refrigerants in cooling systems, it is critical to reexamine the design of traditional air conditioning (AC) systems. To this end, a model of a cooling system for an EV was created, while incorporating an ultrahigh-speed miniature centrifugal compressor, allowing for the performance comparison of multiple refrigerants. From these simulations, a centrifugal compression system using HFC-134a provided sufficient cooling capacity for the modeled vehicle (13.07 kW) with lower input power requirements (2.05 kW) than a commercial EV AC system. However, this requires improved heat exchanger efficiencies. A straightforward system design may be attainable with lower operating pressures utilizing the low-GWP HFO-1336mzz(Z) while achieving a nearly equivalent cooling capacity (12.39 kW) at reduced power requirements (1.86 kW). Performance and safety tradeoffs were examined for a variety of refrigerants and azeotropic mixtures. The use of azeotropic refrigerants increased the cooling capacity and energy efficiency compared with the individual components, but with the tradeoff of higher pressure and compressor exit temperatures. Overall, this effort provides specified conditions for EVs while being among the first to demonstrate the potential of low-GWP and low-Ozone Depletion Potential refrigerants in AC systems utilizing ultrahigh-speed centrifugal compressors.

The Data Mining Technique Using RapidMiner Software for New Zeotropic Refrigerant

This research presents the development of environmentally-friendly and energy efficient refrigerant for medium temperature refrigeration systems that new azeotropic refrigerant mixture of hydrofluorocarbons and hydrocarbon that can retrofit in the refrigeration system using R404A. The medium back pressure refrigeration testing standard that follow CAN/ANSI/AHRI540 standard air-conditioning, heating, and refrigeration institute (AHRI) and The properties of refrigerants and refrigeration simulation system that used national institute of standards and technology (NIST) reference fluid thermodynamic and transport properties database (REFPROP) software and NIST vapor compression cycle model accounting for refrigerant thermodynamic and transport properties (CYCLE_D-HX) software. The methodology uses decision tree function in datamining by rapid minor software that first of KDnuggets annual software poll that showed new azeotropic refrigerant mixture had cooling capacity, refrigerant effect, GWP and boiling point were lower than R404A but work and pressure for medium temperature refrigeration system of azeotropic refrigerant mixture were higher than R404A. The artificial intelligence (AI) by data mining technic can predictive environmentally-friendly and energy efficient refrigerant for medium temperature refrigeration. The result of refrigerant mixed by R134A, R32, R125 and R1270 and is consistent with the evolution of fourth-generation refrigerants that contain a mixture of HFCs and HCs which are required to produce a low-GWP, zero-ozone-depletion-potential (ODP), high-capacity, low-operating-pressure, and nontoxic refrigerant.

Study on environmentally friendly refrigerant R13I1/R152a as an alternative for R134a in automotive air conditioning system

Abstract Aiming at solving the problem of high global warming potential of R134a, a new mixed refrigerant R13I1/R152a (molar fraction ratio of 35:65) with no ozone depletion potential and low global warming potential was proposed as a substitute for R134a in automotive air conditioning. The computational models for the thermodynamic properties of R13I1/R152a were established by using the PR equation of state combined with the vdW mixing rule. Based on these models, the cycle performance of this working fluid was calculated, which was also compared with that of R134a and R1234yf under the different operating conditions. The results show that R13I1/R152a is a near azeotropic refrigerant whose temperature glide is approximately 0, and the saturated vapor pressure curve of which is equivalent to that of R134a. Moreover, compared to R134a, R13I1/R152a has an average 5.7% improvement in coefficient of performance as well as similar volumetric cooling capacity. The average coefficient of performance and volumetric cooling capacity of R13I1/R152a are significantly higher than those of R1234yf by 13.8% and 12.0%, respectively. However, the average discharge temperature of R13I1/R152a is approximately 13.3 K higher than that of R134a, but it is also within reasonable limits. Hence, the application of the proposed refrigerant R13I1/R152a in automotive air conditioning system is technically feasible.

Comparison of different adsorption pairs based on zeotropic and azeotropic mixture refrigerants for solar adsorption ice maker.

One of the important ways to the efficiently use of low-grade thermal energy is the adsorption refrigeration technology. However, it has some drawbacks such as low specific cooling power and coefficient of performance, especially under using the conventional adsorption pairs. Therefore, new adsorption pairs are tested in solar adsorption ice-maker and compared with other conventional pairs data from open literature to find the tendency of improving the solar adsorption ice-maker performance. The experimental test rig has been built in Upper Egypt in Qena City. Four different new adsorption pairs of granular activated carbon/R-410A, granular activated carbon/R-511A, Maxsorb III/R-410A, and Maxsorb III/R-511A are used. It is demonstrated that Maxsorb III/R-511A pair based solar adsorption ice-maker produced the highest values for specific cooling power, coefficient of performance, and ice production per 1kg of adsorbent of approximately 226.7W/kgads, 0.197, and 1.96kg/kgads, respectively. While granular activated carbon/R-410A based solar adsorption ice-maker produced the lowest values of ice production per 1kg of adsorbent and coefficient of performance of 1.38kg/kgads and 0.104, respectively. Moreover, it can be concluded that the tested pairs are feasible to be used in solar adsorption ice-maker systems, especially in such hot climate of Upper Egypt for food and vaccine preservation and storage.

Development of Environmentally Friendly and Energy Efficient Refrigerants for Refrigeration Systems

This paper presents the improvement of eco-friendly and power consumption saving refrigerants for refrigeration systems. The novel azeotropic refrigerant mixtures of HFCs and HCs can replace refrigeration systems, and using the R134, R32, R125, and R1270 refrigerants in several compositions found using the decision tree function of the RapidMiner software (which came first in the KDnuggets annual software poll). All refrigerant results are mixed of POE, which is A1 classification refrigerant, non-flammable, and innocuous refrigerant, and using REFPROP software and CYCLE_D-HX software are under the CAN/ANSI/AHRI540 standards. The boiling point of the new refrigerant mix R-No.595 is 4.58%, lower than that of R404A, with a higher refrigerant effect and 50.34% lower GWP value than R404A. The proposed mix R-No.595 can be operated in hot environmental country and has high critical temperature and heat-rejection effects, due to the presence of R32 and R1270. The COPc of R463A is 13.49%, higher than R404A in freeze condition. The novel refrigerant mixes provide alternate refrigerant options mixed of 1% R1270, and which are related with the development of current refrigerants, containing a compose of HFOs and eco refrigerants for producing low-GWP, zero ODP, high-refrigerant effect, low-operating pressure, and innocuous refrigerants.