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The current small passenger car vapor compression refrigeration systems use high global warming potential (GWP) refrigerants causing the greenhouse gas effect. In the present work, the low GWP of two pure refrigerants, R1234yf and R1234ze (E), and 16 blends of R134a, R1234yf, and R1234ze (E) are analyzed numerically. The experiments were conducted with R134a refrigerant to validate the numerical results. The experiments were conducted at the compressor speed of 600–1500 rpm and the condensing air at 30–40°C, relative humidity of 85%, and velocity of 1–3 m/s. The simulation and experimental results for R134a are deviated by a minimum of 10% and a maximum of 15%. It is found that the latent heat of vaporization of the two refrigerant mixtures with 80% R134a–20% R1234yf and the three refrigerant blends of 50% R134a–10% R1234yf–40% R1234ze (E) are the highest among 16 combinations. The other blends show a moderate difference of latent heat with R134a, but for maximum cooling capacity, the blends with 80% R134a–20% R1234yf and 50% R134a–10% R1234yf–40% R1234ze (E) are found to be more suitable for practical applications. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The global critical issue in energy scarcity should be appropriately solved to realize a sustainable society. Effective use of Rankine cycle is one possible way since it provides most of worldwide electricity production. In this paper, theoretical analysis model of organic working fluids R717, R134a, R1234yf, R290, R245fa and R1233zd in Rankine cycle for maximum power generation in optimization operation using low-temperature heat sources are proposed and studied for development next generation green and zero-carbon energy generation system to promote the race to zero. Results show that temperatures of warm and cold water at inlet, mass flow rate of the warm water and performance of the evaporator play a key role to obtain the theoretical optimization operation conditions for maximum power generation. In the case of same initial conditions of temperatures of warm water (85°C) and cold water (15°C) at inlet, mass flow rate of the warm water (10 kg/s) and performance of the evaporator (100 kW/K), R717 has the best performance in terms of the maximum power output 56.0 kW with thermal efficiency of 8.6%, and the next is the R1233zd (54.4 kW, 8.3%), R245fa (54.0 kW, 8.2%), R134a (52.8 kW, 7.9%), R290 (52.7 kW, 7.9%), and R1234yf (51.7 kW, 7.7%). Here, it should be noticed that other optimization conditions are almost the same (mass flow rate of the cold water 9.1–9.2 kg/s; performance of the condenser 91∼92 kW/K) to get their maximum power output of ORC. In addition, it also known that low-GWP R1233zd (GWP: 1) can deserve the best option to replace R245fa (GWP: 950) and R1234yf (GWP: 4) also can replace r134a (GWP: 1430) since their optimization operation conditions are almost same.

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of a new mixed refrigerant R1234yf/R13I1 with a mass ratio of 90/10 under basic refrigeration cycle and refrigeration cycle with internal heat exchanger is calculated in comparison with the performance of R134a under basic refrigeration cycle at different condensation temperature and evaporation temperature. The results show that R1234yf/R13I1 is virtually non-flammable with global warming potential of less than 4. Under basic refrigeration cycle, the compressor power consumption, cooling capacity and COP of R1234yf/R13I1 are lower than these of R134a by about 4.5%, 9.5%, and 7.5%, respectively. Under refrigeration cycle with internal heat exchanger, the compressor power consumption, cooling capacity, and COP of R1234yf/R13I1 are lower than these of R134a by about 2%, 4.5%, and 3%, respectively. The R1234yf/R13I1 is a beneficial refrigerant of replacing R134a in vapor compression system. [ABSTRACT FROM AUTHOR]

Nanolubricants can improve the tribological properties for application in automotive systems. By reducing the friction rate of the internal components with nanolubricants, the service life of a compressor used in automotive air conditioning (AAC) can be extended. The investigation aims to determine the optimal volume concentration of nanolubricants for achieving the highest performance in tribological properties. Al2O3 nanoparticles dispersed in a polyalkylene glycol (PAG ND12) base at volume concentrations of 0.01%, 0.03%, and 0.05% were investigated to improve the lubrication system in the AAC compressor. The stability investigations were carried out by comparing absorbance conditions using a UV-Vis Spectrophotometer at each volume concentration for 210 days. Koehler's four-ball tribometer was used to measure coefficient of friction (COF) and friction torque at a load of 40.0 kg and a speed of 1200 rpm. The stability study of nanolubricant yielded average absorbance values of 0.752, 0.755, and 0.684, respectively. The average COF values of the nanolubricants of 0.01%, 0.03%, and 0.05% were 0.104, 0.078, and 0.117, while the pure lubricant was 0.095. Further investigation on friction torque resulted in a decrease in the pure lubricant of 0.064%, and for nanolubricant Al2O3/PAG ND12, a decrease of 0.087%, 0.057%, and 0.092%, respectively. The results indicated that a concentration of 0.03% produced the greatest reduction in COF and torque, namely 0.0078% and 0.0578%, correspondingly. Therefore, it is recommended to use Al2O3/PAG ND12 nanolubricant at a volume concentration of 0.03% because it is the most optimal in terms of stability and has the highest COF and frictional torque reduction. [ABSTRACT FROM AUTHOR]

In this article, in order to reduce the climate hazards caused by global warming, a new environmentally friendly mixed refrigerant, R1234yf/R125 (with a mass ratio of 95:5), is introduced. Alongside R1234yf, the article conducts theoretical research to assess the feasibility of substituting R134a in vapor compression systems. The results show that coefficient of performance (COP) and compressor discharge temperatures of R1234yf and R1234yf/R125 are ~5.5% and 11°C lower than those of R134a, respectively. The volumetric cooling capacity of R1234yf is on average 8% smaller than that of R134a. The volumetric cooling capacity of R1234yf/R125 is similar to that of R134a, making it highly suitable for direct charging. R1234yf/R125 is basically nonflammable, with a minimal temperature glide, ozone depletion potential of 0 and a global warming potential of 144. It adheres to F-gas regulations and serves as an outstanding replacement for R134a. [ABSTRACT FROM AUTHOR]

A major portion of the worldwide emissions arise from mobile air-conditioning systems with hydrofluorocarbon refrigerant as working substance and which is one of major cause for the greenhouse effect. R134a refrigerant having GWP of 1400 has been extensively used in car air conditioning. To reduce greenhouse gas emissions, the current R134a refrigerant must be phase out as per Kigali Amendment. The present study deals with cooling load calculation of car model by heat balance method as per ASHRAE standard using local climate condition. Further, thermodynamic analysis of R1234yf as an alternate refrigerant to R134a has been carried out for automobile air conditioning system. The required properties of refrigerants are extracted from Engineering Equation Software. The thermodynamic analysis is carried out to study the effect of operating parameters viz. condensing temperature, evaporating temperature, degree of superheating and degree of subcooling on COP, EDR, exergy efficiency and entropy generation. The previous literature reports mainly focus on separate study of either cooling load calculation or energy analysis or exergy analysis of R1234yf and R134a for automobile air conditioning system, while this paper presents the comprehensive study of new low GWP R1234yf as an alternate refrigerant to R134a in automobile air conditioning system with cooling load calculation including the concept of energy, entropy and exergy analysis. The percentage difference in COP between R134a and R1234yf system varies from 2.44 % to 4.78 % while percentage difference in EDR varies from 6.79 % to 2.87 % when evaporating temperature varied from -10 °C to 10 °C. With 12 °C of superheating at compressor inlet, the COP of R134a is 3.9 whereas COP of R1234yf is 3.75, which makes 3.85 % lower than that of R134a. The R1234yf has 4.78 % lower value of exergy efficiency as compared to that of R134a at evaporating temperature of -10 °C and it is found that maximum exergy destruction takes place in compressor. [ABSTRACT FROM AUTHOR]

R134a, a vehicle refrigerant used in the vehicle heat pump system, is regulated according to the Montreal Protocol. Refrigerants such as R1234yf, R744, and R290 in vehicle heat pump systems are being investigated to identify their alternatives. Because developing a new system exclusively for new refrigerants is costly, an empirical test was conducted on the R1234yf refrigerant in a heat pump system designed for the R134a refrigerant in an actual vehicle system. The heating, cooling, and battery-cooling modes were tested for the amount of refrigerant charge, and operability tests were conducted for the compressor load; heating, ventilation, air conditioning (HVAC) air flow rate; coolant temperature; and flow rate of each mode. The optimal refrigerant charge in heating mode was 0.7 kg, and the optimal refrigerant charge in the cooling and battery-cooling modes was 0.9 kg. To yield the highest coefficient of performance of the system, the compressor load was 50%, the HVAC fan was 12 V, and the coolant flow rate was 10 LPM. The most efficient system operation was possible at a coolant temperature of 30 °C in the cooling and heating modes and at 20 °C in battery-cooling mode. [ABSTRACT FROM AUTHOR]

The micro- and nanostructures, chemical composition, and wettability of titanium surfaces are essential for dental implants' osseointegration. Combining hydrophilicity and nanostructure has been shown to improve the cell response and to shorten the healing time. This study aimed to investigate the biological response to different wettability levels and nanotopographical modifications in aged and non-aged titanium surfaces. By plasma etching titanium surfaces with the fluorine gas 2,3,3,3-tetrafluoropropene (R1234yF), additional nanostructures were created on the sample surfaces. Furthermore, this treatment resulted in sustained superhydrophilicity and fluoride accumulation. We examined the effect of various nanostructuring processes and aging using scanning electron microscopy, roughness analyses, and wettability measurement. In addition, all the surface modifications were tested for their effects on fibroblast adhesion, proliferation, and viability as well as osteoblast differentiation. Our study indicates that the plasma etching, with 2,3,3,3-tetrafluoropropene, of the machined and SLA surface neither favored nor had an adverse effect on the biological response of the SAOS-2 osteoblast cell line. Although the fluorine-plasma-etched surfaces demonstrated improved fibroblast cell viability, they did not lead to improved early osseointegration. It is still unclear which surface properties mainly influence fibroblast and osteoblast adhesion. Further physiochemical aspects, such as electrostatic interaction and surface tension, are crucial to be analyzed along with wettability and roughness. [ABSTRACT FROM AUTHOR]

• Performance of an AAC system was investigated for different types of compressors and refrigerants. • The COP of the R1234yf system with VCC and FCC is about 13.6% and 20.1% lower than the R134a one, respectively. • The exergy destroyed in the system with VCC is 1.7%... 52.7% lower than that with FCC. • The exergy destroyed in the evaporator and condenser for R1234yf is less than that for R134a. In this study, the performance of R1234yf as an alternative to R134a has been experimentally investigated in an experimental automobile air conditioning (AAC) system with variable (VCC) and fixed (FCC) capacity compressors. The AAC system was equipped with original components and instruments for mechanical measurements. The experiments were conducted for both types of compressors and refrigerants at various compressor speeds, air temperatures entering the evaporator and condenser and air speeds passing over them. The performance parameters of the AAC system have been evaluated by performing energy and exergy analysis based on the experimental data, and the results were presented in the form of comparative graphics. The experimental results show that the VCC compressor limits the refrigerant flow rate when the capacity control system is activated due to the decrease in the evaporator and condenser air inlet temperatures and the increase in the compressor speed. It was found that the coefficients of performance (COPs) of the R1234yf AAC system with VCC and FCC were approximately 13.6% and 20.1% lower than those of the R134a system with VCC and FCC, respectively. For both refrigerants, in the AAC system with VCC, the total exergy destruction rate per unit cooling capacity was 18.2% − 47.5% lower compared to the system with FCC. The R1234yf AAC system experiences lower exergy destruction in the evaporator and condenser compared to the R134a system, while it practices higher exergy destruction in the compressor and expansion device in comparison to the R134a system [ABSTRACT FROM AUTHOR]

• Energy, exergy and multi-objective optimization are performed for vortex tube integrated single-stage vapour compression refrigeration cycle (VTC). • The parametric investigation is done to assess the thermodynamic performance of VTC. • The cooling capacity of VTC is found to be 13.19% – 49.73% higher than that of VCR. • The maximum COP and exergetic efficiency of VTC are higher than those of VCR. • The evaporator temperature is the most influential input parameter in multi-objective optimization. This paper evaluates the thermodynamic performance of a vortex tube integrated single-stage vapour compression refrigeration cycle (VTC) in a subcritical region. The thermodynamic evaluation consists of an energy and exergy analyses for VTC in order to determine the effect of various design and operating parameters on its performance. Moreover, the results of VTC are compared with those of a simple vapour compression refrigeration cycle (i.e., VCR) for the considered range of evaporator and condenser temperatures using R1234yf as a refrigerant. The analysis reveals that the cooling capacity of VTC is 14.53% – 49.73% higher than that of VCR for the considered range of condenser temperature. Also, the maximum COP of VTC is 5.59% – 27.32% higher than that of VCR. The exergetic efficiency of VTC is 5.62% – 27.33% higher than that of VCR. A multi-objective optimization using a genetic algorithm has been conducted, which suggests that the evaporator temperature is the major decisive parameter to find the suitability of various applications of the system based on VTC. [ABSTRACT FROM AUTHOR]

Low global warming potential hydrofluoroolefin-1234yf (R1234yf) is an alternative green refrigerant for the automotive air conditioning (AAC) system to replace the existing R134a refrigerant. However, the low energy efficiency of the AAC system using R1234yf has been a significant obstacle to its wider use. This paper describes using Al2O3–SiO2/DEC PAG nanolubricant to enhance the performance of the AAC-R1234yf system. The hybrid nanolubricant was created by a two-step preparation process. The experiment was undertaken at volume concentrations up to 0.05% and under various operating conditions. The stability test shows that the hybrid nanolubricant remained in superior stability after 6 months, with minimum particle aggregation and sedimentation. The AAC-Al2O3–SiO2/DEC PAG system achieved the best performance at 0.03% volume concentration with an average increment of 12.01%. This outcome was contributed by the increase of the AAC evaporator's heat absorb value by 2.8% and the reduction of the compressor work with an average decrease of 7.7%. In conclusion, a 0.03% volume concentration of Al2O3–SiO2/DEC PAG nanolubricant in the AAC compressor was recommended for optimum system performance and energy saving. [ABSTRACT FROM AUTHOR]

• Five C O2 blends have been identified, attempting non-flammability and GWP below 150. A theoretical assessment was performed varying the mixture's mass fraction and the environmental temperature. • At optimum conditions, the mass fraction of the C O2 -based blends has been optimized. • Binary mixtures C O2 /R32 and C O2 /R1270 report the best COP improvements with +21.4% and +8.7%, respectively. The extensive use of CO 2 in commercial refrigeration system has grown in the last two decade thanks to the development of new components and configurations that allows working in transcritical conditions efficiently. However, using these arrangements increases the cost and complexity of the refrigerating plant, making it challenging to implement them in medium or low-capacity systems. As an alternative, CO 2 -based binary mixtures report attractive improvements that allow for enhancing the COP of the system by minimising its complexity and maintaining the safety and environmental conditions of CO 2. This manuscript analyses five binary mixtures of CO 2 with the refrigerants R32, R152a, R1234yf, R1234ze(E) and R1270, determining the optimal mixture composition for maximising the COP of a CO 2 transcritical refrigeration plant in a wide range of environmental temperatures (0 to 40°C). Fixing the operating conditions for a medium-temperature application, the binary mixtures of C O2 /R32 (81/19% in mass) and CO 2 /R1270 (92.5/7.5% in mass) reported the best COP enhancements results with increments up to +21.4% and +8.7%, respectively, at high environmental temperatures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The inerting mechanism of the new flame retardants to flammable gases was investigated theoretically. All calculations were performed at the level of M06-2X/6-311 + G(d,p) using the density function method. Five different reaction pathways of traditional flame retardant group CF3 and 2,3,3,3-tetrafluoropropene (R1234yf) were calculated. Then, three novel flame retardant groups (BF2, BCl2 and BI2) for R1234yf were compared under the same reaction path. The results showed that the reaction energy barrier of the novel flame retardant groups was smaller than that of CF3, and the heat release was larger. It revealed that the flame retardant effect of the novel flame retardant groups is better than that of the traditional flame retardant group CF3. Furthermore, the deep discussions were made to the reconstruction of flame retardant molecules, which drew a material system map for the new flame retardant groups. Based on the analysis of environmental protection, flammability and thermophysical properties, new environment-friendly flame retardants suitable for different application fields can be obtained. [ABSTRACT FROM AUTHOR]

In this paper, an experimental study of R1234yf replacing R22 in window air conditioning was carried out. The optimum types of capillary tubes and the charge amount were obtained, and the system performance of the window air conditioning charged with R1234yf was tested in an air conditioner performance teat facility under nominal and high-temperature conditions. The results revealed that the cooling capacity and coefficient of performance (COP) of the air conditioner charged with R1234yf were 28.5% and 11.1%, respectively, under nominal conditions, which were lower than that of R22. Under high-temperature conditions, the cooling capacity of R1234yf was still lower than that of R22, but the COP was slightly higher. This suggests that R1234yf may be a suitable substitution for R22 in high-temperature environment. [ABSTRACT FROM AUTHOR]

• A refrigerant composition estimation model is evaluated based on the measured absorption characteristics of pure refrigerant and refrigerant mixtures. • Difluoromethane (R32) and 2,3,3,3-tetrafluoropropene (R1234yf) have distinctive absorbance spectra in the near-infrared region. • The absorption characteristics of liquid phase are relatively stable in the near-infrared region under temperature and pressure conditions. • Spectroscopic measurements shows good agreement between the measured and estimated values performed at the composition ratios of R32 : R1234yf = 30 : 70, 50 : 50, 70 : 30. Near-infrared absorption spectra of difluoromethane (R32) and 2,3,3,3-tetrafluoropropene (R1234yf) were experimentally measured for superheated gas and subcooled liquid under different temperature and pressure conditions. Molar attenuation coefficients at wavelengths of 1.59, 1.64, 1.70 and 1.78 μm were obtained using 1.5 μm wavelength data as a reference spectrum. Attenuation coefficient of the gas phase R32 refrigerant showed significant variation depending on the operating conditions, where liquid phase showed relatively constant absorption characteristics at different pressures and temperatures. Furthermore, the attenuation coefficients were distinctive between R32 and R1234yf and absorption peaks and intensities were identical. The estimation model of absorption characteristic for refrigerant mixture was then constructed using the liquid phase spectra of the pure refrigerants at each wavelength with validation using the experiment data of upward flow with circulation compositions of R32 : R1234yf = 30 : 70, 50 : 50 and 70 : 30 mass%. The estimated data qualitatively showed good agreement with the measured spectra in point of dependency on composition ratio. However, up to 15% deviation was found in the 1.59 μm spectra where R1234yf has relatively strong absorption. Further investigation, spectra dependency of refrigerant mixture on molecular interactions and of pure refrigerant on broader range of conditions, including pressure near critical point, are considered to be necessary to improve the estimation model. [ABSTRACT FROM AUTHOR]

The use of heat pumps is increasing worldwide, and knowledge of their properties is becoming more and more important. Although numerous tests regarding heat pumps have been performed, due to the large number of influencing variables, the entire range of input parameters is not covered, and there is no overall picture regarding the range of the coefficient of performance (COP) of heat pumps and their output parameters. This study extends existing research and provides a much more detailed comparison of results for the application of R1234yf and R1234ze(E) refrigerants, including the pressure drop across the evaporator, condenser, and internal heat exchanger (IHX). The appropriate mathematical model for the selected components was defined and verified experimentally. A total of 60 series of measurements were performed at different evaporating and condensing temperatures. The deviation of the numerical simulation results from the experimentally determined results was up to 7.4% for cooling capacity, 8.1% for heating capacity, 7.2% for COP and 6.8% for compressor energy consumption. This study shows that COP increases from 4.77% to 10.73% for R1234ze(E) compared to R1234yf. The use of an IHX in the thermal cycle further increases COP for both refrigerants between 2.61% and 4.99%. [ABSTRACT FROM AUTHOR]

With the growing awareness of dual threats of global warming potential (GWP) and ozone depletion potential (ODP), the theoretical analysis and experimental testing of R1234yf refrigerant as alternative to R134a in a heat pump were analyzed. The results show that when the discharge pressure decreases from 1.6 MPa to 0.9 MPa, the heating COPh of R134a and R1234yf heat pumps decreases by 26.97% and 28.78%, respectively. When the evaporation temperature increases from −10 to 10°C, the heating COPh of R134a and R1234yf heat pumps increases by 12.68% and 20.88%. When the cooling water volume flow increases from 0.14m3/h to 0.35m3/h, the heating COPh of R134a and R1234yf heat pumps increases by 13.07% and 6.56%. When the chilled water volume flow increases from 0.35 to 0.53 m3/h, the heating COPh of R134a and R1234yf heat pumps increases by 30.31% and 29.38%. The error of theoretical calculation and experimental testing is between +10% and −15%. [ABSTRACT FROM AUTHOR]

The Linde-Hampson cycle (LHC) exhibits a promising future as a cooling method to achieve cooling temperatures below −40 °C, and are highly desirable in commercial refrigeration. This paper investigated the refrigerant replacement options of low-GWP blends i.e. R1234yf/R1132a, R1234yf/R170, R1234yf/R41 and R1234yf/R744 in the LHC by using thermodynamic analysis. The compressor temperature, cooling capacity, coefficient of performance (COP) and exergy efficiency were chosen as the objective parameters. The modelling results show that the R1234yf/R41 mixture has larger cooling capacities, while the R1234yf/R1132a mixture has higher energy efficiency. Under a typical operating condition, the R1234yf/R1132a mixture attained a COP of 1.4162 and an exergy efficiency of 28.49%, demonstrating high priority for improving energy and exergy performances. Besides, the system performance will be improved significantly with increasing R1234yf mass fraction, but the cooling temperature will also increase. In addition, the condenser and expansion valve are the two components that deplete exergy the most, which should be the focus for performance improvement. These results have important guiding significance for understanding the effects of different operating conditions on the thermodynamic performance of the LHC, and also expand the selectivity towards the refrigeration system and its working fluids.

In this study, three new mixed refrigerants with low GWP values, R1234yf/R134a, R1234yf/R125, and R1234yf/R13I1, were evaluated as replacements for R134a refrigerant using two vapor compression configurations. The experiment revealed that these mixtures can be used as environmentally friendly alternatives for this configuration. [ABSTRACT FROM AUTHOR]

In this paper, the feasibility of two low global warming potential refrigerants R513A and R1234yf as alternatives to R134a was tested in an automotive air conditioning system in winter. The test results showed that the heating capacities of R513A and R1234yf were 2% and 4% lower than that of R134a, and their COP were 3-9% and 6-19% lower than that of R134a, respectively. It revealed that R513A can be used as a transition product to replace R134a, and R1234yf required further improvements to improve the energy efficiency. [ABSTRACT FROM AUTHOR]

• First reported the VLE data of R1234yf + R32 + R125 ternary mixture. • Provided new VLE data for the R1234yf + R32 + CO 2 ternary mixture. • New ternary mixtures model also well describes VLE properties of the binary mixtures. • The PR + WS + NRTL model shows excellent performance. R1234yf as the environmental friendly refrigerant has a low volumetric refrigeration capacity and light flammability. The refrigerant mixtures are expected to achieve excellent thermophysical performance, safety and environmental performance. The vapor-liquid equilibrium (VLE) is one of the most important properties of the mixtures. In this work, the VLE property of R1234yf + R32 + R125 and R1234yf + R32 + CO 2 ternary mixtures were measured along 5 isotherms from 273.15 K to 313.15 K by a recirculation analytical apparatus. The Peng-Robinson (PR) equation of state combined with the van der Waals (vdW) mixing rule (PR + vdW), as well as the PR equation of state combined with the Wong-Sandler (WS) mixing rule and the non-random two-liquid (NRTL) activity coefficient model (PR + WS + NRTL) were used to correlate the VLE data. The model parameters were temperature-dependent and could describe the VLE properties of the ternary and binary subsystems. The results showed that the PR + WS + NRTL model was better than the PR + vdW model. The average absolute relative deviation of pressure (AARD(p)) and average absolute deviation of compositions (AAD(y)) of the PR + WS + NRTL model were 0.4% and 0.003 for R1234yf + R32 + R125 ternary mixture, and were 0.7% and 0.007 for R1234yf + R32 + CO 2 ternary mixture. Experimental results and model calculations showed that both the ternary mixtures were zeotropic. [ABSTRACT FROM AUTHOR]

In this study, the pressure drop of automotive refrigerant pipes with the refrigerant R1234yf is investigated in detail. For this purpose, 1D and 3D simulations are compared with respect to prediction accuracy using liquid lines from a production car. It is shown that for a combined approach of the methods a very good agreement with the measured values can be obtained, whereas simplified modeling of the line as a straight pipe of equal length significantly underestimates the experimental values. The transition pieces between the pipe and the hose are of particular importance, since they account for up to 85 % of the total pressure drop and therefore result in major errors if neglected. If hoses were eliminated, the lines could be designed smaller, resulting in a charge reduction of up to 56 %. [ABSTRACT FROM AUTHOR]

The present research attempts to comprehensively compare the evaporation characteristics of a novel R290/R13I1 (35/65 % by mass) with R1234yf in an offset-strip fin embedded plate heat exchanger. The impact of various testing phenomena, namely saturation temperature (T s) (278 to 288 K), heat flux (q) (4000 to 10,000 W m−2), entry vapor quality (x i) (0.1 to 0.8), and mass flux (G) (40 to 80 kg m−2 s−1) have been explored. Meanwhile, highly potential machine learning algorithms (MLAs) namely Linear Regression (LR), Multi-Layer Perceptron (MLP), and Extreme Gradient Boost regression (XGB) have been employed to predict the evaporation heat transfer coefficient (EHTC) and evaporation frictional pressure drop (EFPD) of the refrigerants. Findings revealed that the EHTC of R290/R13I1 is significantly lower than that of R1234yf by 7.9–38.8 % in the nucleation boiling or low mean vapor quality (x m) domain, whereas it had superior EHTC by up to 18.2 % in the convective boiling domain (high x m). Interestingly, there was a dry-out incidence at mid-x m ranges (0.35–0.5) for both refrigerants, except for R290/R13I1 at a higher G of 80 kg m−2 s−1. In all cases (except at 10000 W m−2), the EFPD of R290/R13I1 increased by 0.3–11.1 % compared to that of R1234yf. The evaporation thermo-hydraulic performance (ETHP) factor analysis revealed that utilizing R290/R13I1 could perform satisfactorily in the convective boiling domain (x m > 0.5) with an ETHP factor ranging between 0.8 and 1.08, especially at high q, high T s , and low G conditions. New empirical correlations have been developed based on the experimental dataset for the EHTC and EFPD of the considered refrigerants with an mean absolute error (MAE) of up to 14.7 % and 13.4 %, respectively. Among the three MLAs with different enhancement methods, the EHTC and EFPD predictions using MLP, in combination with principal component analysis and hyperparameter tuning, had superior performance, with MAEs of 0.1119 and 0.0581, respectively, for R1234yf, while they were 0.1726 and 0.0482 for R290/R13I1. [ABSTRACT FROM AUTHOR]

• The schematic mechanism for R1234yf combustion were revealed in unimolecular lysis reactions, colliding reactions with oxygen molecules, collision reaction with active radicals (H and OH radicals). • The new chemical reaction equations for the combustion of R1234yf were proposed. • This paper provided an effective method to establish the combustion mechanism of flammable hydrofluoroolefins. To describe the combustion process of hydrofluoroolefins (HFOs) 2,3,3,3-tetrafluroropropene (R1234yf), a kinetics mechanism was developed. On the M06–2X/6–311++ G (d,p) level, dynamic calculations have been performed using the density function theory (DFT) method. Proposed R1234yf kinetic reactions included unimolecular decomposition and intermolecular reactions, such as collisions with O 2 , OH, and H radicals. The results indicated that R1234yf combustion is a step-by-step chain reaction involving chain initiation (unimolecular lysis and collision reaction with oxygen), chain transmission (collision reactions with free radicals), and chain termination. In conjunction with the priority rule of kinetics reactions, a schematic diagram of the primary microscopic combustion pathways for R1234yf was created at 298.15 K and 1 atm. All the simulation results could provide a data basis to establish the kinetic model of hydrofluoroolefin pyrolysis and combustion. In addition, to verify the product direction of the reaction path, experiments were conducted to determine the properties of the R1234yf combustion products. [Display omitted] [ABSTRACT FROM AUTHOR]

• Heat transfer of supercritical R1234yf was experimentally investigated in a horizontal micro-fin tube. • Operating parameter effects on heat transfer were analyzed. • Heat transfer comparisons were conducted between R1234yf and R134a. • Prediction accuracy of existing correlations for R1234yf was analyzed. R1234yf is regarded as an ideal substitute for R134a in supercritical organic Rankine cycles. This study experimentally analyzed the convective heat transfer coefficients of supercritical R1234yf in a micro-fin tube. The experiments show the influence of the system operating parameters including pressure, heat flux and mass flux on the heat transfer. Then, this paper compares the heat transfer rates for R1234yf and R134a at supercritical pressures and the ability of existing correlations to predict the heat transfer coefficients with R1234yf. The results show that as q / G increases, the buoyancy increases Nu bottom , while the variations in Nu top are divided into two regions based on the bulk fluid enthalpy. The influence of pressure on the heat transfer is also related to the bulk fluid enthalpy. When the bulk fluid enthalpy is less than a critical value, Nu bottom and Nu top both increase with decreasing pressure and then decrease above this critical enthalpy. The heat transfer coefficient is no longer enhanced at the top with large buoyancy forces. For low mass fluxes, the heat transfer coefficients of R134a and R1234yf are similar. For high mass fluxes, the heat transfer coefficients of R134a are higher than those of R1234yf. The Wang correlation, that was based on R134a data, more accurately predicts the heat transfer coefficients than other correlations for supercritical R1234yf in the horizontal micro-fin tube. Among all the 4050 experimental points, 90.17% of Nu top and 84.49% of Nu bottom were predicted with errors of less than 30% by the Wang correlation. [ABSTRACT FROM AUTHOR]

The international community limits the usage of higher global warming potential (GWP) refrigerants like R134a in refrigeration and air-conditioning systems. In view of this, the present study focuses on the low-GWP alternatives to R134a during condensation inside a smooth and dimpled tube. The refrigerants considered for this study are propane (R290), 2,3,3,3-tetrafluoropropene (R1234yf), and 1,3,3,3-tetrafluoropropene (R1234ze). The geometric specifications of smooth and dimple tubes are 8.38 mm ID with 1.5 m length. The operating conditions are saturation temperature of 40°C, mass flux ranging between 50 and 200 kg m−2 s−1, and dryness fraction of 0.5 and 0.75. The flow field was assumed to be transient, three-dimensional and turbulent while the VOF model was used to solve the governing equations. The effect of mass flux and dryness fraction was studied with R134a and its alternatives. The simulated void fraction values are compared with experimental values and empirical correlations. In this study, the total pressure drop was reduced by 15 and 20% with smooth tube and 11 and 16.7% with dimpled tube by using R1234yf at the quality of 0.5 and 0.75. However, it was increased with R290 and R1234ze. The power consumption was reduced by using R1234yf as a substitute to R134a and the thermophysical properties are quite similar. [ABSTRACT FROM AUTHOR]

An increase in global warming potential and other environmental concerns are demanding new environmentally friendly refrigerants. For effective performance of refrigeration and air conditioning system condenser design play a vital role. Experiments were conducted to study the condensation of R1234yf refrigerant inside a copper tube of 8.4 mm in diameter and 750 mm in length. The heat transfer coefficients of refrigerant were calculated against mass flux varying from 150–300 kg/m² s, quality of refrigerant 0.3 to 0.8, and saturated temperature 30 and 500 C. The experimental heat transfer coefficients were compared to the heat transfer coefficients by the recent MM Sha correlation. The experimental results are in good agreement with an absolute mean deviation of nearly 20% with the MM Sha heat transfer coefficient. [ABSTRACT FROM AUTHOR]

Flow boiling systems onboard some flight vehicles operate under hypergravity conditions. Many investigations in frictional pressure drop (FPD) of two-phase flow boiling in channels have been conducted extensively under normal gravity (Earth's gravity, 1 g) and microgravity, while few under hypergravity so far. This study presents the experimental investigations into the effects of hypergravity levels on two-phase flow boiling FPD, with refrigerant R1234yf flowing in an electrically heated horizontal mini-tube of 2.01-mm inner diameter. The experimental range of parameters was gravity levels of 1–3.16 g, mass fluxes of 365 and 570 kg/m2 s, saturation pressures of 0.62 and 0.70 MPa, heat fluxes of 47.6 and 97.5 kW/m2, and vapor qualities up to 0.985. The effects of gravity, vapor quality, heat flux, mass flux, and saturation pressure on FPD were analyzed. The results demonstrate that the flow boiling FPD increases with increasing vapor quality x up to around 0.7, and decreases sharply with increasing quality when x > 0.7. The FPD increases significantly with increasing mass flux and negligibly with increasing gravity level, heat flux and saturation pressure. The experimental data were compared with 13 saturated flow boiling FPD correlations for normal gravity, and the Xu and Fang (2012) correlation has the highest prediction accuracy, with the mean absolute deviation (MAD) of 8.0%. [ABSTRACT FROM AUTHOR]

A new fundamental equation of state is presented for 2,3,3,3-tetrafluoroprop-1-ene (R1234yf). The equation is valid from the triple point temperature (121.6 K) to 410 K at pressures up to 100 MPa, where typical expanded uncertainties (k = 2) in calculated properties from the equation are 0.1 % for vapor pressures at temperatures above 270 K and 0.3 % at lower temperatures, 0.1 % for liquid densities at pressures below 40 MPa and 0.25 % at higher pressures, 0.2 % for vapor densities, 0.02 % for vapor phase sound speeds, 0.05 % for liquid phase sound speeds, 1 % for vapor phase isobaric heat capacities, 2 % for liquid phase isobaric heat capacities, and 2 % for liquid phase isochoric heat capacities. At very low temperatures around 200 K, uncertainties for vapor pressures may be larger than 0.5 %. Various plots of constant-property lines demonstrate that not only does the equation exhibit correct behavior over all temperatures and pressures within the range of validity, but also that it shows reasonable extrapolation behavior at extremely low and high temperatures, and at high pressures and densities. The equation of state is the best currently available property representation for R1234yf, and has been adopted as an international standard by the ISO working group, which recently revised ISO/DIS 17584 (Refrigerant properties). [ABSTRACT FROM AUTHOR]

This study compares the performances of two-phase refrigerant cooling (TPRC) using two refrigerants, namely R290 and R1234yf, in battery thermal management systems. A compact and energy-efficient brazed plate heat exchanger with an offset strip fin is employed as a cold-plate evaporator and experiments are conducted to examine its heat-transfer characteristics. Key performance parameters including the heat-transfer coefficient (HTC), pressure drop (PD), and wall temperature (T w) are assessed at discharge rates (C-rates) of 1, 1.25, and 1.5C, saturation temperatures (T sat) of 16 °C and 20 °C, the mass flux of 50 kg/m2s, and inlet vapor-quality values of 0.1–0.8. The results show that R290 offers a higher HTC and lower PD for all C-rates compared with R1234yf for T sat = 16 °C and 20 °C. The HTC increases by 107%–113% for 1.5–1C at T sat = 16 °C, and 84% (1.5 and 1C) and 70% (1.25C) at 20 °C. Similarly, the PD decreases by 6.7%–10.1% for 1–1.5C at T sat = 16 °C and approximately 10% for all C-rates at 20 °C. Compared with R1234yf, R290 maintains a T w that is 1.1 °C and 0.7 °C lower at T sat = 16 °C and 20 °C, respectively. Results of critical heat transfer coefficient (CHTC) analysis confirm that R290 performs better than R1234yf at T sat = 16 °C in terms of HTC increment and T w reduction and that the critical HTC of R290 is higher than that of R1234yf by 80% and 40% for T sat = 16 °C and 20 °C, respectively. Additionally, using R290 instead of R1234yf in the TPRC system yields a higher level of cooling efficiency at vapor-quality values of 0.4–0.5. In addition, an artificial neural network model is used to predict the experimental results, where a root-mean-square error of 2.3%–3.5% is indicated. Using this trained model, the HTC and PD are predicated at intermediate C-rates (1.1–1.4C) and the results are discussed. • R290 outperforms R1234yf in battery cooling, offering higher HTC and lower PD. • HTC increases by 107%–113% for 1.5–1C at 16 °C and 84%–70% at 20 °C. • PD decreases by 6.7%–10.1% for 1–1.5C at 16 °C and by ∼10% at 20 °C. • R290 maintains lower inner wall temperature compared to R1234yf. • ANN model predicts with RMSE of 2–3%, aiding HTC and PD estimation. [ABSTRACT FROM AUTHOR]

• A novel double-stage in series ejector refrigeration system has been investigated. • Comparisons have been made between single-stage and double-stage ERS. • The double-stage in-series ejector enhances the performance up to 160 %. • The performance of R600a and R290 are higher than R134a and R1234yf, respectively. • Double-stage ERS widen the range of condenser and evaporator temperatures. Ejector refrigeration systems (ERS) are promising refrigeration systems that can replace conventional vapor compression systems, because of their ability to operate by thermal energies of low grades and their capability to be integrated with renewable energy sources. However, there are restrictions concerning its low system COP, limited range of operating conditions, and high sensitivity of the performance to the variation of operating conditions. Therefore, this present paper introduces a detailed mathematical model to design and investigate the performance of a novel double-stage in-series ERS, which is believed to overcome the abovementioned restrictions of the single-stage ERS. The present work investigates the critical operating points of the double-stage in-series ERS to reach the maximum COP. Four refrigerants are employed in the analysis, R600a and R134a are compared to each other as they are widely used; additionally, R1234yf and R290 are compared to each other, as they represent the future refrigerants. The comparison shows that double-stage in-series ERS improves the system performance and ability to withstand a high range of operating conditions with low COP variations. Double-stage in-series ERS can result in performance improvements ranging between 3 % to 160 % depending on the refrigerant and its operating condition. Moreover, the usage of double-stage in-series ERS gives the chance to operate at low evaporator temperatures below 0 °C and high condenser temperatures above 50 °C, which is not reachable by single-stage systems. Furthermore, the analysis shows that R600a and R290 have higher performance than R134a and R1234yf, respectively. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) absorption characteristics of heat pump refrigerants, difluoromethane (R32), 2,3,3,3-tetrafluoropropene (R1234yf) and those mixture, R454C, were experimentally measured in liquid phase under various temperature and pressure conditions to obtain fundamental NIR absorption characteristics in a circulating lubricant free cycle. Molar attenuation coefficients at wavelengths of 1.59, 1.64, 1.70 and 1.78 μm were obtained using 1.50 μm wavelength data as a reference spectrum. The evaluated attenuation coefficients showed distinctive difference between each refrigerant. The dependency of the coefficient on pressure was negligibly small, while slight dependence was observed on temperature. In addition, the absorption dependency on the thermal conditions were compared between the flows with and without lubricant oil. The absorption characteristics observed in the lubricant contained flow reported in the previous work were in 99% confidence interval of pure refrigerant and the impact of lubricant were inferred to be negligibly small. Moreover, the coefficients of R454C were correlated with those estimated from each of R32 and R1234yf measurements with a weight average model. Although the estimation from the elementary computation showed qualitative agreement with the experimental data, deviations unique to the energy band of radiation were observed. • Experimental measurement of near-infrared absorption characteristics of R32, R1234yf, and R454C in the liquid phases of a lubricant-free refrigeration cycle. • Attenuation coefficients measured at various wavelengths, revealing insights into pressure and temperature dependencies. • Comparison of absorption data between lubricant-free and lubricant-containing refrigerant flow. • Correlation of absorption characteristics of R454C with pure R32 and R1234yf. [ABSTRACT FROM AUTHOR]

In this work, the mutual diffusivities of difluoromethane (R32) and 2,3,3,3-Tetrafluoropropylene (R1234yf) dissolved in Polyalkylene glycol (PAG) lubricant were studied experimentally based on the principle of dynamic light scattering. The pressure range of mutual diffusivity measurement is from 0.142 MPa to 3.371 MPa, and the temperature range is from 293.15 K to 353.15 K. The experimental data were correlated as the equation of temperature and pressure. The average relative deviation between the experimental data and the model is less than 1.34%. The results show that when the temperature is constant, mutual diffusivities of R32/PAG and R1234yf/PAG mixture decrease with the increasing of the solubility of refrigerants. The mutual diffusivity of R1234yf/PAG is less than that of R32/PAG at the same temperature and solubility. This may be due to the longer length of the R1234yf molecule and greater polarity, which results in the difficult diffusion in the lubricant. The molecular radius (0.164 and 0.299 nm) for the mutual diffusivity of R32 and R1234yf in PAG lubricants were obtained according to the Einstein-Stokes equation. The obtained radius values are within a reasonable order of magnitude compared to literature values. Since the molecular radius of R32 is smaller than that of R1234yf, which is also consistent with the experimental results in this work that the mutual diffusivity of R32 dissolved in PAG is larger than that of R1234yf. [ABSTRACT FROM AUTHOR]