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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.

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]

This study aimed to investigate the effect of changing the indoor unit air flow rate on the performance of an automobile heat pump with a suction line heat exchanger. Using a four-way valve, the automotive heat pump system was developed by reversing the refrigerant direction in the automobile air conditioning system, excluding the compressor. A suction line heat exchanger was added to the test system to enhance heat transfer between the liquid and suction lines of the automotive heat pump system. Performance comparisons were first performed for R134a and R1234yf by disabling the suction line heat exchanger. Then, the suction line heat exchanger was activated for R1234yf, and the tests were repeated. Performance comparisons were made for two different compressor speeds and three different indoor unit airflow speeds. It was found that using the heat exchanger in R1234yf operations improved the heating capacity, compressor discharge temperature and coefficient of performance by approximately 1.8 %, 5.1 % and 5.9 %, respectively. The heating capacity of the heat pump system using R134a, R1234yf, and R1234yf with the suction line heat exchanger was determined to be in the range of 2.46–3.29 kW, 2.35–3.04 kW, and 2.39–3.11 kW, respectively. An increase in the airflow speed of the indoor unit from 1.4 m s−1 to 3.2 m s−1 resulted in an average decrease of approximately 12.3 % in the compressor discharge temperature. In contrast, the heating capacity and coefficient of performance increased by approximately 11.8 % and 14.4 % on average, respectively, for R1234yf operations with the heat exchanger. This study revealed that by optimizing the air flow rate in the R1234yf heat pump system with a suction line heat exchanger, improvements in the heating capacity and coefficient of performance can be achieved, thus providing better thermal comfort in the passenger compartment.

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]

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]

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]

• 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]

• 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]

With the increasing global requirements for environmental protection, refrigerants with ODP of 0 and low GWP are widely concerned and applied. In this paper, the CFD numerical method simulates the R134a centrifugal compressor directly replaced by R1234yf and R1234ze(E). The results show that at the same compressor rotational speed, using R1234yf to replace R134a directly can obtain a higher cooling capacity, but it reduces COP by about 12.5%; using R1234ze(E) to replace R134a directly reduces the cooling capacity under partial working conditions, the COP is reduced by about 7.0%. When the evaporation temperature, condensation temperature, and cooling capacity are the same, compared with the R134a unit, the COP of the R1234ze(E) unit is reduced by about 5.14%, and it is reduced by about 8.93% for the R1234yf unit. For the R134a centrifugal chiller, the drop-in replacement of R134a with R1234ze(E) can obtain better system performance compared with R1234yf. [ABSTRACT FROM AUTHOR]

• The gaseous pvTx properties of R134a/R1234yf binary mixtures were studied. • Measurements cover temperatures from (308 to 388) K and pressures up to 5.0 MPa. • A truncated virial EOS for R134a/R1234yf binary mixtures was developed. In the present study, the accurate determination of the vapor phase pvTx behavior of binary mixtures of 1,1,1,2-Tetrafluoroethane (R134a) + 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) by using a Burnett apparatus was demonstrated. Measurements have been performed over the temperature range from (303 to 388) K and at pressures up to 5023 kPa covering the mole fractions of x R134a = (0.000, 0.099, 0.328, 0.523, 0.726, 0.919, 1.000). The combined expanded uncertainties of temperature, pressure, mole fraction and vapor density with a level of confidence of 0.95 (k = 2) were estimated to be 24 mK, 1.6 kPa, 0.01 and within 0.2% over the entire temperature, pressure and mole fraction ranges, respectively. In order to facilitate practical industrial applications and explore the thermophysical behavior of the second and third virial coefficients, the experimental vapor density data of this work were used to develop the virial equation of state with the average absolute deviation of compressibility factor lower than 0.52% for each composition. Furthermore, the obtained gaseous pvTx properties of R134a/R1234yf mixtures were compared with the multi-parameter equation of state of REFPROP 10.0 (Lemmon et al., 2018) and the relative deviations were less than 1.2%. [ABSTRACT FROM AUTHOR]

In this study, in a Vapor Compression Refrigeration System (VCRS) using R134a as refrigerant, R1234yf refrigerant considered as an alternative to R134a has been used as working fluid with the addition of aluminumdioxide (Al2O3) and Carbon NanoTubes (CNTs) nanoparticles. This system has been theoretically investigated in terms of thermodynamics under the same conditions, only by changing the working fluid. Investigations have been performed over a wide range for varying evaporation and condensation temperatures. The system using R134a and R1234yf as the working fluid have been analysed at the same conditions. As a result of the analyses at -7 °C evaporation and 45 °C condensation temperature, the Coefficient of Performance (COP) of the system has been calculated as 1.950 and 1.824 for pure R134a and R1234yf, respectively. There is a difference of 6.46% between COP values. Similarly, a difference of 6.44% between the second law efficiencies (exergy efficiencies) have been found as well. Thus, R1234yf refrigerant with the addition of Al2O3 and CNTs nanoparticles has been used as the nanorefrigerant instead of R134a refrigerant at the same conditions in analyses. As a result of the analyses, it has been observed that the COP and exergy efficiency increase with the nanoparticle volumetric concentration. Results have revealed that COP and exergy efficiency have increased up to values of 18.46% and 18.43% compared to usage of pure R134a refrigerant at -7 °C evaporation and 45 °C condensation temperatures for the R1234yf/Al2O3 nanorefrigerant, respectively. Similarly, these increases have reached up to values 6.92% and 6.89% for R1234yf/CNTs nanorefrigerant as well. [ABSTRACT FROM AUTHOR]

Various energy and exergy performance parameters of an automotive heat pump (AHP) with R1234yf have been investigated and compared with those of the baseline system with R134a. For this aim, an AHP system was set up from the components of an air-conditioning system employed in a compact car and equipped with instruments for mechanical measurements. It was tested with R1234yf and R134a by changing the compressor speed and air stream temperatures incoming the outdoor and indoor units. Using test data, energy and exergy analyses of the AHP were performed, and its performance parameters were evaluated. The R1234yf system provided conditioned air temperatures in the range of 29.9–59.3 °C, heating capacities in the range of 1.96–3.14 kW and coefficient of performance (COP) values in the range of 2.44–4.56. It yielded 3.3–10.8 °C lower conditioned air temperature, 9.2–15.4% lower heating capacity, 1.6–7.1% lower COP, 13.8–21.6 °C lower compressor discharge temperature, 3.1–19.2% higher total exergy destruction rate per unit heating capacity but significantly less TEWI in comparison with the system with R134a. Moreover, the R1234yf system yielded larger exergy destructions in the outdoor unit, compressor and expansion device but lower exergy destruction in the indoor unit. These findings reveal that R1234yf can be used in AHP systems in expense of less heating capacity, lower COP and higher exergy destruction rate per unit heating capacity in comparison with R134a. [ABSTRACT FROM AUTHOR]

This research presents an energy performance analysis of the heat pump system with internal heat exchanger (IHX). The mathematical model of the heat pump outlined in this paper has been created by the author, it is steady-state with lumped parameters. The experimental validation of the model has been carried out using R1234yf and R134a as refrigerant. The aim of this work is to compare the energy performance in a wide range of operating conditions of a monitored heat pump system using both refrigerants. Finally, the heating capacity for R1234yf was lower from 0.63 % to 7.54 % compared with R134a, while the compressor power was similar from 0.12 % to 3.51 %. The COP values of R1234yf were lower than those obtained of R134a, ranging from 1.39 % to 4.22 %. [ABSTRACT FROM AUTHOR]

In this study, the energetic and exergetic performance merits of an automotive air conditioning (AAC) system using R134a and R1234yf have been investigated. For this aim, a laboratory AAC system was developed and equipped with devices for mechanical measurements. The refrigeration circuit of the system mainly had an evaporator, condenser, liquid receiver, fixed capacity compressor, and thermostatic expansion valve. The tests were performed by changing the compressor speed and air stream temperatures incoming the condenser and evaporator. Based on energy and exergy analysis, various performance parameters of the AAC system for both refrigerants were determined and presented in comparative graphics. It was found that R1234yf resulted in 0.4-10.9% lower refrigeration capacity, 5.5-11.6% lower COP, and 4.7-16.1°C lower compressor discharge temperature, while yielding 9.3-22.3% higher refrigerant mass flow rate and 1.1-3.5°C higher conditioned airstream temperature in comparison to R134a. Moreover, the components of the R1234yf system usually destructed more exergy, and the total exergy destruction rate per unit refrigeration capacity of the R1234yf system was 4.1-15.3% greater than that of the R134a one. [ABSTRACT FROM AUTHOR]

The aim of present work is the evaluation of mechanically subcooled simple vapour compression refrigeration system on the basis of energy and exergy analysis, and compatibility of alternative low GWP and zero ODP HFOs R1234yf and R1234ze to replace HFC 134a. A computer program has been developed in Engineering Equation solver software to compute the system performance parameters such as COP, exergetic efficiency, total exergy destruction and exergy destruction ratio. The effect of degree of subcooling (5 to 30°C), evaporator temperature (-30°C to 15°C), effectiveness of liquid vapour heat exchanger (0.2 to 1.0) and compressor efficiency (0.4 to 1.0) has been investigted on the performance parameters viz. exergy desturction, exergy destruction ratio (EDR) and exergetic efficiency of the system components. The results of current analysis highlight that the R1234ze is the best alternate refrigerant considered in the analysis and can replace R134a as the COP and exergetic efficiency of R1234ze are 1.87% and 1.88% more than that of R134a for 30°C of subcoooling. However, R1234yf offers lower performance than R134a. The components condenser and evaporator are the sites of highest and lowest exergy destruction respectively for the refrigerants considered. [ABSTRACT FROM AUTHOR]

R134a, one of the most commonly used refrigerants especially for air conditioning (AC) systems, will be banned in automotive air conditioners after 2022 due to a high global warming potential (GWP). R152a and R1234yf are considered as two potential low GWP drop-in alternatives to R134a due to similar thermodynamic properties. In this paper, the performance of R152a, R1234yf, and R134a in an oil-free vapour compression refrigeration (VCR) system is investigated. The absence of oil lubricant enables a wide range of refrigerant selection and highly efficient refrigeration cycle. Experiments for R152a, R1234yf, and R134a were conducted over wide range of operating conditions. The results show that R1234yf is similar to R134a in terms of operating pressure and temperature, but R1234yf has an 11% and 16% deterioration in cooling capacity and coefficient of performance (COP) respectively. The higher volumetric efficiency, adiabatic efficiency and cooling capacity of R152a contributes to a 13% and a 6% higher cooling capacity and COP respectively than that of R134a. At an evaporator temperature of 0 °C, the COP of R152a, R1234yf, and R134a are 2.8, 1.8, and 2.3, respectively. Though flammability restricts the use of R152a in conventional automotive air conditioners, R152a can be considered as a more promising alternative to R134a for oil-free automotive air conditioning than R1234yf due to its high efficiency, low cost, and reasonable safety level benefiting from the absence of oil lubricants.

With the increasing global requirements for environmental protection, refrigerants with ODP of 0 and low GWP are widely concerned and applied. In this paper, the CFD numerical method simulates the R134a centrifugal compressor directly replaced by R1234yf and R1234ze(E). The results show that at the same compressor rotational speed, using R1234yf to replace R134a directly can obtain a higher cooling capacity, but it reduces COP by about 12.5%; using R1234ze(E) to replace R134a directly reduces the cooling capacity under partial working conditions, the COP is reduced by about 7.0%. When the evaporation temperature, condensation temperature, and cooling capacity are the same, compared with the R134a unit, the COP of the R1234ze(E) unit is reduced by about 5.14%, and it is reduced by about 8.93% for the R1234yf unit. For the R134a centrifugal chiller, the drop-in replacement of R134a with R1234ze(E) can obtain better system performance compared with R1234yf.

Now a days Fridges and Air-conditioners are mostly used in domestic environment. The CFCs have been almost ruled out since 1995 due to their huge impact on the ozone layer, due to the above problem HFC refrigerants are introduced but these are having a high GWP value, which causes environmental pollution. But later Kyoto protocol came into existence which stated the need to replace HFC’S due to their high GWP values. Along with the prevention of environmental pollution, performance improvement also very important. Performance of a conventional refrigeration system can be improved with the help of liquid-suction heat exchanger. So in this paper, Thermodynamic analysis of domestic refrigerator with liquid suction heat exchanger using R134a as a refrigerant was done and the results are compared with various low gwp refrigerants like, HFC152a, HC290, HC600a, HFO1234yf and HFO1234ze(E) as a possible alternative to 134a without any modification to the system. Performance parameters like COP, Refrigeration Effect, Compressor Work and Pressure ratio have been reported at various operating parameters like evaporator temperature, condenser temperature. Theoretical results revealed that all the low GWP refrigerants used in the analysis have a slightly lower performance the R134a at various condenser and evaporator temperatures

In the present paper, the experimental results of the use of R1234yf and R1234ze(E) as drop-in alternatives of R134a in a water-to-water heat pump are discussed. The heat pump is firstly tested with R134a, to establish the baseline performance, and, then, is tested with the two above-mentioned refrigerants considering the same compressor shaft rotational frequency and the same outlet temperatures of the secondary fluids from the evaporator and the condenser. The obtained results show that, compared to the R134a, the use of R1234yf leads to a reduction of the heating capacity and of the COP up to 9.80% and 7.39% respectively, whereas with the use of R1234ze(E) the capacity reduction achieves a maximum of 33.82% while a COP variation in the range −12.27% to +4.32% is found. A second group of tests is carried out varying the rotational frequency of the compressor shaft with the aim of matching the baseline R134a heating capacity. The results indicate an increase in the shaft rotational frequency up to 16% with R1234yf and up to 50% with R1234ze(E) which, however, leads to a maximum reduction of the heat pump COP respectively equal to 7.38% and to 18.11%. [ABSTRACT FROM AUTHOR]

To improve the efficiency of mobile air conditioning and to meet the need of protecting the environment, performance characteristics of the R1234yf heat pump were tested under various conditions in a cold climate. R1234yf is considered a promising replacement for R134a because of its low global warming potential (GWP). Many studies have examined the cooling performance of R1234yf, but little attention has been focused on its heating performance in cold climate. In this work, the system performance of R1234yf heat pump was analyzed and compared with that of R134a under different influencing factors such as charge, outdoor temperature, indoor temperature, outdoor wind speed, indoor air mass flow rate, compressor speed, inner condenser width, and economized vapor injection (EVI). The results obtained are presented in detail from the view of experimental analysis and comparison. [ABSTRACT FROM AUTHOR]

The Montreal Protocol on ozone-depleting substances and the Kyoto Protocol to the United Nations Framework Convention on Climate Change are affecting the refrigeration industry. Both documents have banned the use of substances responsible for ozone depletion and global warming. The automotive indus- try must keep up with these changes. The design of cooling systems in cars must meet the requirements of new refrigerants. In addition, changing the production profile of large car compa- nies towards electric and hybrid cars increases this need. This development has a significant impact on the solutions installed in passenger vehicles. The paper presents a critical assessment of R134a, R1234yf, and R744 in passenger car heat pump sys- tems. The possibility of their use in common air conditioning systems with motor drive and in the heat pump of an electric vehicle was presented. The calculation algorithm of the heat pump system has been developed, showing the in fluence of the physical properties of refrigerants on efficiency during the pro- cess of the designed heat pump system. The impact of using new refrigerants in the car production process has been ana- lyzed and commented on. The in fluence of thermodynamic and ecological properties of refrigerants on the process of designing a heat pump system using a calculation model was described. Types of heat pump in electric cars and a calculation model were presented. [ABSTRACT FROM AUTHOR]

In this 21st century, scientific enterprise has a driving force known as safety value and care value for environment; researchers are striving to fulfill these values. Policies like the Montreal Protocol and the EU Directives incentivize this research. The feasibility of R1234yf is introduced in car air conditioner application. This is an experimental study on car air conditioning system with drop in substitute R1234yf for R134a. For the experimental study, a test rig was developed, in which actual car conditions were simulated. Performance parameters like work input to the compressor, coefficient of performance, refrigerating capacity and overall heat transfer coefficient were taken into consideration. [ABSTRACT FROM AUTHOR]

In this study, performance characteristics of an automotive heat pump (AHP) system using R1234yf and R134a were investigated. Compressor speeds, air temperature and air flow velocity significantly influence the system performance parameters. Therefore, the effect of compressor speeds, air flow velocities and temperatures on the system performance characteristics were evaluated under various test conditions. Optimum experimental conditions were arranged to determine the performances of the AHP system. As a result, the heating performance of R1234yf is lower than R134a. The heating performance of AHP systems gets higher as air flow velocities drop. While the air flow velocities raised up from 1.2 to 4.5 m s−1, the heat capacity was decreased by 15%. Change in air velocities plays more role on the performance characteristics than the change in ambient temperature at low air flow velocities. Comparing the suction and discharge pressures of both the R134a and R1234yf, R1234yf is higher because of its vapour densities. Finally, R1234yf can be used in AHP systems for both cooling and heating applications. [ABSTRACT FROM AUTHOR]

• R1234yf and R1234ze(E) are gaged as R134a low GWP alternatives. • New R1234yf experimental data are presented. • R1234yf, R1234ze(E) and R134a performance is compared. • Several literature correlations are assessed. R134a is ongoing a phase-down process in several countries and R1234yf can be a viable low GWP alternative together with R1234ze(E). Since new experimental data are always requested by researchers and industry to increase the global database, to assess the existing correlations, and to expand the knowledge about the refrigerant applications, in this paper more than 100 new heat transfer coefficient and frictional pressure drop data are presented during R1234yf flow boiling inside a 4 mm inner diameter smooth copper tube. Three saturation temperatures 10°C, 15°C and 20°C were investigated and critically discussed, for each temperature the heat flux ranged from 15 to 30 kW m−2 and the mass velocity from 300 to 600 kg m−2 s−1. Furthermore, some literature correlations were implemented and carefully examined and their deviations are reported. Finally, the R1234yf heat transfer performance is compared against R1234ze(E) and R134a, highlighting the peculiarities of each alternative molecule. R1234ze(E) outperforms the other refrigerants at high vapor qualities but both R1234yf and R1234ze(E) can be viable low GWP substitutes to R134a, if the new design is able to take advantage of the qualities of each refrigerant. [ABSTRACT FROM AUTHOR]

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In this study, the two-phase pressure drop of R1234yf refrigerant (as an alternative to R134a) in a smooth horizontal tube is investigated. Tests are carried out and under several conditions of vapor quality (0% to 100%), mass velocity (200, 300 and 400 kg/m²s), heat flux (0, 7 and 14 kW/m²) and evaporation temperatures (20 °C and 30 °C). The internal diameters tested are 3.2 mm, 4.8 mm, 6.4 mm and 8.0 mm. A comparison of pressure drop between R1234yf and R134a is also carried out. The results demonstrate that the two-phase pressure gradient of R1234yf is approximately 20% lower than that of R134a. The experimental data is compared with 19 correlations from the literature. From this comparison, it is concluded that the experimental data are in accordance with the correlation proposed by Xu and Fang with a mean absolute error of 20% and with approximately 65% of the data predicted within a ±30% error band. [ABSTRACT FROM AUTHOR]

• Experiments on void fraction of R1234yf in a horizontal smooth tube. • Effects of experimental conditions on void fraction of R1234yf is analyzed. • Experimental data of void fraction of R1234yf are compared with correlations. • The quick close valve method was used to measure the local void fraction. Void fraction is an important parameter to design and simulate thermal systems involving two-phase flows. In this research, an experimental investigation of the void fraction in adiabatic two-phase flow of R1234yf in horizontal and smooth tubes with an internal diameter of 4.8 mm was carried out. For the experimental tests, the vapor quality ranges from 0.1 to 1 while two saturation temperatures (15 and 25°C) and two mass flow rates (180 and 280 kg. m −2s−1) are investigated. The quick-closing valve(s) method is used to measure the volumetric void fraction. Tests are also undertaken with R134a used as a reference in this study. The results highlight that the void fraction of R1234yf is 5% lower than that for R134a. In addition, the experimental data of R1234yf were compared against seven correlations from the literature: the Baroczy and the Hughmark correlations were shown to provide the best prediction, with a mean absolute error of 2% and 3.2%, respectively. [ABSTRACT FROM AUTHOR]

In this work, the thermodynamic analysis of dedicated mechanically subcooled vapour compression refrigeration system is presented. A software based computer program in EES has been formulated for computation of the performance results. The effect of varation of degree of subcooling (5-30°C), evaporator temperature (-20 to 10°C) and condenser temperature (30-50°C) has been investigated for energetic and exergetic performance of the system. The analysis of the system has been carried out using zero ODP and very low GWP (1 to 4) refrigerants viz.HFO-R1234ze and R1234yf to compare the performance of HFC-R134a. The results depicts that the COP and exergetic efficiency of dedicated subcooled VCR cycle are better than that of simple VCR cycle. Refrigerant R1234ze performs better than R1234yf and comparable to R134a. [ABSTRACT FROM AUTHOR]

Highlights • This paper investigates R134a, R152a, R1234yf, and R1234ze(E) condensation inside a smooth tube. • The transition between gravity-controlled and forced convection condensation occurs in the range of Re eq 10,000–20,000. • R152a, R1234yf and R1234ze(E) exhibit heat transfer and hydraulic performances very similar to those of R134a. • R152a, R1234yf and R1234ze(E) are very promising as long-term low GWP substitutes for HFC134a. Abstract This study performs the comparative analysis of R134a, R152a, R1234yf and R1234ze(E) condensation inside a 4 mm ID smooth tube. The experimental tests were carried out at three different saturation temperatures, 30, 35, and 40 °C, at different vapour qualities and mass velocities to evaluate the specific contribution of refrigerant mass flux, mean vapour quality, and condensation temperature (pressure). The frictional pressure drops exhibit great sensitivity to all the operating variables considered, while the condensation heat transfer coefficients show great sensitivity only to refrigerant mass flux and mean vapour quality. The transition between gravity dominated and forced convection condensation occurred in the range of the equivalent Reynolds number 10,000–20,000. The Friedel (1979) correlation was able to predict properly the whole set of frictional pressure drops data, while the Akers et al. (1959) model gave a very good estimation of the forced convection condensation heat transfer coefficients. R152a, R1234yf and R1234ze(E) show condensation heat transfer and pressure drop performances similar to those of R134a, therefore they seem valuable long-term low GWP substitutes for R134a. [ABSTRACT FROM AUTHOR]

In this study, the energy parameters (i.e., cooling capacity and COP) were theoretically investigated for three different vapour compression refrigeration system (basic cycle, basic cycle with liquid-to-suction heat exchanger and two-stage cascade cycle) for which R1234yf, R1234ze(E), R513A, R445A and R450A alternative refrigerants with low GWP value were used instead of R134a. The studied refrigerants demonstrated similar thermodynamic behaviour. The exergetic efficiency of the systems was also compared. The comparison of the energy parameters was carried out for two different evaporation temperatures (-30 and 0°C) and two condensing temperatures (40 and 55°C). According to the calculation results, R450A which almost has the same COP values as R134a comes into prominence with 58% lower GWP value compared to R134a. Among the studied refrigeration cycles, system with LSHEX can be suggested for providing a better effect in terms of COP for the considered refrigerants and temperature cases as well as assumed system parameters. It was seen for the investigated cycles that the highest exergetic efficiency could be obtained in the case of R445A. [ABSTRACT FROM AUTHOR]

This study is directed to propose a method for enhancing the energy parameters of the refrigeration systems operating with R134a which generally presents low performance of the units. Hence, R134a was experimentally compared with HFO-based refrigerants of R1234yf and R1234ze(E) having low-GWP. Additionally, plate-type liquid to suction heat exchanger (LSHX) was utilized in order to determine its effect on the system's energy performances. The evaporation temperatures were −9, −4.5 and 0 °C while the condenser temperatures were 40, 45, and 50 °C in the experimental work. The cooling capacity and power consumption of R1234ze(E) were noticed lower, however its COP was higher compared to R1234yf. It was also figured out that COP of the system with LSHX using R1234ze(E) was better about by 3% than that without LSHX which operated with R134a. The results of the present study indicated that the presence of LSHX caused improved COP and lower power consumption of the refrigeration system. [ABSTRACT FROM AUTHOR]

This study is developed to evaluate the possibility of R1234yf to be a drop-in replacement for a pre-designed system with R134a, including the characterization of control system in a vapor compression system. The control algorithms are required for regulating the refrigerant flow rate into the evaporator and their control parameters depend intrinsically on refrigerant fluid. This paper presents a comparison of the effects of R134a and R1234yf refrigerants on the transient response of an evaporator operating with water as secondary fluid (counter-flow). The dynamic heat exchanger distributed model combines principles of thermodynamics, heat and mass transfer with empirical correlations, which are proposed in the literature, in order to compute the void fraction, pressure drop and heat transfer in two-phase flow. Experimental tests are carried out on a fixed refrigeration system for cooling capacity less than 3 kW, with constant condensation conditions, variable evaporating temperature and compressor speed to validate the model. The results demonstrated that a good agreement between simulation results and experimental data was achieved. The evaporation temperature data were within ± 1   °C error band. Furthermore, comparative simulations between the refrigerants R-134a and R-1234yf exhibited a similar dynamic behavior during a step at the inlet mass flow rate, and the gain and time constant for superheat control were not considerably modified. Therefore, the refrigerant changing does not demand many changes in the expansion device control strategy. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the R1234yf drop-in performance in an R134a small power vapor-compression refrigeration system. Experiments were performed for two compressor supply frequency values of 40 and 60 Hz, evaporation temperatures from −5 to +5 °C and condensation temperatures of 45, 50 and 55 °C. From the experimental measurements, parameters such as the cooling power, compressor electric power or the energy efficiency ratio (EER) of the system are obtained and compared between the two refrigerants. Results show that R1234yf may be an adequate drop-in refrigerant for R134a as it closely matches its cooling capacity at the expense of lower EER values. [ABSTRACT FROM AUTHOR]

This paper explores the possible use of R1234yf and R1234ze(E) during condensation inside a microfin tube with an inner diameter at the fin tip of 2.4 mm as replacement of R134a. Having thermodynamic properties close to those of R134a, R1234yf and R1234ze(E) are some of its possible replacements for air conditioning and refrigeration systems. Experimental tests were carried out for mass velocities from 300 to 1000 kg m −2 s −1 , vapor qualities from 0.95 to 0.2, at saturation temperatures of 30 °C and 40 °C. From the experimental measurements, it has been possible to calculate the heat transfer coefficient and to measure the frictional pressure drop. Globally speaking, R1234ze(E) shows heat transfer coefficients similar to those of R134a, whereas R1234yf shows slightly lower values. R1234ze(E) frictional pressure drops are some 30% higher than those of R134a, whereas R1234yf shows values similar to R134a. The experimental results of heat transfer coefficient and frictional pressure drop were also compared against values predicted by empirical correlations. [ABSTRACT FROM AUTHOR]

In this study, the performance of a new refrigerant, R1234yf/R134a (with a ratio of 89:11, by mass), was measured as alternative to R134a in automotive air conditioning systems using micro-channel heat exchangers in cooling and heating modes. Test results show that the capacities of R1234yf/R134a and R134a are similar in cooling and heating modes. The COP of R1234yf/R134a was lower than that of R134a by 4–9% in cooling mode, while it was lower by 4–16% in heating mode. The average compressor discharge temperature of R1234yf/R134a was up to 10 °C lower than that of R134a in cooling and heating modes. By adding 11% R134a, R1234yf/R134a can be made virtually non-flammable. In addition, R1234yf/R134a has no ozone depletion potential, with a global warming potential of less than 150, thus meeting the requirement of European mobile air-conditioner directives. R1234yf/R134a can be used as an environment-friendly replacement for R134a in automotive air conditioning systems, with minor modifications. [ABSTRACT FROM AUTHOR]

A laboratory automotive air conditioning (AAC) system was set up and tested for the cases of employing refrigerants R134a and R1234yf. Two different empirical correlations were developed to predict the steady state performance parameters of the AAC system based on some experimental data. The air stream temperatures entering the evaporator and condenser and the relative humidity of the air stream at the evaporator inlet were selected as the input parameters of the proposed correlations, while the output parameters were the cooling capacity, power absorbed by the refrigerant in the compressor, condenser heat rejection rate, coefficient of performance, conditioned air temperature, compressor discharge temperature and the rate of total exergy destruction in the AAC system. Then, the predictions of these correlations were compared with the experimental results which were not used in developing the correlations. The findings suggest that both correlations can be used for accurately predicting the performance parameters of the AAC systems. [ABSTRACT FROM AUTHOR]

This paper presents the experimental comparative performance analysis of an automotive air conditioning (AAC) system using R1234yf and R134a. For this purpose, an AAC experiment setup used for R134a was built to obtain the drop-in performance of a new refrigerant R1234yf. Among the low global warming potential (GWP) refrigerants, R1234yf was particularly chosen due to its similar thermo-physical properties with R134a. However, the system with R1234yf could not perform as efficiently as R134a can. Therefore, an internal heat exchanger (IHX) was employed to enhance the performance of the R1234yf system. After that, the performances of R1234yf and R134a were compared under various compressor speeds and air stream temperatures. The results showed that the cooling capacity and COP of the system with R1234yf were 17.1% and 12.4%, respectively, lower compared to the one with R134a. However, when the IHX was introduced into the system with R1234yf, the cooling capacity and COP values were significantly enhanced by 7.9% and 4.1%, respectively. [ABSTRACT FROM AUTHOR]

This research involves the theoretical aspects of R134a automobile air conditioning system. The main aim of the research is to evaluate the different alternative refrigerants as a drop in substitute of R134a theoretically. For this purpose, thermodynamic properties of different alternative refrigerants i.e. R290, R600a, R407C, R410A, R404A, R152a and R1234yf are compared to R134a. Thermodynamic evaluation of standard rating cycle of vapour compression refrigeration system is carried out. Engineering equation solver and refprop soft wares have been used for the thermodynamic analysis purpose. From thermodynamic analysis, it is derived that R1234yf is best suitable alternative refrigerants as a drop in substitute of R134a . R1234yf has lower coefficient of performance as compared to R134a; however it is best suitable alternative refrigerants as a drop in substitute because it has very low global warming potential and can be substituted in the existing automobile air conditioning system with minimum modification. [ABSTRACT FROM AUTHOR]

In 2014, the Directive 517/2014 was introduced by European Parliament to reduce the use of high-GWP greenhouse gases in the European area in order to limit global climate change in accordance with the objectives marked by the EU Research and Innovation programme Horizon 2020. These restrictions affect the large majority of artificial refrigerants among which R134a is included due to its relatively high GWP 100 (1301). The widely used of R134a in the refrigeration and air conditioning fields reveals the need to identify new low-GWP alternatives. Accordingly, in this work five low-GWP R134a possible choices have been tested and compared in an identical refrigerating facility equipped with a hermetic compressor, under the same operating conditions. The refrigerants used in this analysis are: R290 and R600a (HCs); R134a and R152a (HFCs), and finally, R1234yf and R1234ze(E) (HFOs). All of them have been assayed without changes in the facility, that is, as direct drop-ins . The results obtained from the experimental tests are presented and commented in this work from the energetic point of view. [ABSTRACT FROM AUTHOR]