Refrigerants R1234yf Research Articles

Experimental investigation of the void fractions of refrigerants R32 and R1234yf in a 1 mm diameter horizontal channel using a capacitance-based method

The void fraction of two-phase flow in the 1 mm of channel is investigated in this study. The small channels, including micro to mini-channel, are widely used for developing miniaturized air conditioning systems. In terms of carbon emission reduction, optimizing the refrigerant charging amount based on sufficient information and understanding of the characteristics of the two-phase flow is a noteworthy challenge. The void fraction is a parameter of the two-phase flow that is essential for determining the heat transfer coefficient, modeling the pressure drop, and predicting the refrigerant charging amount. Therefore, the precise measurement and prediction of void fraction in small channels for various refrigerants are required. However, thus far, the void fraction characteristics of small channels have not been actively investigated because of the limited volume inside a single small channel and the relatively high error of the quick-closing valve (QCV) method for small channels. This study proposes a capacitance-based sensor as an alternative method for void fraction measurement of small channels. The newly designed void fraction sensor was fabricated with 7.8 % uncertainty under compensation for manufacturing limitations. The void fractions of refrigerants R32 and R1234yf flowing through smooth small horizontal channels under adiabatic conditions (inner diameter: 1 mm, mass flux: 300–600 kg m−2s−1, saturation temperature: 20–30 °C, vapor quality: 0.025–0.900) were measured. The measurement results were compared with ten existing prediction correlations of five classifications, and the correlations that optimally predicted the void fractions of R32 and R1234yf in the small horizontal channel were presented.

Experimental investigation on condensation heat transfer coefficient and frictional pressure drop of low GWP refrigerant R1234yf on a wavy fin surface

Refrigerant R1234yf is an ideal substitute to replace R134a due to its lower value of global warming potential (GWP). The thermophysical properties of R1234yf are similar with R134a and thus it is considered as a potential replacement for R134a in thermal fluid systems. Further, it was noticed that there is a lack of analysis on the condensation of R1234yf in a brazed plate fin compact heat exchanger (CHE) employing wavy fins. In the present work, condensation heat transfer coefficient and frictional pressure drop of refrigerant R1234yf are investigated in a brazed plate fin compact heat exchanger with wavy fin surfaces. The test condenser with wavy fin surface was selected to examine the condensation heat transfer coefficient and frictional pressure drop using refrigerants R134a and R1234yf for varying mass flux and saturation temperatures. The present study also discusses the dependency of specific kinetic energy of refrigerant on frictional pressure drop. Further, using the experimental data of wavy fin surfaces, suitable correlations for the condensation heat transfer coefficient and frictional pressure drop of R1234yf were proposed. The present paper also reports the comparison made between refrigerants R134a and R1234yf. Comparison between R1234yf and R134a shows that condensation heat transfer coefficient and frictional pressure drop of R1234yf is 9–16 % and 10–17 %, respectively, lower than of R134a in the mass flux range 15–44 kg/m2s.

Experimental study and general correlation for condensation heat transfer coefficient inside microfin tubes

This study investigated the condensation heat transfer characteristics of the pure refrigerants R1234yf and R32 in a microfin tube with a small diameter of 3.5 mm outside diameter and 3.18 mm inner mean diameter. Experiments were carried out at mass velocities between 50 and 200 kg m-2 s-1, saturation temperatures of 20 and 30 °C, and vapor quality between 0 and 1. The effects of vapor quality, mass velocity, saturation temperature, and refrigerant properties on condensation heat transfer characteristics were investigated. A new correlation is also developed to predict condensation heat transfer coefficients that can be applied to horizontal microfin tubes with inner diameters between 2.5 and 8.9 mm. The new correlation is validated with the database containing 1240 experimental data points from 10 independent research groups. The comparison results show that the three existing correlations overestimate the heat transfer coefficient data with mean deviation greater than 30.0 %. Meanwhile, the new correlation predicted the present experimental data and other researchers' data with mean deviation of 19.8 %.

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

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

Experimental study of the heat transfer coefficient during condensation of refrigerant R1234yf in a 4.8-mm internal diameter smooth horizontal tube

Experimental study of the heat transfer coefficient during condensation of refrigerant R1234yf in a 4.8-mm internal diameter smooth horizontal tube

Pressure Drop and Heat Transfer Characteristics of TiO2/R1234yf Nanorefrigerant: A Numerical Approach

Global warming is one of the most dangerous ecological issues facing the globe. Refrigerants are a major contributor to global warming. This investigation mainly focuses on the analysis of a greener nanorefrigerant. Nanorefrigerant can improve the efficiency of refrigeration and air conditioning systems that use vapor compression. In the present investigation, mathematical and computational methods are used to assess the heat transfer and pressure drop properties of TiO2/R1234yf. In order to analyze the heat transfer characteristics and the transport features of the innovative nanorefrigerant, appropriate mathematical predictive models were adapted from earlier investigations. The models are validated by the experiments using TiO2/POE nanolubricant as a test fluid. The investigation was conducted with a temperature range of 10 °C to 40 °C and a volume percentage of nano-sized TiO2 particles in R1234yf refrigerant ranging from 0.2 to 1%. According to the research, the introduction of nanoparticles increases viscosity, thermal conductivity, and density. However, as the amount of nanoparticles rises, the specific heat capacity of the nano-enhanced refrigerant decreases. The nanorefrigerant’s heat transfer coefficient and pressure drop are improved by 134.03% and 80.77%, respectively. The outcomes observed from the predictive technique and the simulation approach had an average absolute variation of 9.91%.

Comparative performance investigation of a dual evaporator cycle using an ejector with the conventional cycle using a pressure reducing valve

The performance of a dual evaporator cycle using ejector is compared with a conventional cycle employing pressure reducing valve. In both the systems, high temperature evaporator is considered as a flooded evaporator, thus a separator is employed after the high temperature evaporator. However, low temperature evaporator is a kind of conventional dry evaporator. The comparison of both systems, i.e., conventional and ejector assisted, is done for the same cooling capacities and same dryness fraction at the exit of high temperature evaporator with R134a, R152a, and R1234yf refrigerants. The effects of varying the states of refrigerant at the exit of flooded evaporator, and temperatures of both the evaporators and the condenser are analyzed using Engineering Equation Solver. It is found that the compressor work is reduced in both the cycles with the rise in low temperature evaporator temperature; however, a little variation is observed in the total cooling effect. The cooling effect in high temperature evaporator is increased with the increase in dryness fraction at the exit of the high temperature flooded evaporator, but it is decreased in low temperature evaporator.

Investigation on transport properties, heat transfer characteristics and pressure drop of CuO enhanced R1234yf based refrigerant

In refrigeration systems, one of the potential heat transfer fluids is nano-refrigerant. It can boost the performance of air conditioning and vapour compression refrigeration systems. In this investigation, the heat transfer characteristics and pressure drop of CuO/R1234yf are analysed by mathematical and simulation methods. Appropriate mathematical models were adopted from the previous studies to evaluate the heat transfer characteristics and the transport properties of the novel nano-refrigerant. The analysis was carried out with the volume fraction of nano-sized CuO particles in R1234yf refrigerant ranging from 0.2 to 1% and the temperature varying from 0 °C to 65 °C. From the investigation, it is seen that the viscosity, thermal conductivity and density are augmented with nanoparticle inclusion. However, the specific heat capacity of the nano-enhanced refrigerant is diminished with intensify in the nanoparticles’ concentration. The heat transfer coefficient and pressure drop of the nano-refrigerant are enhanced by 45.36% and 35.69% respectively. There is a 3.91% average absolute deviation observed between the results obtained from the mathematical and simulation method.

Energy and Exergy Analysis of an Automobile Hybrid Ejector Refrigeration System Utilizing Its Exhaust Waste Heat

Abstract A major current focus of refrigeration and air-conditioning research is energy usage and environmental impact (e.g., the influence of refrigerants and air-conditioning systems on ozone layer depletion and global warming). The ejector-based refrigeration system is a technology that, it is hoped, can save power while using environment-friendly refrigerants to reduce any adverse effects on nature. The reduction of compressor dependency is the first and essential aim of this study; the second is to demonstrate the replacement of R134a with the new refrigerant R1234yf in motor vehicle air-conditioning systems, establishing the benefits of employing R1234yf in conjunction with a hybrid air-conditioning system. In such a system, the engine's exhaust gases are used to operate the ejector. A numerical model has been developed which estimates the ejector entrainment ratio at a specified spindle and primary nozzle exit position. A theoretical model using energy and exergy analysis illustrates the impact of hybrid systems on performance under different operating conditions (i.e., engine exhaust, ambient air, and evaporator temperatures). At a specified exhaust temperature, a detailed comparison has been conducted between a current air-conditioning system with R134a and the hybrid system with R1234yf. It was found that the R1234yf hybrid system reduced compressor energy consumption by 44.43% and operating exhaust heat levels by 12.79%. The coefficient of performance increased by 41.42%, while the exergetic efficiency reduced from 37.14% to 13.85%. Cooling capacity dropped by 12.73%. The hybrid air-conditioning system based on R1234yf demonstrated tremendous potential for improving vehicle air-conditioning system efficiency.

Vapor and Liquid (p-ρ-T-x) Measurements of Binary Refrigerant Blends Containing R-134a, R-1234yf, and R-1234ze(E).

The pressure-density-temperature-composition (p-ρ-T-x) data of binary refrigerant mixtures containing R-134a (1,1,1,2-tetrafluoroethane), R-1234yf (2,3,3,3-tetrafluoropropene), and R-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) were measured in both the vapor and liquid phases using a two-sinker, magnetic-suspension densimeter. The specific samples in this study comprised two compositions of approximately (0.3/0.7) and (0.7/0.3) mole fraction for each of the following three binary refrigerant blends: R-1234yf + R-134a, R-134a + R-1234ze(E), and R-1234yf + R-1234ze(E). Single-phase vapor densities were measured over a temperature range of (253 to 293) K and pressures from approximately (0.04 to 0.5) MPa. Single-phase liquid and supercritical densities were measured over a temperature range of (230 to 400) K and pressures up to 21 MPa; for refrigerant blends containing R-1234yf, the maximum pressure was limited to approximately 12 MPa. Overall relative combined, expanded (k = 2) uncertainties in density ranged from 0.043% to 0.418%, with an average uncertainty of approximately 0.06%. Here, we present measurement results, along with comparisons to available literature data and to default equations of state and mixture models included in REFPROP.

Simulasi Kinerja AC Split Menggunakan R32, R410A, R290, dan R1234YF

Air conditioning (AC) is the treatment of air to regulate temperature, humidity, cleanliness and comfortable conditions needed by humans in a room. The lecture room in the Mechanical Engineering building at Nusa Cendana University is a building that is quite busy with lecture activities and services related to students. Therefore, it is necessary to have an air conditioning system to maintain thermal comfort for students and lecturers who carry out activities. This research aims to analyze the performance of the cooling system using refrigerants R290 and R1234YF as alternative refrigerants to replace refrigerants R32 and R410A using CoolTools software version 1.01. The simulation is based on steady state conditions with the AC cooling load being 5.3 kW. The results of this simulation show that the performance of an air conditioning system that uses R290 and R1234YF as an alternative refrigerant can be used because it has a better performance coefficient than refrigerants R32 and R410A

Experimental Testing of a Water-to-Water Heat Pump with and without IHX by Using Refrigerants R1234yf and R1234ze(E)

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%.

Research on the field strength characteristics and the flammable area of refrigerants leakage into a confined space

Some target refrigerants used in refrigeration systems have various flammability. Once the flammable refrigerants leak into a confined space, it is easy to pose safety hazards. Moreover, the leakage refrigerants undergo continuous expansion and compression processes in the near field of the confined space, and the field strength of the refrigerants changes dramatically, which has an impact on the diffusion and the concentration distribution of the refrigerant in the far field of the confined space. The differences in the field strength and the flammable area for different refrigerants are largely determined by the thermophysical parameters of the refrigerants. Therefore, to better assess the hazards of refrigerant leakage, R717, R290, R161, R32, R152a and R1234yf were selected as the targeted leakage refrigerants in this paper, R744 and R134a were selected as the referenced refrigerants, the temperature, velocity and concentration fields of the refrigerants leaking into a confined space were studied, the influence of thermophysical parameters on the field strength of the refrigerants in the near field was further analyzed, and the flammable area formed in the space was explored. The results found that the temperature field was mainly affected by the density and the specific heat of the refrigerant. The velocity field was mainly affected by the density and viscosity of the refrigerant. The concentration field was mainly influenced by the density, viscosity and diffusion coefficient of the refrigerant. When the density was close, Schmidt number could be used to assess the influence of the viscosity and the diffusion coefficient on the concentration field. Under the same leakage pressure, the range of the flammable area formed by the leakage of R290 was the largest, followed by R161 and R152a, the flammable areas of R1234yf and R717 were very close, and the flammable area formed by R32 was the smallest.

A new approach for environmental analysis of vapor compression refrigeration systems: Environmental impact index

Vapor-compression refrigeration (VCR) cycles are used to transfer heat from a low-temperature environment to a high-temperature environment. To reduce harmful emissions, environmentally friendly refrigerants should be selected. Metrics like global warming potential and life cycle climate performance are used for environmentally friendly refrigerants. These metrics are independent of each other and are analyzed and evaluated separately. In this study, a new metric was proposed for the environmental analysis of VCR systems and named as environmental impact index (EII). EII defined for the first time in this research, includes the use of both energy, exergy, and low-emission renewable energy at the same time. Also, EII analysis of a cooling system using various refrigerants was performed for all cities of Türkiye. In the case of using R134a, R1234yf, and R1234ze refrigerants in the cooling system the cities with the highest and lowest EII values of the cooling system are Ardahan and Şanlıurfa, respectively. The EII of R134a, R1234yf, and R1234ze (E) for Şanlıurfa are 49.79, 51.81, and 49.75, respectively. The EII of R134a, R1234yf, and R1234ze (E) for Ardahan are 73.75, 75.13, and 73.13, respectively. It was concluded that when choosing refrigerants for VCR systems, attention should be paid not only to the GWP ratios of refrigerants, but also to energy and exergy performance, and energy options with lower emissions.

Boiling heat transfer of binary and ternary mixtures in multiple rectangular microchannels

In this study, the boiling heat transfer of binary and ternary refrigerant mixtures in a horizontal multiport tube with multiple rectangular microchannels was investigated. The influences of the mass velocity, vapor quality, and heat flux on the heat transfer were evaluated for near- and non-azeotropic mixtures of R410A, R32/CF3I, R32/R1123, R32/R1234yf, R1123/R32/R1234yf, and CO2/R32/R1234yf. The obtained results were compared with those of pure refrigerants R1234yf and R32. For R1234yf at low mass velocity, the flow patterns were estimated as intermittent (plug) and slug-annular flows with an extremely thin liquid film. The heat transfer coefficient decreased when the heat flux was increased because dry patch areas formed and expanded on the sides of the noncircular microchannel. The near-azeotropic mixtures with small temperature glides exhibited heat transfer characteristics similar to those of the pure refrigerant. Conversely, the heat transfer coefficients deteriorated slightly under lower mass velocities. The heat transfer coefficients of binary and ternary mixtures with larger temperature glides were significantly different from those of pure refrigerants and near-azeotropic mixtures; they decreased with decreasing mass velocity owing to mass diffusion resistance. The heat transfer coefficients of binary mixtures with large temperature glides decreased monotonically as the mass velocity decreased, and the heat transfer noticeably deteriorated at lower mass velocities. The heat transfer model was developed for rectangular microchannels by considering the heat transfer contributions of thin liquid film evaporation due to surface force, forced convection, and nucleate boiling. Moreover, this model considers the flow pattern of multiple microchannels, heat transfer degradations due to dry patches and mass diffusion resistance, and dryout incipience quality. The results of the present model agree well with the heat transfer coefficients, including those of binary and ternary mixtures, in the pre- and post-dryout regions with a mean percentage error of 3.1%.

Alternative CO2-based blends for transcritical refrigeration systems

The extensive use of CO2 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, CO2-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 CO2. This manuscript analyses five binary mixtures of CO2 with the refrigerants R32, R152a, R1234yf, R1234ze(E) and R1270, determining the optimal mixture composition for maximising the COP of a CO2 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 CO2/R32 (81/19% in mass) and CO2/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.

Investigation on absorption performance of R134a and R1234yf refrigerants using HMIM-based ionic liquids

In order to recover and reuse refrigerants that accelerate global warming, it is necessary to absorb refrigerants and separate mixed refrigerants. Therefore, this study evaluated the performances of 1-hexyl-3-methylimidazolium (HMIM)-based ionic liquids [HMIM][BF4], [HMIM][PF6], and [HMIM][Tf2N] for the selective absorption of R134a and R1234yf refrigerants. According to the experimental results, refrigerant absorption depended on the viscosity of the ionic liquid, the molecular structure and temperature of the refrigerant, and the pressure. As Henry's law constant decreased, the refrigerant-absorption performance of the HMIM-based ionic liquids increased. In addition, [HMIM][Tf2N] and [HMIM][BF4] exhibited the highest absorption performance of refrigerants per hour at 300 and 400 kPa, respectively. R134a demonstrated better refrigerant-absorption performance than R1234yf, which indicates the possibility of selective separation using ionic liquids.

Experimental Investigation of InTube Condensation of HFO-1234yf

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.

Experimental operating range evaluation of flat-plate pulsating heat pipes for high-heat flux automotive power electronics cooling

Flat-plate pulsating heat pipes are a promising future technology to passively increase the power density of power electronics in mobile applications by means of a more efficient thermal management. However, in the design phase, it is not known how different thermal boundary conditions are affecting the operation range of a pulsating heat pipe. To experimentally assess this dependency, the present work aims to evaluate the performance of a flat-plate pulsating heat pipe for electric mobility and different operating conditions. To this purpose, a flexible test section was designed allowing to raise different heating and cooling conditions. A novel array of multiple hotspots was employed which realistically represents a power semiconductor layout. This way, a local heat flux of up to 200W/cm2 was introduced to the pulsating heat pipe. In the condenser section, the coolant temperatures were varied between 10°C and 60°C, representing real conditions of a driving cycle. The investigated aluminum pulsating heat pipe consists of 22 rectangular channels and two different newest generation refrigerants R1233zdE and R1234yf were used as working fluids. Based on the new experimental evidence, our previously published thermal resistance model was adapted. A posteriori comparison with previous calculations confirms the validity of the numerical assumptions and shows a good agreement with the obtained results. For the first time, our investigation shows that pulsating heat pipes can robustly achieve heat flux densities above 100W/cm2 at conditions representative for automotive electronics applications. The real implementation potential was demonstrated, as an considerable 5 to 11 times higher effective thermal conductivity than solid aluminum was obtained depending on the integration concept.

Condensation of R1234yf in a plate heat exchanger with an offset strip fin flow structure for electric vehicle heat pumps

The energy-efficient plate heat exchanger (PHE) and refrigerant R1234yf, which has a low global warming potential (GWP), can be used to realize an energy efficient heat pump (HP) system for electric vehicles (EV), extending their driving range. Therefore, the characteristics of R1234yf in an offset-fin strip (OSF) flow-structured PHE are critical for heat-exchanger design. This study investigates the condensation heat transfer coefficient (C-HTC) and two-phase frictional pressure drop (2P-FPD) of R1234yf during condensation in an OSF flow-structured PHE under various operating conditions. First, a modified Wilson plot method was used to determine the multiplier (C) and Reynolds number exponential (n) for the coolant side as −0.426 and 0.494, respectively. When the heat flux (q), average vapor quality (xa), and mass flux (G) increased, the C-HTC increased, whereas it decreased with saturation temperature (Tsat). Despite the force-convective condensation flow regime, the C-HTC increment was minimal with G at lower xa owing to the lesser significance of the shear effect. Additionally, the 2P-FPD was unaffected by q but increased considerably with an increase in xa and G and a decrease in Tsat. Based on the current experimental database, empirical correlations for forecasting friction factor and Nusselt number were developed with a 91% predictability.