Environment-friendly Refrigerant Research Articles

Numerical and Performance Analysis of R290 Heat Pump Driven Air Conditioning System for Heating and Cooling

The demand for heating and air conditioning is rising due to rapidly changing climatic conditions. The market for heat pumps and air conditioning systems is seeing a steady increase in low global warming potential. There is a growing need to use environment-friendly refrigerants. Contemporary Refrigerants (HCFCs) such as those found in heat pump air conditioning systems have the potential to cause global warming and ozone depletion. Using more environmentally friendly refrigerants, including hydrocarbon and blend refrigerant mixtures, is one way to lower Global Warming Potential (GWP) and Ozone depletion potential. This study examines the performance of several alternative refrigerants, including R32, R134A, R410A, R22 and R290. To examine the performance of R290, theoretical and simulation results are compared for various refrigerants while taking into account several performance parameters, including the refrigerant energy efficiency ratio, mass flow rate, coefficient of performance, cooling capacity and compressor work for One Ton of Refrigeration (1TR) air conditioners. One player with a very low GWP is R290. However, the only drawback is that it can catch fire and is hazardous to use in split-type commercial heat pump air conditioning applications. The environmental and thermo physical properties of R290 are significantly better than those of other materials, according to theoretical and simulation studies utilising Cool Pack software, hence it is a viable replacement.

Thermo-economic investigation on organic Rankine cycle based solar integrated ejector-trigeneration system (EORC-CCHP) for Indian climate

A novel solar integrated ejector-based combined cooling, heating, and power (EORC-CCHP) system based on an organic Rankine cycle is proposed to provide sustainable multiple outputs to meet energy demand. A comprehensive energy and exergy analysis is performed to evaluate the system's performance using six different environment-friendly refrigerants, such as R1233zd, R245fa, R236fa, R142b, R600a, and R124. A parabolic trough collector (PTC) distributes the solar energy to the boiler as a heat source. To study the system's performance at sub-zero evaporator temperatures, the primary flow from the ORC turbine's first-stage expansion is extracted and sent through an ejector refrigeration cycle for the required cooling effect. The remaining refrigerant is expanded across the turbine with a targeted power output of 5 kW and is sent for heat recovery across the heater. Among the refrigerants studied, R600a, R124, and R1233zd demonstrated the highest refrigeration COP of 0.58, system COP of 1.69, and exergy efficiency of around 68.26%. However, due to the lower critical condenser temperatures of R124 and R1233zd makes them obsolete due to negative pressure, R600a is observed as the optimal working fluid. The PTC system demonstrates diurnal variations, with a combined peak energy output of 31.3 kW in May for the Hyderabad climate. Exergy analysis shows that the primary sources for exergy destruction are the PTC system, boiler, and ejector, with destruction rates of 51%, 20.1%, and 22.1%, respectively. The boiler is the main source of exergy destruction cost, with a cost of 0.18 $/h, and the condenser and PTC exhibit the highest total cost rates. The environmental impact of the PTC system is assessed, with July showing the highest environmental effect to unit useful exergy of 71.54 mPts/GJ.

Numerical investigation of entropy generation for flow boiling of R600A in the corrugated U-bend tube heat exchangers

The development of compact and efficient corrugated heat exchangers for refrigeration and air conditioning systems is reliant upon thermal-hydraulic performance, which is quantifiable in terms of entropy generation. Hence, this study presents the generation of entropy analysis for flow boiling evaporation with an environment-friendly refrigerant (R600a) in the novel design of corrugated (outward circular ribs corrugated, inward circular ribs corrugated, outward triangular ribs corrugated, and inward triangular ribs corrugated) U-bend tube exchangers. The performance of the corrugated tube heat exchangers has been reported in comparison with the smooth U-bend tube heat exchanger. The numerical calculations were executed using CFD code for various masses ranging from 100 to 400 kg/m2s at the saturation temperature and vapor quality of 20 °C and 0.2 respectively while 15 kW/m2 heat flux was applied on the external surface of the straight tubes. The results revealed that the entropy generation increases as the mass flux increases with the inward circular and triangular ribs corrugated tube having the highest generated entropy followed by the outward circular and triangular ribs corrugated and then the smooth tube with the least entropy generation. In reference to smooth tube for the mass flux of 100 kg/m2s, the entropy generation for inward circular and triangular ribs corrugated increased by 46.88% and 130.93% respectively while the outward circular and triangular ribs corrugated increased by 18.35% and 39.26% respectively. Lower dimensionless Bejan numbers were obtained in the corrugated tubes with respect to mass fluxes compared to the smooth tube. The fluid flow irreversibility contribution to the overall entropy generated was higher in the corrugated tubes due to the corrugation surface which causes swirl mixing. The results of the numerical calculations were confirmed and corresponded with those established in the literature.

Energy, exergy, environmental and exergoeconomic (4E) analysis of an ultra-low temperature cascade refrigeration system with environmental-friendly refrigerants

To ensure the efficacy of some special vaccines, the ultra-low temperature storage below −80 °C is strictly required and the classical cascade refrigeration system has a good application prospect in the production, storage, transportation and distribution of COVID-19 vaccines. Previous investigations are mainly focused on the thermodynamic performance of cascade refrigeration cycles (CRSs) to generate low temperature, and the impact of cascade refrigeration cycles on environmental and exergoeconomic aspects is few involved. In this paper, an energy-exergy-environmental-exergoeconomic (4E) analysis model was built to investigate the comprehensive performance of an ultra-low temperature cascade refrigeration system. Eight environmental-friendly refrigerant pairs, including R290-R170, R290-R1150, R717-R170, R717-R1150, R1270-R170, R1234yf-R170 and R1234yf-R1150, were chosen and the associated refrigeration performance was compared. The results show that the optimal refrigerant pair is propane-ethane (R290-R170). Compared with HFC refrigerant pair R404A-R508B CRS, R290-R170 CRS could improve the COP by 5.94%, save 5.68% power consumption, reduce 29.67% carbon dioxide emission and decrease 5% exergy economic cost. This work is significant to select environmental-friendly nature refrigerants, enrich understanding of comprehensive performance of cascade refrigeration system and enhance depth research on ultra-low temperature refrigeration.

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

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

Designing of Evaporator Length in Very Low Temperature Chest Freezer by using Environmentally Friendly Refrigerant R290

Chest freezers generally use R600a or R134a as working fluids. When using R600a, the minimum cabin temperature is only -10oC, whereas when using R134a, it can reach -25oC. The purpose of this study is to calculate the evaporator length of a chest freezer that uses R290 as a refrigerant so that its cabin temperature can reach below 35 oC, lower than the cabin temperature of a typical chest freezer. Calculation of the evaporator pipe length is done using the forced convection heat transfer equation to calculate the heat transfer coefficient inside the evaporator pipe and natural heat transfer to calculate the heat transfer coefficient outside the evaporator pipe. Based on the calculations, the chest freezer has a compressor capacity of 200 W, an evaporator length of 3.57 m, and a diameter of 3/8 inch or 9.52 mm. The test results show that the temperature of the chest freezer cabin can reach -36oC in the 36th minute with a cooling capacity of 289 W, while the input power and COP are 198 watts and 1.46, respectively. Compared to R134a, the use of R290 is more advantageous. In addition to lower cabin temperatures, it is also much more environmentally friendly, because the GWP (global warming potential) value of R134a is much higher than that of R290. It means that the use of R290 as a working fluid in the chest freezer will significantly reduce emissions of gases that cause global warming.

Parametric analysis and multi-objective optimization of a heat pump dryer based on working conditions and using different refrigerants

Considering Heat pump dryers are extensively used in the food industry, evaluating and optimizing their performance can be beneficial. Therefore, a comprehensive model is presented in this study using for waste food with considerations of energy, exergy, and exergoeconomy. Several influential parameters, such as evaporator and condenser temperatures, heat pump capacity, dry and wet-basis moisture content, along with the product mass and refrigerant types, are considered in the investigation. Five environmentally-friendly refrigerants of, R134a, R1234yf, R1234ze, R717, and R152a, are used as the working fluid of the heat pump. The parametric study shows that evaporator and condenser temperatures and heat pump capacity have significant effects on the heat pump COP, exergy efficiency, drying time, and cost of dried product. Hence, assuming these four objective functions, a multi-objective optimization model based on the TOPSIS method is presented. According to this, the optimal point of the system is found at the evaporator and condenser temperatures of 10.32 °C and 69.68 °C, respectively. Results of the refrigerant analysis demonstrate that although R717 has the best energetic performance, using R1234yf results in the shortest drying time and lowest cost of dried product.

Effect of system configuration on the performance of a hybrid air conditioning system based on R-1234yf

The study presents theoretical results on a hybrid air conditioning system in which the sensible and latent loads are separately managed. The problem studied is significant in view of the growing demand for air conditioning systems globally, and also due to the adverse impact of these systems on global warming. In order to reduce the environmental impact of the air conditioning systems, this study proposes a hybrid system comprised of a vapour compression heat pump and a desiccant wheel. Due to restrictions on high global warming potential (GWP) refrigerants, R-1234yf, a low GWP refrigerant is considered as the working fluid for the heat pump. An enthalpy wheel is included to reduce the ventilation load on the system. The proposed hybrid system’s performance is evaluated using the first and second laws of thermodynamics and psychrometric principles. Results are compared with that of a conventional air conditioning system. Based on the calculated values of component and process wise irreversibility, further modifications to the hybrid system are proposed. These modifications consist of addition of a liquid-to-suction heat exchanger and use of a split condenser. Results show that depending upon the latent load on the conditioned space, the compressor power input can be reduced by as much as 47% using the proposed hybrid system. Compared to the conventional system, the modified hybrid system shows excellent performance under both high as well as low latent loads, whereas the simple hybrid system performs very well in applications involving high latent loads. The work presented is novel as it considers both first and second laws of thermodynamics to arrive at an optimum hybrid system configuration using an environment friendly refrigerant. It is expected that the study will be useful in the development of energy efficient and environment friendly air conditioning systems that operate equally well under low and high latent loads.

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.

A parametric study and performance investigation of thermoelectric refrigeration system using computational fluid dynamics

Global commercial market forecasted around 45 billion US dollars for refrigeration equipment in 2021. Currently used refrigerants have high global warming potential (GWP); hence, environment-friendly refrigeration system using the Peltier effect is being considered for this research. The thermodynamic refrigeration system has a low coefficient of performance (COP), when compared to chlorofluorocarbon (CFC) and hydrofluorocarbon (HCFC) refrigeration systems. The design of various models of the thermoelectric refrigerator (TER) is created using ANSYS workbench. Each new design is analysed with computational fluid dynamics (CFD) analysis tool by altering insulating materials such as nickel with aluminium foil and polyurethane foam in airflow streamline of thermoelectric refrigeration. Temperature differences obtained between 7.5 and 9.4 °C are tabulated after each run using the finite volume method. Optimization of inner design and insulation material is done by using computational fluid dynamics analysis in the ANSYS FLUENT software. The results of sharp edge design have proved better when compared to partially round edge design and fillet design, 7.85 °C for the cold region and 54.85 °C for the hot region. Further research is expected using the multistage Peltier module and smart temperature control unit to improve the COP of the TER system.

Exergoeconomic and exergoenvironmental based multi-criteria optimization of a new geothermal district heating system integrated with thermal energy storage driven heat pump

In this study, a new geothermal district heating system, which includes a heat pump (HP) system driven by thermal energy storage (TES) unit, was optimized throughout the multi-criteria decision making analysis named efficiency analysis technique with output satisficing (EATWOS). In this regard, the objective functions were chosen as exergoeconomic and exergoenvironmental indicators varying with the handled designs. 111 different designs formed considering different working parameters and fluids in this aim. Three environment-friendly refrigerants according to their thermal behaviour (wet, dry, and isentropic types) and suitable phase change materials (PCM) according to the design conditions were evaluated. The designed system was evaluated by energy, exergy, exergoeconomic, and exergoenvironmental tools to determine the objective functions. As conclusion, Case 108 with the refrigerant of R1234ze and PCM of RT70HC was determined as the best design. The sustainability index, exergoeconomic factor, exergoenvironmental factor, relative cost, and relative exergoenvironmental impact of this optimal case were determined as 1.24, 0.002583%, 0.0540%, 460.85%, and 649.50%, respectively. For this case, the energy and exergy efficiencies of the system were determined as 74.56% and 19.17%, respectively. In comparison to conventional system, a decrease of 38.86% in relative exergoeconomic cost (r) and a decrease of 19.21% in the relative exergoenvironmental impact (rb) were achieved.

Thermodynamic Analysis of an Innovative Cold Energy Storage System for Auto-Cascade Refrigeration Applications

The cooling capacity needed by ultra-low temperature apparatus cannot be reached economically with a single vapor compression refrigeration cycle due to the constraint of the high compressor pressure ratio. The auto-cascade refrigeration cycle is a good alternative. In this work, a novel concept that applies the principle of the auto-cascade refrigeration cycle to store cold energy is conducted. The environment-friendly refrigerants of R600a/R290/R170 zeotropic mixtures are used to study the performance of the modified auto-cascade refrigeration cycle (MACRC) as an alternative for cold-energy applications. The simulation results show that a cooling capacity of 500 W can be provided below −60 °C. The mixture with a mass fraction of 0.25/0.35/0.40 yields a COP of 0.695 and an exergy efficiency of 0.262 at −66 °C. The performance of the MACRC system was investigated at an ambient temperature of 20 to 40 °C for indoor small-scale applications. It is concluded that the performance would be improved by decreasing the ambient temperature. The results of the work should be helpful for the design and optimization of auto-cascade systems.

Investigations on Solar Powered Vapour Absorption Refrigeration based Air Conditioning

A solar-operated vapor absorption refrigeration cycle is environment-friendly refrigeration system that holds the potential to be used for refrigeration and air conditioning systems. Such a system requires a solar concentrator to run the vapor absorption refrigeration cycle using LiBr-H2O-based refrigeration/air conditioner for small capacity applications. With the solar-powered pumping process, this refrigeration system becomes completely free from electricity requirements. However, the limitations of all time solar radiation availability, low-pressure maintenance requirement of the LiBr-H2O system, low efficiency, and low COP as compared to other vapour compression refrigeration based air conditioning system are the key deterrents. In the present study, the modeling and analysis of various components used in the proposed arrangement of solar vapor absorption refrigeration - air conditioning system has been carried out to improve the performance It is seen that altering the geometrical property of the bubble pump, as well as heat input through a solar concentrating collector, use of hydrogen as a third fluid increases the rate of evaporation which in turn increases the cooling effect as well as COP of the cycle. At 54% concentration of LiBr and 4.5kW heat input, the COP of the proposed layout is found to be 0.61.

Technical assessment of novel organic Rankine cycle driven cascade refrigeration system using environmental friendly refrigerants: 4E and optimization approaches.

Hydrocarbons are a promising working fluid for organic Rankine cycles and refrigeration systems that have gained increasing attention in recent decades as a replacement for the currently used higher global warming potential fluids. A novel standalone cascade refrigeration system (CRS) has been developed in this study for simultaneous ultra-low temperature cooling and heating production to medical applications most suitable for rural and power outages. Using the energy utilization factor (EUF) metrics, neopentane was chosen as the working fluid for the organic Rankine cycle (ORC) system among the selected hydrocarbon (HC) refrigerants. The standalone ORC-CRS system performance was investigated in terms of cooling and heating capacity, EUF, exergy, and environmental metrics by varying both ORC and CRS key temperature parameters. The exergy destruction of individual components was evaluated, and it was found that the ORC evaporator has the highest exergy destruction, followed by the expander. The highest EUF and exergy efficiency for a combined ORC-CRS system was about 0.64 and 38%. The maximum cooling and heating capacity of novel standalone CRS system was achieved by 70kW and 225kW respectively at a typical operating condition. At a higher ORC evaporation temperature, the exergy efficiency of the ORC-CRS system is decreased, leading to reduction in SI. The standalone ORC-CRS system at ORC evaporator temperature of 150°C achieved the maximum CO2 emission tax savings of $ 6.4 × 107 over a 15-year lifetime period. The total annualized cost index of the combined cooling heating system is in the range between 35 and 60 $/h for the variable operating condition. Non-dominated sorting genetic algorithm II (NSGA-II) method was used to conduct the multi-objective optimization analysis, and the technique for order of preference by similarity to ideal solution (TOPSIS) method used to found the optimal point, which had the following values of TAC 42.22 $/h and exergy efficiency was around 46.10%.

Vapor-liquid equilibrium measurements and models for the ternary mixtures of R1234yf + R32 + R125 and R1234yf + R32 + CO2

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 + CO2 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 + CO2 ternary mixture. Experimental results and model calculations showed that both the ternary mixtures were zeotropic.

Experimental and Theoretical Investigations of a Ground Source Heat Pump System for Water and Space Heating Applications in Kazakhstan

The ground source heat pump heating system is considered as one of the best solutions for the transition towards green heating under the continental climate conditions like Kazakhstan. In this paper, experimental and theoretical investigations were carried out to develop a ground source heat pump-based heating system under the weather conditions in Kazakhstan and to evaluate its thermodynamic performance. The water-to-water heat pump heating system, integrated with a ground source heat exchanger and used refrigerant R134a, was designed to provide hot water to meet the requirements for space heating. The predicted values of the coefficient of performance and the experimental results were found to be in good agreement within 6.2%. The thermodynamic performance of the system was also assessed using various environment-friendly refrigerants, such as R152a, R450A, R513A, R1234yf and R1234ze, as potential replacements for R134a. Although R152a is found to be a good alternative for R134a in terms of coefficient of performance and total equivalent warming impact, its flammability hinders its application. The heating system using refrigerants R450A, R513A, R1234yf and R1234ze shows 2–3% lower coefficient of performance than that of R134a. The highest exergy destruction is found to be attributed to the compressor, followed by the expansion valve, evaporator, and condenser. Considering their low flammability and low environmental impact, R450A, R513A, R1234yf and R1234ze are identified as valuable replacements for R134a.

Experimental study of propane heat pump system with secondary loop and vapor injection for electric vehicle application in cold climate

In order to solve the problem that the driving range of electric vehicles (EVs) is reduced due to heating in cold climate, and the traditional R134a needs to be replaced by more environmentally-friendly refrigerants, a novel solution of coupling the secondary loop and vapor injection technology (SL + VPI) was proposed. Although propane has high flammability, it is still considered a promising alternative because of its low global warming potential (GWP), high performance, and less charge mass. The impacts of VPI technology, ambient temperature, waste heat recovery power, compressor speed, indoor inlet air flow rate, and charge mass on the heat pump system performance have been experimentally studied. In addition, the heating performance and driving range improvement of different heat pump systems were compared. The results show that at −20 °C ambient temperature, the propane SL + VPI system was second only to CO2 direct heat pump system; its heating performance was 33.3–37.4 % greater than the propane direct heat pump.

An Overview of Environment-Friendly Refrigerants for Domestic Air Conditioning Applications

Low global warming potential (GWP) refrigerants for the next-generation air conditioning systems have been investigated with target domestic applications. High-GWP refrigerants are mostly used in climate control applications such as heating, ventilation and air conditioning (HVAC) and refrigeration systems. The majority of refrigerants are responsible for significant environmental issues such as ozone layer depletion and global warming. The Montreal Protocol and the Kyoto Protocol have been implemented to address such issues. In the meantime, authorities in many countries have taken the initiative to phase out the usage of environmentally harmful refrigerants in vapor compression refrigeration systems. Following the global warming mitigation scheme by many signatory countries, research interest has been focused on finding alternative refrigerants with low or ultra-low GWP. This study considered the research trend and development of low-GWP refrigerants while examining system performance, safety issues, and the equivalent environmental impact as the critical assessment parameters. Here, the focus is primarily set on the potential of refrigerant blends (HFCs + HFOs) where the GWP value of 300 is set as the threshold value. Targeted for domestic heat pump systems, the performance of such systems using various refrigerant blends is collated and discussed. Many blends offer innovative drop-in replacements for R410A-conforming F-gas regulations. The technical difficulties and realistic remedies for the existing refrigerants are also discussed.

Flammability inhibition effect assessment with mildly flammable refrigerant and inert gases on difluoromethane

The flammability of refrigerants seriously affects the safe use of new generation environment-friendly refrigerants. Mixing inert gas or mildly flammable refrigerants with other flammable refrigerants has a specific inhibition effect, but the mechanism is still unclear. The burning velocity inhibition effect was theoretically studied by analyzing the influence of working fluids such as R1234yf and CO2 on the burning velocity of R32 with and without water and analyzing the reaction pathways. Results have shown that a small amount (5% molar concentration) of weakly flammable R1234yf has a more obvious inhibition effect on the burning velocity of R32 than the same amount (5% molar concentration) of inert gas CO2; when the mole fraction of the additives is large (50% mole concentration), the result is the opposite. The presence of water slightly increases the burning velocity, and the increase of the burning velocity is affected by the ratio of fluorine. Through the reaction path analysis, the reactive group CHF3 after thermal decomposition of R1234yf reacts with R32, which changes the reaction path of R32 directly, reduces the rapid reaction of R32, and reduces the initial burning velocity of combustion.

Energy analysis and performance comparison of transcritical CO2 supermarket refrigeration cycles

Using carbon dioxide as a refrigerant gains importance as a result of restrictions applied to high-GWP (Global Warming Potential) refrigerants. Although CO2 is an environment-friendly refrigerant, its low critical temperature and high operating pressure lead to high energy consumption, especially in commercial refrigeration. As a result, research and improvements are being made to reduce the energy consumption of transcritical CO2 refrigeration cycles. This paper presents thermodynamic analysis and pressure optimizations to obtain maximum performance for transcritical booster, parallel compression, and ejector expansion supermarket refrigeration cycles. Effects of different operation conditions were also investigated and cycles were compared to each other in terms of performance. It was obtained that up to 47% Coefficient of Performance (COP) improvement can be achieved using ejector expansion cycle with the help of expansion work recovery in the ejector. It was also shown that ejector expansion cycle outperforms other CO2-only cycles without ejector in all conditions.