Alternative Refrigerants Research Articles

A REVIEW on PRIMARY ENERGY RATIO VALUES of GAS ENGINE DRIVEN HEAT PUMP SYSTEMS

This study reviews the primary energy ratio values of gas engine driven heat pump systems in order to compare gas engine driven heat pump systems among themselves or with heat pump systems using different energy sources in terms of efficiency values. A comprehensive literature review of studies investigating primary energy rates of gas-driven heat pump systems have been presented. The primary energy ratios obtained in the studies on gas driven heat pump systems were determined and tabulated. In addition, waste heat recovery rates in these systems were also investigated. Studies in the relevant field are grouped as experimental and theoretical. Additionally, the differences in the examined system structures are stated and primary energy ratios are presented. Primary energy rates of systems with and without heat recovery were examined. There is no compilation study on the subject in the literature. The calculation methodology used and the obtained values for calculating the primary energy rates of gas-driven heat pumps are presented. Thus, the energy efficiency and environmental evaluations of the examined systems are presented in the light of the literature. In addition, which refrigerants were used in the studies conducted in the literature are presented. Recommendations are provided on choosing alternative and sustainable refrigerants.

Numerical simulation study of boiling heat transfer of R290 flow in horizontal microtubes

Abstract R290 is considered to be an excellent alternative refrigerant for domestic air conditioners in the future. In this paper, CFD numerical simulation was used to obtain the flow field distribution of R290 in a micro-fine circular tube with an inner diameter of 2mm under a specific range of working conditions, and the effects of saturation temperature, mass flow density, heat flow density and tube type on the boiling heat transfer characteristics of R290 tube were investigated. The results show that the boiling heat transfer coefficient increases with the increase of saturation temperature, and the maximum value of the heat transfer coefficient increases by 8.1% when the saturation temperature increases from 284K to 286K. The boiling heat transfer coefficient increases with the increase of mass flow density, and the maximum value appears in the medium dryness range. The boiling heat transfer coefficient in the tube increases and then decreases when the heat flow density increases from 10 kW/m2 to 20 kW/m2 and increases faster at high heat flow density conditions. In addition, compared with the circular tube, the boiling heat transfer coefficient in the elliptical tube with an aspect ratio of 1.56 increases by 2.78% for R290 under the same flow area.

Analysis of Automotive Air Conditioning System Performance with Alternative Refrigerants to R-134a

This work analyzed the performance of the automotive air conditioning system, operating with several alternative refrigerants to R-134a. For this, a thermodynamic model of the automotive vapor compression cycle was implemented to determine the COP of the system, the refrigeration capacity, and the consumption of the compressor. The model considers the compressor rotation speed, ambient temperature, cabin temperature, air speed in the condenser, and volumetric airflow in the evaporator as operating parameters. The refrigerants chosen for the analysis were R-152a, R-1234yf, R-290, R-410A, and R-32. The simulation was carried out with climatic data from the city of Riobamba, and temperatures inside the cabin were measured experimentally. The study shows that the refrigerant R-152a has a COP 10% better than R-134a and could be an alternative for direct replacement of refrigerant. On the other hand, R-1234yf presented a COP 9% lower than that of R-134a, which requires adjustments in the sizing of components to provide the same cooling capacity as R-134a. Finally, R-290, R-410A, and R-32 refrigerants have lower performance and higher compressor consumption. Keywords: automotive air conditioning, vapor compression cycle, COP, cooling capacity, refrigerants. Resumen En este trabajo se analizó el desempeño del sistema de aire acondicionado automotriz operando con varios refrigerantes alternativos al R-134a. Para ello, se implementó un modelo termodinámico del ciclo de compresión de vapor automotriz para determinar el COP del sistema, la capacidad frigorífica y el consumo del compresor. El modelo considera como parámetros de funcionamiento la velocidad de giro del compresor, temperatura ambiente, temperatura del habitáculo, velocidad del aire en el condensador y flujo volumétrico del aire en el evaporador. Los refrigerantes escogidos para el análisis fueron el R-152a, R-1234yf, R-290, R-410A, y el R-32. La simulación se realizó con datos climáticos de la ciudad de Riobamba y temperaturas del interior del habitáculo medidas experimentalmente. El estudio muestra que el refrigerante R-152a presenta un COP 10% mejor que el R-134a, pudiendo ser una alternativa para un remplazo directo de refrigerante. Por otro lado, el R- 1234yf presentó un COP 9% menor que el del R-134a, con lo cual se requieren ajustes en el dimensionamiento de componentes para proporcionar la misma capacidad de refrigeración que el R-134a. Finalmente, los refrigerantes R-290, R-410A y R-32 presentan un menor rendimiento y mayor consumo de compresor. Palabras Clave: aire acondicionado automotriz, ciclo de compresión de vapor, COP, capacidad frigorífica, refrigerantes.

Thermodynamic Comparative Analysis of Cascade Refrigeration System Pairing R744 with R404A, R448A and R449A with Internal Heat Exchanger: Part 2—Exergy Characteristics

The cascade refrigeration systems (CRS) used in hypermarkets and supermarkets, which are used by many people, have been employing R744 for the low-temperature cycle (LTC) and R404A for the high-temperature cycle (HTC) due to environmental and public safety issues. However, the use of R404A is limited due to its high GWP, and therefore research on alternative refrigerants is necessary. Nevertheless, there is no detailed study in the literature that compares and analyzes the three refrigerants for practical design by applying R744 for LTC and R404A, R448A, and R449A for HTC in CRS. Therefore, this study aims to provide data for the practical detailed design of an alternative system to R744/R404A CRS. Under standard conditions, we analyzed how the exergy destruction rate (EDR) and exergy efficiency (EE) of the system and the EDR of each component change when the important factors affecting CRS (degree of superheating (DSH), degree of subcooling (DSC), and internal heat exchanger (IHX) efficiency of HTC, DSH of LTC, condensation temperature (CT), evaporation temperature (ET), cascade evaporation temperature (CET), and temperature difference of CHX) are varied over a wide range. The main conclusions are as follows. (1) Under the given constant conditions, the smallest change in system EDR based on R448A is DSH of HTC (decreased by 0.07–0.1 kW), followed by IHX of HTC (decreased by 0.12–0.3 kW), DSH of LTC (increased by 0.19–0.25 kW), DSC of HTC (decreased by 0.59–0.69 kW), temperature difference of CHX (increased by 1.57–1.83 kW), CET (decreased and then increased by 0.67–4.43 kW), CT (increased by 1.49–3.9 kW), ET (decreased by 2.39–4.61 kW). (2) The highest change rate of system EE based on R448A is CET (increased and then decreased by 1.38–8.28%), followed by temperature difference of CHX (decreased by 2.96–3.16%), ET (increased and then decreased by 0.63–2.75%), DSC of HTC (increased by 1.26–1.34%), CT (increased and then decreased by 0.24–1.12%), IHX of HTC (increased by 0.11–1.02%), DSH of LTC (decreased by 0.35–0.49%), and DSH of HTC (increased by 0.14–0.19%).

Study on the impacts of refrigerant leakage on the performance and environmental benefits of heat pumps using R513A as replacement of R134a

The escalating threat of global warming has highlighted the imperative to address the greenhouse effect. R513A is recognized as a viable substitute for R134a, providing a lower global warming potential (GWP) while preserving similar thermodynamic properties. However, refrigerant leakage is one of the common faults in heat pump equipment. For industrial heat pumps, refrigerant leakage can make the system less stable and affect normal industrial production, while long-term leakage can also affect the carbon emissions of the industry. When substituting refrigerants, it is crucial to consider not only their distinct properties under typical operating conditions but also the stability and environmental impact of the alternative refrigerant in cases of leakage. This paper focuses on experimentally evaluating the impact of using R513A to replace R134a on the performance of refrigeration systems under the condition of rapid refrigerant leakage. Then the life cycle climate performance evaluation (LCCP) theory is used to assist experimental results in evaluating the carbon footprints of R513A and R134a systems at different annual leakage rates. The results show that R513A has better stability than R134a when responding to rapid refrigerant leakage. This paper determines the changes in annual electricity consumption and indirect emissions under several annual leakage rates and finds that the impact of leakage on indirect emissions is also not negligible. During the utilization phase of the equipment, when leakage was taken into account, the carbon emissions of the R134a system were higher.

Research on the characteristics of photovoltaic-driven refrigerated warehouse with ice storage in field under weather and load variation

The field photovoltaic refrigerated warehouse works well in pre-cooling and refrigerating fruits and vegetables in remote areas. Thus, it is crucial to ensure its long-term stable operation, particularly under the dual challenges of fluctuating solar energy supply and the unstable energy consumption required for load variation. This paper investigates the operational characteristics of a 1.5-ton photovoltaic-driven refrigerated warehouse with ice storage under varying loads and weather conditions. Results indicate that the average cooling time of the material was 26 h, under the condition of continuous material inflow into the warehouse. Additionally, 26 kg of ice were produced per day per kilowatt of solar panel capacity. Energy requirements of the device for 1.1 nights match its daily ice production. Furthermore, a maximum COP of 0.34 was achieved under photovoltaic drive. The internal temperature of the load was effectively maintained within the range of 3–4 °C, even during consecutive overcast and rainy weather. Based on this, an 8-ton field photovoltaic-driven refrigerated warehouse with ice storage was constructed. These studies provide an effective alternative refrigeration solution for remote regions, addressing their cooling needs efficiently.

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.

Energy, exergy, economic and environmental studies on a nonflammable eco-friendly mixture for efficient heating in cold regions

As a compelling alternative to fossil fuel combustion, air-source heat pumps face challenges in inefficiency, flammability, and pollution when operated at low ambient temperatures. To address the demand for safe, eco-friendly and efficient heating during wintertime, this work is devoted to exploring a novel refrigerant for air-source heat pumps. The zeotropic mixture has the potential to meet all the above demands at appropriate operating parameters, although specific feasible mixtures are still under investigation. In this work, a novel mixture of carbon dioxide and trans-1,1,1,4,4,4-hexafluoro-2-butene is proposed, with the heating performance being parametrically optimized based on a genetic algorithm. Energy analysis indicates a coefficient of performance improvement of up to 15.7 %, and thus an improvement in heating seasonal performance factor of more than 13.5 % for different cities, compared with traditional configurations. Exergy analysis shows that the low irreversibility of throttling is the main contributing factor to the improvement in energy efficiency. Meanwhile, economic and environmental analyses reveal a payback period of less than 7.5 years and an annual cost reduction of up to 14.5 %, as well as a carbon dioxide emission reduction of over 15.7 %. The sensitivity of operating parameters is analyzed, and other advantages of this concept are discussed as well. The results indicate a safe, efficient, environmentally friendly, and cost-effective air-source heat pump. This study contributes to: 1) providing an energy-efficient and environmentally friendly alternative refrigerant for heat pumps; and 2) promoting the sustainable development of low-carbon energy transformation technology.

Enhanced thermally integrated Carnot battery using low-GWP working fluid pair: Multi-aspect analysis and multi-scale optimization

Thermally integrated Carnot battery (TICB) emerges as a promising technology for long-duration energy storage. This study aims to improve its multi-dimensional performance from the optimization design level, thereby promoting its competitiveness. Firstly, a refined system architecture is developed, integrating subsystem layout modification and advanced thermal integration mode. Sixteen potential working fluid pairs are formed by screening low-GWP refrigerants as drop-in substitutes for R245fa. Then, a comprehensive evaluation framework is established to characterize this technology from energy, exergy, and economic perspectives, and a collaborative optimization method is introduced to facilitate integrated optimization. Finally, a whole cycle cumulative exergy analysis is conducted to explore directions for further improvement. Results indicate that, compared to the basic architecture, the round-trip efficiency (RTE) of the proposed system is elevated by over 30%. The use of different alternative refrigerants in the charging and discharging cycles makes the TICB not only sustainable but also more efficient. The thermodynamic dilemma of determining the heat pump evaporation temperature disappears with a closed-type heat source. To maximize overall thermo-economics, sufficient heat pump subcooling and evaporator internal superheat are necessary, and the ideal storage temperature span and pinch point temperature difference of heat exchangers must be identified. The collaborative optimization displays that the first-rank working fluid pair is R1234ze(Z)-R1224yd(Z), with an RTE of 85.2%, a volumetric energy density of 3.10 kWh/m3, and a levelized cost of storage of 0.303 $/kWh, respectively. Furthermore, the RTE is highly sensitive to the insulation quality of storage tanks. A mere 2.5% performance degradation can lead to a 10% points decline in RTE. Internal exergy destruction is primarily caused by poor heat transfer matching, while external exergy loss mainly results from underutilized heat sources during non-charging periods. Therefore, we recommend the district heating network as the target heat source for the dual-period TICB. These achievements offer a valuable reference for the research and development of efficient, affordable, and sustainable TICB.

Thermal characteristics of nanofluid ice slurry flowing through a spiral tube: A computational study

Nanofluid ice slurry (NICS) has recently attracted significant attention in the field of thermal engineering as an alternative refrigerant, offering a cost-effective, stable, and environmentally friendly cold storage solution. To maximize its potential, a thorough understanding of its heat transfer characteristics is crucial. Unfortunately, this information is not available for spiral tubes which are commonly used in thermal systems due to their superior heat transfer performance. This may hinder further development and implementation of this technology. Hence, the present investigation aims to analyze the flow characteristics and heat transfer mechanisms of a graphene oxide hybrid NICS within a spiral tube employing a computational fluid dynamics (CFD) methodology. More specifically, an interphase heat and mass transfer model, derived from the Euler–Euler model, is formulated to accurately represent the phase transition phenomena occurring within the nanofluid. The results indicate that the spiral tube structure enhances ice crystal accumulation inside the tube, leading to lower outlet temperatures and improved heat transfer without causing ice blockage. The NICS shows a 3% higher pressure drop compared to pure water ice slurry. Increased nanoparticle concentrations enhance thermal conductivity, benefiting heat transfer, but also raise viscosity, resulting in greater internal friction. A Nusselt correlation based on Prandtl and Dean numbers is formulated to aid future studies and the design of NICS systems. When the Reynolds number increases from 3600 to 6600, the Nusselt number rises by approximately 21% for pure water ice slurry and 22% for nanofluid ice slurry.

ANALYSIS OF SUITABLE METHODOLOGIES FOR COMPRESSOR MASS FLOW RATE CORRECTION TO OTHER SUPERHEAT LEVELS AND REFRIGERANTS

This paper investigates the impact of suction conditions and refrigerant on scroll compressor mass flow rate by using calorimeter tests from AHRI-11 and AHRI-21 reports, published by AHRI's Low-GWP Alternative Refrigerants Evaluation program. Two Copeland scroll compressors (20 and 51 cm3) have been analyzed including different suction conditions (SH = 11K, SH = 22K, Ti = 18ºC) and several refrigerants (R134a, R32, R410A, R404A, etc.). Previous studies have explored response surfaces for energy consumption and mass flow rate variables. This study aims to expand the analysis by identifying the optimal approach to extrapolate mass flow rate from specific suction conditions to others SH or suction temperature levels and refrigerants. The current compressor characterization standard relies on the 1981 Dabiri correlation to correct compressor mass flow rate with suction conditions. Thus, this study aims to assess the adequacy of this correction and explore alternative correction methods for improved results.

Refrigerant Selection in Air Conditioning Systems Considering Thermodynamic, Environmental, and Economic Performance Using the BHARAT-II Multi-Attribute Decision-Making Method

A simple and effective multi-attribute decision-making method, named as "Best Holistic Adaptable Ranking of Attributes Technique (BHARAT)-II”, to choose the best refrigerant for air conditioning systems is presented. The thermodynamic properties of the refrigerants, and their environmental, and economic performances are also considered for the selection. Two case studies are provided to demonstrate the proposed multi-attribute decision-making method. The first case study addresses the problem of selecting the best refrigerant for residential split air conditioners out of 15 alternative refrigerants considering 12 selection attributes; the second case study addresses the problem of selecting the best refrigerant for automobile air conditioning systems by considering 14 alternative refrigerants and 13 selection attributes. The results of the proposed decision-making method are compared with those of other well-known multi-attribute decision-making methods such as EDAS, TOPSIS, and MOORA. The proposed method is shown to be simple to implement, providing a logical way for allocating weights to the selection attributes and is useful to solve the best alternative refrigerant selection problems of the residential as well as industrial refrigeration and air conditioning.

Evaluation of energy performance and environmental benefits for transcritical CO2 thermal system in high-speed trains

The conventional air conditioning system used in high-speed railways has limitations in heating performance and environmental impact, necessitating the exploration of alternative refrigerants. The transcritical CO2 system has gained popularity due to its exceptional heating efficiency and environmental benefits. This study aims to evaluate the energy and environmental potentials for transcritical CO2 systems in high-speed trains based on four-vertical-and-four-horizontal railway lines within different climatic regions of China. A high-fidelity transcritical CO2 system model was first developed and validated through experiments. Then, a comprehensive energy and environmental evaluation method was proposed and applied to the four-vertical-and-four-horizontal railway lines. The results indicated that the transcritical CO2 system had a superior heating performance and competitive cooling performance based on daily and annual operations. Furthermore, the transcritical CO2 system exhibited significant environmental advantages with lower total life cycle climate performance for all lines, with an average emissions reduction ratio of 17.6% and a maximum emissions reduction ratio of 26.98%. These findings highlight the competitive energy performance and outstanding environmental benefits offered by transcritical CO2 systems as promising alternatives to air conditioning systems in railway transportation.

Research on the lubricating oil leakage characteristics in the vapor compression heat pump system under refrigerant leaking

Refrigerant leakage is a situation that often occurs in refrigeration equipment such as heat pumps. However, certain alternative refrigerants, while exhibiting superior environmental performance, possess varying levels of flammability. The leakage of flammable refrigerants into confined spaces can pose a significant risk of explosion. The amount of lubricant in the leaking refrigerant will undoubtedly affect the flammability characteristics of the refrigerant. In this paper, the content of PVE32 oil in the leaking refrigerant during the operation of a heat pump was investigated. The results showed that, under the five leakage rate scenarios set up in the experiment, the oil concentration was highest when the leakage occurred at the condenser inlet and lowest when the leakage was at the evaporator outlet. During the leakage process of the experiment, as the mass flow rate of the leakage increased, the oil content in the early stage of the leakage increased, but the oil content in the late stage of the leakage decreased. The reasons for the change in oil content were analyzed by the oil circulation rate and the degree of phase separation. The decrease of the oil circulation rate and the change of the degree of phase separation were the key factors affecting the magnitude of the oil content as the leakage proceeded. The results of the study reveal the leakage characteristics of lubricating oil with refrigerant leakage.

Optimizing air conditioning efficiency: Utilizing nano-oxides ZnO, CuO, and TiO2 with traditional and alternative refrigerants in medium temperature range cooling systems

Optimizing air conditioning efficiency: Utilizing nano-oxides ZnO, CuO, and TiO2 with traditional and alternative refrigerants in medium temperature range cooling systems

Thermodynamic optimization of heat exchanger circuitry via genetic programming

In this study, an evolutionary thermodynamic technique was developed for the optimization of heat exchanger circuitry. The proposed technique is capable of handling the unrestrained implementation of genetic operators while ensuring circuitry feasibility and basic manufacturability. The optimization tool was used to clarify the optimal heat transfer features in relation to the characteristics of the refrigerant and to provide a thermodynamic interpretation of the optimization results to extract general design guidelines. Evaporator circuitry optimization was conducted under given cooling capacity, superheating degree, and boundary conditions representative of air-conditioning applications. The consistency between the minimum entropy generation and the maximum coefficient of performance (COP) was demonstrated under these settings. Accordingly, heat exchanger configurations that take maximum advantage of the thermodynamic benefits of each refrigerant are proposed by optimizing the distribution of friction and heat transfer irreversibility. Consequently, the evaporator outlet pressure increases, thus lowering the compression ratio and maximizing the COP. The developed optimization method maximizes the benefits of low-GWP alternative refrigerants and shows that zeotropic mixtures may exhibit performance analogous to that of R32 and higher than that of R410A by approaching a Lorenz cycle operation.

Literature Review on Experimental Analysis of Domestic Refrigerator

Abstract: This literature review paper delves into the experimental analysis of the performance of domestic refrigerators, a cornerstone of modern household appliances. The review synthesizes a broad spectrum of studies that examine the efficiency, energy consumption, cooling capacity, and overall performance of various domestic refrigerator models. Key focus areas include the impact of different refrigerants, advancements in compressor technology, insulation materials, and the role of smart technologies in enhancing refrigerator performance. The review highlights experimental methodologies employed to assess refrigerator performance, such as standardized testing protocols, real-world usage simulations, and advanced diagnostic techniques. It also discusses the influence of external factors like ambient temperature, door opening frequency, and load variability on refrigerator efficiency. Comparative analyses within the literature reveal trends in energy efficiency improvements, driven by regulatory standards and consumer demand for environmentally friendly appliances. The integration of alternative refrigerants, such as R600a (isobutane), is examined for its environmental benefits and performance implications. The paper concludes by identifying gaps in current research and suggesting directions for future experimental studies. Emphasis is placed on the need for continued innovation in refrigeration technologies to meet growing energy efficiency and environmental sustainability requirements. Overall, this literature review provides a comprehensive overview of the experimental evaluation techniques and findings related to domestic refrigerator performance, offering insights that can guide future research and development in this vital field.

Experimental and Theoretical Assessment of Inverter-Operated Split Air Conditioner with Low GWP Alternative Refrigerants

This article presents experimental evaluation and comparative analysis of low GWP alternative refrigerants, namely HC-290 (propane), HC-1270 (propylene), HC/HC-1270 blend, and HFC-32 (difluoro methane) as drop-in replacements for HCFC-22 (Chloro difluoro methane) in a typical 1.5 TR capacity inverter operated split type air conditioner (SAC). The experimental setup consisted of retrofitting an original HCFC-22 test unit following the soft optimization of the SAC system for each alternative refrigerant, followed by testing under controlled operating conditions as per the IS 1391, Part-1 standard at the half capacity and the rated capacity of inverter SAC. The results obtained were compared against the baseline HCFC-22 test unit. The optimized SAC gave EERIS (Indian Seasonal Energy Efficiency Ratio) of 4.63 for HC-290, 4.71 for HC-1270 and 4.87 for HC-290/HC-1270 blend, respectively increased by 8.94 %, 10.82 % and 14.58 % compared to HCFC-22. HFC-32 delivered the maximum cooling capacity of 6.78 kW, 3.67 % higher than baseline unit at the rated capacity. HC-290/HC-1270 blend exhibited the lowest power consumption and discharge temperature amongst all the refrigerants considered. The charge of flammable refrigerants has been optimized below LFL satisfying EN378 standard for the safety of inverter SAC in domestic applications.

R455A Refrigerant as a Prospective Working Fluid in Refrigeration Systems for Gastronomy Furnishings

The general development of technology and universal access means that gastronomy furnishings can be found in every corner of the world. Therefore, it is important to develop these devices and the machines that constitute them. We are talking about refrigeration systems located inside gastronomy furnishings. The R404A refrigerant, popular in recent years, is being withdrawn from use due to its harmful impact on the environment. Modern synthetic refrigerants or natural refrigerants can be used as alternative substances. In modern solutions, it is expected that devices and all cooperating elements have the lowest possible harmful impact on the environment and the user while, at the same time, having the highest possible energy efficiency. First, tests were carried out with the R404A refrigerant. Then, the working medium was replaced without changing any element of the refrigeration system with the modern R455A refrigerant. The system was tested in terms of the operating parameters achieved and in terms of electricity consumption. It was found that there is an alternative R455A refrigerant operating in the refrigeration system of catering furnishings, which provides the system with an average of 34% better energy efficiency than the reference refrigerant R404A. It was also found that the time needed to achieve the set working conditions decreased. An alternative refrigerant allows a refrigeration system to be built based on components available on the market or one that can be used as a direct replacement for the old refrigerant.

Assessment of using different ozone-friendly R22 alternative refrigerants in residential air conditioners in a high-ambient temperature country

The performance of a vapor compression refrigeration system (VCRS)-based residential air conditioner operating in a high-ambient temperature (HAT) country was investigated using six zero-ODP (ozone depletion potential) refrigerants as replacements to R22. The non-flammable alternative refrigerants considered in the present research were R134a, R404A, R407C, R410A, R448A, and R507A. Using the basic conservation laws, the VCRS was modeled during steady-state operation and solved using engineering equation solver (EES) software. Coefficient of performance (COP), pressures and temperatures at compressor suction and discharge, Global Warming Potential (GWP), critical pressure and temperature, compressor pressure ratio, volumetric cooling capacity (VCC) specific cooling capacity (SCC), and refrigeration effect were utilized as assessment criteria for the alternative refrigerants considered. From these refrigerants, the highest values of suction pressure, discharge temperature, and condenser pressure were attained by R410A. In addition, the discharge temperatures for all refrigerants, except R134a, were all higher than their corresponding critical values, causing a quicker drop in the VCRS’s performance. As an alternative refrigerant, R407C showed the highest SCC of 141.0 kJ/kg followed directly by 139.2 and 138.0 kJ/kg for R410A and R448A, respectively. A reverse trend was found for VCC with respective values of 4722 and 3775 kJ/m3 for R410A and R448A. Lower volume flow rates and smaller-sized compressors are expected for higher VCC refrigerants. The same trend was found for the compressor’s specific work input and condenser’s specific heat transfer with values of (51.14, 46.82, and 45.38 kJ/kg) and (190.3, 187.8, and 183.4 kJ/kg) for R410A, R407C, and R448A, respectively. For applications in HAT countries, larger condenser’s specific heat transfer makes the refrigerant more applicable. Conversely, with respect to COP, refrigerant R134a with a value of 3.075 was the superior alternative followed by R448A and R407C with respective COPs of 3.042 and 3.011. Based on the overall assessment in terms of environmental obligation, COP, compressor input power, refrigerant flow rate required, and all the evaluations made in this research, refrigerant R448A was recommended as the most appropriate substitute to R22 which can effectively be used in residential air conditioners in a HAT country.