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Heat pump systems are often considered as one of the major contributors to environmental problems due to the usage of chlorofluoro, hydrochlorofluoro, and hydrofluoro carbon-based refrigerants. Earlier versions of refrigerants used to have high ODP as well as GWP. However, next generation refrigerants that are environmentally benign with excellent...
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... refrigerant is the heat transfer fluid in refrigeration and air-conditioning systems. It absorbs heat from one area, such as space which needs to be cooled, and reject heat into outdoors, usually by evaporation and condensation, respectively 16) . Conventional vapor compression system is used to provide thermal comfort. Fig. 1 17) shows the schematic diagram of a typical vapor compression cycle comprises the following four essential elements: an evaporator, where the refrigerant evaporates by taking heat from the external environment. A mechanical compressor, which sucks the evaporated vapors to compress and expel it at a higher pressure and temperature. The ...
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... According to a study by Gschrey et al. 11) , contribution of F-gases to global warming will increase from 1.3% (2004) to 7.9% (2050) of total CO2 emissions in the business-as-usual scenario. HFC emissions are mainly associated with a lack of proper refrigerant management practices 12) . Given the growing global demand for cooling due to global warming and the increasing share of cooling in GHG emissions, refrigerant management covering leakage prevention is considered one of the most impactful actions for climate change mitigation in the future 13) . ...
... However, its use in domestic heating has been dramatically reduced due to its high ozone depletion potential (ODP), equal to 0.055, and its high GWP index, equal to 1,960. 42,43 R134a has been another widely used fluid that does not damage the ozone layer and has a lower GWP index than R22 (1,530; Figure 4B), but it is also being phased out of low-temperature heating applications. It is associated with an average COP of 2.5, which is competitive with other options, but it requires larger components and the estimated LCOH is higher than its successors. ...
... Selecting the optimal refrigerant pair for CRS has been a subject of intensive research in recent years, and various combinations have been studied (Llopis et al., 2019;Thu et al., 2021). When exploring suitable refrigerant alternatives, certain constraints must be considered, including the performance of the refrigeration system (COP sys , η II ), environmental concerns (GWP, ODP), and operational safety (flammability, high pressures) (Pal et al., 2018;Perera et al., 2021;Sanz-Kock et al., 2014). ...
This study presents a comparative energy, exergy, and life cycle climate performance (LCCP) analysis of various refrigerants in a cascade refrigeration system (CRS). The refrigerants analyzed in the low-temperature cycle (LTC) include R-23, R-116, R-41, R-170, R-1150, and R-1132a whereas high-temperature cycle (HTC) utilizes R- 404A, R-455A, R-454C, R-459B, R-161, R-290, R-1270, and R-1234yf. For the first time for CRS, LCCP analysis is conducted and fourth generation low GWP and less flammable prospective refrigerants R-1132a, R-455A, R- 454C, R-459B are analyzed. The study aims to find a refrigerant pair that outperforms R-23/R-404A in terms of thermodynamic efficiency while also considering environmental impact and safety considerations. Among the 48 refrigerant groups analyzed, the study reveals that R-170/R-161 and R-41/R-161 demonstrate superior performance in terms of thermodynamic efficiency and environmental impact assessment whereas the largest exergy destruction components are HTC/LTC compressors. However, if flammability is a major concern, the recommended refrigerant pair is R-1132a/R-1234yf, as it is a suitable alternative in terms of safety considerations while still maintaining favorable thermodynamic and environmental performance.
... It is primarily driven by the increase in greenhouse gases resulting from global warming and contributing to the depletion of the ozone layer. The concentration of these gases in the troposphere is rising, largely due to human-made activities such as electricity production, industrialization, and transportation 1) . Recent assessments from the International Energy Agency revealed that approximately 25% of global CO2 emissions could be attributed to the transportation industry 2,3) . ...
... R-32 is receiving much attention and it is expected to be a next-generation refrigerant [46,47] given its potential to reduce electricity demand, easy recyclability and one-third lower GWP compared to R-410a. If all R-410a were converted to R-32, the impact of global warming from HFCs in 2030 is estimated to be reduced by the GWP 100 CO 2 -eq of approximately 800 million tons (19%) compared to the continued use of R-410a [48]. Thus, several major manufacturers [49,50] are at the forefront of implementing its use. ...
This paper examines the metrics used to account for the contribution to global warming from fluorinated gases (f-gases) mainly used as refrigerants for cooling. F-gases are key to climate mitigation discussion as they a) are critical to delivering the surging demand for air conditioners which is expected to triple by 2050, b) have strong Global Warming Potential (GWP) as high as 12,000 kgCO2-eq (for e.g., HFC-23) and c) are targeted by international policy agreements such as the Montreal Protocol and Kigali Amendment. F-gases exacerbate atmospheric warming when leaked from cooling equipment, or during other phases of their life cycle. Thus far, the way these gases impact global warming is mostly reported based on their CO2-equivalent emissions with a time horizon of 100 years. However, the problem is that f-gases have significantly different lifespans and the GWP100 does not account for these variations. The debate on metrics to account for warming of other short-lived climate pollutants (SLCP), such as methane is already ongoing. Here, we provide the first step to open such debate for short-lived f-gases. We address this, first, with a critical review of the available metrics for carbon foot-printing of f-gases and present a gap analysis between the existing carbon foot printing metrics and the need to better understand warming from f-gases. Second, we use an atmospheric model to illustrate how the incumbent metric (CO2-equivalent calculated using GWP100), misrepresent the warming of an exemplary f-gas refrigerant (HFC-134a). The model outputs novel profiles of atmospheric concentration, radiative forcing, and temperature, in three scenarios. Scenario A models the response to a positive step change in emissions of the HFC, while Scenario B is the inverse. Scenario C models a reduction of 85% by 2036 of emissions according to targets for high-emitting countries set in the Kigali Amendment. The modelling results evidence that the commonly used CO2-equivalent with its GWP100 does not represent the atmospheric responses, and particularly the warming of the exemplary short-lived HFC. Through the literature review, however, we identify many other metrics available that could be applied for f-gases, and particularly GWP* is recommended to examine in future works. In summary, the paper offers insights into which metrics can best help to identify the effects of f-gases in terms of reducing global warming in a rapid timeframe, and how CO2-equivalents should not be used as proxy for atmospheric warming in policy discussions.
... Climate change and the ozone layer depletion are the most direct threats to humanity 1) 2) . Increasing levels of greenhouse gases in the troposphere have been caused by human activities such as burning forests, clearing agricultural lands, and using fossil fuels excessively 3) . On a national scale, most studies estimate that 35% to 49% of the energy used for comfort conditions in residential and industrial buildings goes towards providing comfort 4) 5) 6) . ...
Because of the complexity involved, most researchers avoid studying the entropy generation due to both convection and radiation. In this study, the heat transfers from the horizontal heated cylinder by natural convection and radiation and the entropy generation is the case study and the ability to combine of these two heat transfer methods depending on the thermodynamic principles. Three heating horizontal cylinders were used during this study. The results indicated that the natural convection is effective parameter to produce the entropy generation when the ratio of Ra/Ra, opt lower than 1 and the Ns increased slightly to 3 at Ra/Ra, opt=0.001, but when the radiation is the effective parameter to produce the entropy generation that is done when Ra/Ra, opt higher than 1 and the Ns increases to 200 at Ra/Ra, opt=1000.
... Recognizing the importance of environmental commitments as well as the need to comply with international rules and regulations, the relevant industry and research community began looking for low-GWP refrigerants around 2011. We have a few low-GWP refrigerants in the market, but they are not suitable for replacing the existing halogenated refrigerants [41,42]. This study was concentrated on ultra-low and low-GWP refrigerants providing system performance comparable to or better than that of the existing refrigerants in residential air conditioning. ...
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
... The vapor refrigerant condenses in the condenser by transferring heat to the outdoor environment. Finally, through the expansion valve, the liquid refrigerant returns to the evaporator having a lower pressure for the cycle's repetition [10]. ...
... Considering the leakage of these systems, equivalent CO 2 emission value has been calculated and analyzed based on the leakage rate and initial charge number of different refrigerants. Different air conditioning and refrigeration systems have been included in this research in terms of their types and sizes [10]. ...
... Schematic diagrams of the Vapor Compression Refrigeration System[10,11]. ...
The Vapor Compression Refrigeration System (VCRS) is one of the most critical systems in buildings typically used in Heating, Ventilation, and Air Conditioning (HVAC) systems in residential and industrial sections. Therefore, identifying their faults and evaluating their reliability are essential to ensure the required operations and performance in these systems. Various components and subsystems are included in the VCRS, which need to be analyzed for system reliability. This research’s objective is conducting a comprehensive system reliability analysis on the VCRS by focusing on fault identification and determining the fault impacts on these systems. A typical VCRS in an office building is selected for this research regarding this objective. The corresponding reliability data, including the probability distributions and parameters, are collected from references to perform the reliability evaluation on the components and subsystems of the VCRS. Then the optimum distribution parameters have been obtained in the next step as the main findings. Additionally, by applying optimization techniques, efforts have been taken to maximize the system’s reliability. Finally, a comparison between the primary and the optimized systems (with new distribution parameters) has been performed over their lifetime to illustrate the system’s improvement percentage.
... Bangladesh is vulnerable to climate change as a consequence of global warming 1) . This country has also been experiencing environmental degradation for the last decades. ...
... The research revealed that extremely excellent results may be achieved with the R32/R1123 combination, which can be used as an alternative to R410A [29]. Another study emphasizes the criteria for selecting environmentally friendly next-generation refrigerants that can replace the existing refrigerants used in heat pumps [21]. Research is being conducted on the flammability of refrigerants such as R600a and R290, which are known to be natural and environmentally friendly. ...
It is known that the performance of vapor compression cooling systems can be increased thanks to the ejector. In the literature, there are many studies on the subject, in which mathematical models of ejector-expansion cooling systems are developed. However, the refrigerant velocities at the mixing section inlet for the secondary flow (suction stream) and diffuser outlet were neglected in these studies. In the mathematical model used in this study, the velocities in both sections are considered and the system performance is calculated. The performance assessment of an ejector-expansion refrigeration system was realized in the case of using the R600a/R290 refrigerant mixture as a working fluid. Thus, the effect of zeotropic refrigerant mixtures on the system performance is also investigated, considering the refrigerant velocities at the mixing section inlet and diffuser outlet. According to the obtained results, it has been found that the cooling performance of the system that uses R600a/R290 mixture as a refrigerant is 5.8%-7% higher when the velocities at the mixing section inlet and diffuser outlet are considered compared to the neglected one. The exergy efficiency is also calculated to be around 4.6% lower when the ejector mixing section inlet and diffuser outlet velocities are neglected.
