The Experts below are selected from a list of 12270 Experts worldwide ranked by ideXlab platform
Vaclav Dvorak - One of the best experts on this subject based on the ideXlab platform.
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hfo1234ze e as an alternative refrigerant for ejector cooling technology
Energies, 2019Co-Authors: Van Vu Nguyen, Szabolcs Varga, Vaclav DvorakAbstract:The paper presented a mathematical assessment of selected Refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known Refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon Refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected Refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance.
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hfo1234ze e as an alternative refrigerant for ejector cooling technology
Energies, 2019Co-Authors: Van Vu Nguyen, Szabolcs Varga, Vaclav DvorakAbstract:The paper presented a mathematical assessment of selected Refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known Refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon Refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected Refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance.
Weihua Zeng - One of the best experts on this subject based on the ideXlab platform.
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refrigerant alternative and optimization under the constraint of the greenhouse gas emissions reduction target
Journal of Cleaner Production, 2021Co-Authors: Huihui Wang, Linjia Zhao, Ruoxin Cao, Weihua ZengAbstract:Abstract Fluorinated gases are considered greenhouse gases and have a global warming effect up to 22,800 times greater than that of carbon dioxide. Fluorinated gases are widely used as room air conditioner Refrigerants. In view of the current lack of well-equipped refrigerant replacement technology and research on comprehensive and systematic refrigerant alternative schemes, we propose a decision-making method system for optimizing room air conditioner refrigerant alternative schemes suitable for meeting future greenhouse gases emissions reduction target constraints by integrating the life cycle assessment method, the system dynamics method and the multi-objective programming method. In accordance with the requirements of the Montreal Protocol and other relevant fluorine-containing substance elimination plans, four scenarios for refrigerant alternative schemes were designed, which include Business as usual scenario, Convention Scenario, Design Scenario and Ideal Scenario, respectively. The Convention Scenario is based on the refrigerant phase-out plan stipulated by international conventions in China; the Ideal Scenario is based on the use of Refrigerants with minimal environmental impact within the range of available predictable technologies; and the Design Scenario is designed according to the degree of strictness between the Convention Scenario and the Ideal Scenario and used to propose more reasonable and feasible refrigerant use planning schemes. The results show that the ozone depletion ability of Refrigerants will be eliminated with the phase-out of hydrochlorofluorocarbon refrigerant HCFC-22. The total cost of refrigerant substitution work under different alternative scenarios will cost a total of $1.378 billion to $1.672 billion, which is worthwhile considering the considerable environmental benefits. The refrigerant dosage scheme under design scenario II, which is 50% faster than the conventional phase-out scheme, is the optimal scheme for future refrigerant replacement phase-out in the room air conditioner industry. Under this scenario, the total economic cost is $1.672 billion; additionally, compared with those under the business as usual scenario, the greenhouse effect intensity will decrease by 78.2%, the safety risk will decrease by 6.8%, the energy consumption will decrease by 60.4% and the ozone depletion ability will decrease by 99.8%.
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reduction of potential greenhouse gas emissions of room air conditioner Refrigerants a life cycle carbon footprint analysis
Journal of Cleaner Production, 2015Co-Authors: Linjia Zhao, Weihua Zeng, Zengwei YuanAbstract:Abstract Fluorinated gases (F-gases) are considered to be greenhouse gases (GHG) and are widely used as room air conditioner (RAC) Refrigerants. This study was initiated to determine the potential to reduce the GHG emission of the RAC Refrigerants by calculating their life cycle carbon footprints (CFPs). The life cycle of a refrigerant includes the processes of production, filling of RACs, service, disposal, and energy consumption. The refrigerant functional unit was assumed to produce 1 kW of cooling capacity. The assumed calculation conditions included an RAC service life of 10 years and a unit usage use of 2 h per day, 100 days per year. Specifically, the GHG emission reduction potential of Refrigerants was further analyzed based on 15%, 30% and 50% refrigerant recycle rates scenarios. RAC Refrigerants were divided into three types: high global warming potential (GWP), middle GWP and low GWP. Analysis of the results indicated that the life cycle CFPs of high GWP Refrigerants were larger than those of the middle and low GWP Refrigerants. Service and disposal processes contributed most to RAC Refrigerants' life cycle CFPs. There are two ways to reduce the GHG emission of RAC Refrigerants. One approach is to avoid direct GHG emissions during the disposal process. When the refrigerant recycle rate was improved from 5% to 15%, 30%, and 50%, the reduction of GHG emission of the Refrigerants increased by 5%, 12%, and 20%, respectively. The second method is to substitute middle and low GWP Refrigerants for high GWP Refrigerants. This method can lead to a GHG emission reduction of at least 45.57%.
Linjia Zhao - One of the best experts on this subject based on the ideXlab platform.
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refrigerant alternative and optimization under the constraint of the greenhouse gas emissions reduction target
Journal of Cleaner Production, 2021Co-Authors: Huihui Wang, Linjia Zhao, Ruoxin Cao, Weihua ZengAbstract:Abstract Fluorinated gases are considered greenhouse gases and have a global warming effect up to 22,800 times greater than that of carbon dioxide. Fluorinated gases are widely used as room air conditioner Refrigerants. In view of the current lack of well-equipped refrigerant replacement technology and research on comprehensive and systematic refrigerant alternative schemes, we propose a decision-making method system for optimizing room air conditioner refrigerant alternative schemes suitable for meeting future greenhouse gases emissions reduction target constraints by integrating the life cycle assessment method, the system dynamics method and the multi-objective programming method. In accordance with the requirements of the Montreal Protocol and other relevant fluorine-containing substance elimination plans, four scenarios for refrigerant alternative schemes were designed, which include Business as usual scenario, Convention Scenario, Design Scenario and Ideal Scenario, respectively. The Convention Scenario is based on the refrigerant phase-out plan stipulated by international conventions in China; the Ideal Scenario is based on the use of Refrigerants with minimal environmental impact within the range of available predictable technologies; and the Design Scenario is designed according to the degree of strictness between the Convention Scenario and the Ideal Scenario and used to propose more reasonable and feasible refrigerant use planning schemes. The results show that the ozone depletion ability of Refrigerants will be eliminated with the phase-out of hydrochlorofluorocarbon refrigerant HCFC-22. The total cost of refrigerant substitution work under different alternative scenarios will cost a total of $1.378 billion to $1.672 billion, which is worthwhile considering the considerable environmental benefits. The refrigerant dosage scheme under design scenario II, which is 50% faster than the conventional phase-out scheme, is the optimal scheme for future refrigerant replacement phase-out in the room air conditioner industry. Under this scenario, the total economic cost is $1.672 billion; additionally, compared with those under the business as usual scenario, the greenhouse effect intensity will decrease by 78.2%, the safety risk will decrease by 6.8%, the energy consumption will decrease by 60.4% and the ozone depletion ability will decrease by 99.8%.
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reduction of potential greenhouse gas emissions of room air conditioner Refrigerants a life cycle carbon footprint analysis
Journal of Cleaner Production, 2015Co-Authors: Linjia Zhao, Weihua Zeng, Zengwei YuanAbstract:Abstract Fluorinated gases (F-gases) are considered to be greenhouse gases (GHG) and are widely used as room air conditioner (RAC) Refrigerants. This study was initiated to determine the potential to reduce the GHG emission of the RAC Refrigerants by calculating their life cycle carbon footprints (CFPs). The life cycle of a refrigerant includes the processes of production, filling of RACs, service, disposal, and energy consumption. The refrigerant functional unit was assumed to produce 1 kW of cooling capacity. The assumed calculation conditions included an RAC service life of 10 years and a unit usage use of 2 h per day, 100 days per year. Specifically, the GHG emission reduction potential of Refrigerants was further analyzed based on 15%, 30% and 50% refrigerant recycle rates scenarios. RAC Refrigerants were divided into three types: high global warming potential (GWP), middle GWP and low GWP. Analysis of the results indicated that the life cycle CFPs of high GWP Refrigerants were larger than those of the middle and low GWP Refrigerants. Service and disposal processes contributed most to RAC Refrigerants' life cycle CFPs. There are two ways to reduce the GHG emission of RAC Refrigerants. One approach is to avoid direct GHG emissions during the disposal process. When the refrigerant recycle rate was improved from 5% to 15%, 30%, and 50%, the reduction of GHG emission of the Refrigerants increased by 5%, 12%, and 20%, respectively. The second method is to substitute middle and low GWP Refrigerants for high GWP Refrigerants. This method can lead to a GHG emission reduction of at least 45.57%.
Van Vu Nguyen - One of the best experts on this subject based on the ideXlab platform.
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hfo1234ze e as an alternative refrigerant for ejector cooling technology
Energies, 2019Co-Authors: Van Vu Nguyen, Szabolcs Varga, Vaclav DvorakAbstract:The paper presented a mathematical assessment of selected Refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known Refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon Refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected Refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance.
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hfo1234ze e as an alternative refrigerant for ejector cooling technology
Energies, 2019Co-Authors: Van Vu Nguyen, Szabolcs Varga, Vaclav DvorakAbstract:The paper presented a mathematical assessment of selected Refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known Refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon Refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected Refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance.
Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.
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A performance comparison of vapour-compression refrigeration system using various alternative Refrigerants
International Communications in Heat and Mass Transfer, 2010Co-Authors: Ahmet Selim Dalkılıç, Somchai WongwisesAbstract:Abstract A theoretical performance study on a traditional vapour-compression refrigeration system with refrigerant mixtures based on HFC134a, HFC152a, HFC32, HC290, HC1270, HC600, and HC600a was done for various ratios and their results are compared with CFC12, CFC22, and HFC134a as possible alternative replacements. In spite of the HC Refrigerants' highly flammable characteristics, they are used in many applications, with attention being paid to the safety of the leakage from the system, as other Refrigerants in recent years are not related with any effect on the depletion of the ozone layer and increase in global warming. Theoretical results showed that all of the alternative Refrigerants investigated in the analysis have a slightly lower performance coefficient (COP) than CFC12, CFC22, and HFC134a for the condensation temperature of 50 °C and evaporating temperatures ranging between − 30 °C and 10 °C. Refrigerant blends of HC290/HC600a (40/60 by wt.%) instead of CFC12 and HC290/HC1270 (20/80 by wt.%) instead of CFC22 are found to be replacement Refrigerants among other alternatives in this paper as a result of the analysis. The effects of the main parameters of performance analysis such as refrigerant type, degree of subcooling, and superheating on the refrigerating effect, coefficient of performance and volumetric refrigeration capacity are also investigated for various evaporating temperatures.
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flow characteristics of pure Refrigerants and refrigerant mixtures in adiabatic capillary tubes
Applied Thermal Engineering, 2001Co-Authors: Somchai Wongwises, Worachet PirompakAbstract:Abstract This paper provides the results of simulations using an adiabatic capillary tube model which is developed to study the flow characteristics in adiabatic capillary tubes used as a refrigerant control device in refrigerating systems. The developed model can be considered as an effective tool of capillary tubes' design and optimization for systems using newer alternative Refrigerants. The model is validated by comparing with the experimental data of Li et al. and Mikol for R12 and Melo et al. for R134a. In particular, it has been possible to compare various pairs of Refrigerants. It is found that the conventional Refrigerants consistently give longer capillary lengths than the alternative Refrigerants. For all pairs, the conventional refrigerant consistently give lower pressure drops for both single-phase and two-phase flow which resulted in longer tube lengths. In addition, an example of capillary tube selection chart developed from the present numerical simulation is shown. The chart can be practically used to select the capillary tube size from the flow rate and flow condition or to determine mass flow rate directly from a given capillary tube size and flow condition. The results of this study are of technological importance for the efficient design when systems are assigned to utilize various alternative Refrigerants.
