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M Fatouh - One of the best experts on this subject based on the ideXlab platform.
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energy and exergy analysis of a household refrigerator using a ternary hydrocarbon mixture in tropical environment effects of refrigerant charge and capillary length
Applied Thermal Engineering, 2018Co-Authors: M Fatouh, Hosny Z AbouziyanAbstract:Abstract This paper examines the energy quality of a household refrigerator working with a ternary hydrocarbon mixture (THM) of 60% propane, 26.6% isobutane, and 13.4% n-butane. Exergy and energy analyses are based on experimental continuous tests of a single evaporator refrigerator for different charges (30–70 g) and capillary tube lengths (4–6 m). The tests are conducted in a climatic chamber at 43 °C and 50% relative humidity. Analysis of experimental data indicated that both THM charge and capillary tube length have substantial effects on the energy and exergy characteristics of Refrigerators. The results indicated that exergy efficiency increases as subcooling degree or refrigerant charge increases and as capillary tube length, pressure ratio, and superheating degree decrease. Also, constant speed compressor and capillary tube are responsible for over 88% of refrigerator exergy loss. Refrigerator, using 70 g THM charge and 4 m capillary tube, affords the largest COP, exergy efficiency and cooling capacity and the lowest pressure ratio. Also, it secures cycle stabilization as it achieves the largest subcooling degree and lowest superheating degree. This household refrigerator achieves better characteristics than those obtained with R134a as it achieves larger COP, exergy efficiency, and cooling capacity by 14%, 3.43%, and 20%, respectively.
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assessment of propane commercial butane mixtures as possible alternatives to r134a in domestic Refrigerators
International Conference on Aerospace Sciences and Aviation Technology, 2011Co-Authors: M Fatouh, El M KafafyAbstract:The possibility of using hydrocarbon mixtures as working fluids to replace R134a in domestic Refrigerators has been evaluated through a simulation analysis in the present work. Performance characteristics of domestic Refrigerators were predicted over a wide range of evaporation temperatures (-35 to -10°C) and condensation temperatures (40 to 60°C) for various working fluids such as R134a, propane, commercial butane and propane/iso-butane/n-butane mixture with various propane mass fractions. Performance characteristics of the considered domestic refrigerator was identified by the coefficient of performance (COP), volumetric cooling capacity, cooling capacity, condenser capacity, input power to the compressor, discharge temperature, pressure ratio and the refrigerant mass flow rate. Results showed that pure propane could not be used as a drop-in replacement for R134a in domestic Refrigerators because of its high operating pressures and low COP. Commercial butane yields many desrirable characteristics, but requires compressor change. Coefficient of performance of the domestic refrigerator using a ternary hydrocarbon mixture with propane mass fraction from 0.5 to 0.7 is higher than that of R134a. Comparison among the considered working fluids confirmed that average refrigerant mass flow rate of propoane/commercial butane mixture is 50% lqwer than that of R134a. Also, results indicated that R134a and propoane/commercial butane mixture of 60% propane mass concentration have approximately the same values of saturation pressure, compressor discharge temperature, condenser heat load, input power, cooling capacity and volumetric cooling capacity. However, the pressure ratio of the hydrocarbon mixture with 60% propane is lower than that of R134a by about 11.1%. Finally, the reported results confirmed that the propane/iso-butane/n-butane mixture with 60% propane is the best drop-in replacement for R134a in domestic Refrigerators under normal, subtropical and tropical operating conditions.
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assessment of propane commercial butane mixtures as possible alternatives to r134a in domestic Refrigerators
Energy Conversion and Management, 2006Co-Authors: M Fatouh, El M KafafyAbstract:Abstract The possibility of using hydrocarbon mixtures as working fluids to replace R134a in domestic Refrigerators has been evaluated through a simulation analysis in the present work. The performance characteristics of domestic Refrigerators were predicted over a wide range of evaporation temperatures (−35 to −10 °C) and condensation temperatures (40–60 °C) for various working fluids such as R134a, propane, commercial butane and propane/iso-butane/ n -butane mixtures with various propane mass fractions. The performance characteristics of the considered domestic refrigerator were identified by the coefficient of performance (COP), volumetric cooling capacity, cooling capacity, condenser capacity, input power to compressor, discharge temperature, pressure ratio and refrigerant mass flow rate. The results showed that pure propane could not be used as a drop in replacement for R134a in domestic Refrigerators because of its high operating pressures and low COP. Commercial butane yields many desirable characteristics but requires a compressor change. The coefficient of performance of the domestic refrigerator using a ternary hydrocarbon mixture with propane mass fractions from 0.5 to 0.7 is higher than that of R134a. Comparison among the considered working fluids confirmed that the average refrigerant mass flow rate of the propoane/commercial butane mixture is 50% lower than that of R134a. Also, the results indicated that R134a and the propoane/commercial butane mixture with 60% propane mass concentration have approximately the same values of saturation pressure, compressor discharge temperature, condenser heat load, input power, cooling capacity and volumetric cooling capacity. However, the pressure ratio of the hydrocarbon mixture with 60% propane is lower than that of R134a by about 11.1%. Finally, the reported results confirmed that the propane/iso-butane/ n -butane mixture with 60% propane is the best drop in replacement for R134a in domestic Refrigerators under normal, subtropical and tropical operating conditions.
José Miguel Mateos Roco - One of the best experts on this subject based on the ideXlab platform.
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Optimal low symmetric dissipation Carnot engines and Refrigerators
Physical Review E, 2012Co-Authors: C. De Tomas, A. Calvo Hernández, José Miguel Mateos RocoAbstract:A unified optimization criterion for Carnot engines and Refrigerators is proposed. It consists of maximizing the product of the heat absorbed by the working system times the efficiency per unit time of the device, either the engine or the refrigerator. This criterion can be applied to both low symmetric dissipation Carnot engines and Refrigerators. For engines the criterion coincides with the maximum power criterion and then the Curzon-Ahlborn efficiency ${\ensuremath{\eta}}_{\mathrm{CA}}=1\ensuremath{-}\sqrt{{T}_{c}/{T}_{h}}$ is recovered, where ${T}_{h}$ and ${T}_{c}$ are the temperatures of the hot and cold reservoirs, respectively [Esposito, Kawai, Lindenberg, and Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. For Refrigerators the criterion provides the counterpart of Curzon-Ahlborn efficiency for Refrigerators ${\ensuremath{\varepsilon}}_{\mathrm{CA}}=[1/(\sqrt{1\ensuremath{-}({T}_{c}/{T}_{h})}]\ensuremath{-}1$, first derived by Yan and Chen for the particular case of an endoreversible Carnot-type refrigerator with linear (Newtonian) finite heat transfer laws [Yan and Chen, J. Phys. D: Appl. Phys. 23, 136 (1990)].
El M Kafafy - One of the best experts on this subject based on the ideXlab platform.
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assessment of propane commercial butane mixtures as possible alternatives to r134a in domestic Refrigerators
International Conference on Aerospace Sciences and Aviation Technology, 2011Co-Authors: M Fatouh, El M KafafyAbstract:The possibility of using hydrocarbon mixtures as working fluids to replace R134a in domestic Refrigerators has been evaluated through a simulation analysis in the present work. Performance characteristics of domestic Refrigerators were predicted over a wide range of evaporation temperatures (-35 to -10°C) and condensation temperatures (40 to 60°C) for various working fluids such as R134a, propane, commercial butane and propane/iso-butane/n-butane mixture with various propane mass fractions. Performance characteristics of the considered domestic refrigerator was identified by the coefficient of performance (COP), volumetric cooling capacity, cooling capacity, condenser capacity, input power to the compressor, discharge temperature, pressure ratio and the refrigerant mass flow rate. Results showed that pure propane could not be used as a drop-in replacement for R134a in domestic Refrigerators because of its high operating pressures and low COP. Commercial butane yields many desrirable characteristics, but requires compressor change. Coefficient of performance of the domestic refrigerator using a ternary hydrocarbon mixture with propane mass fraction from 0.5 to 0.7 is higher than that of R134a. Comparison among the considered working fluids confirmed that average refrigerant mass flow rate of propoane/commercial butane mixture is 50% lqwer than that of R134a. Also, results indicated that R134a and propoane/commercial butane mixture of 60% propane mass concentration have approximately the same values of saturation pressure, compressor discharge temperature, condenser heat load, input power, cooling capacity and volumetric cooling capacity. However, the pressure ratio of the hydrocarbon mixture with 60% propane is lower than that of R134a by about 11.1%. Finally, the reported results confirmed that the propane/iso-butane/n-butane mixture with 60% propane is the best drop-in replacement for R134a in domestic Refrigerators under normal, subtropical and tropical operating conditions.
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assessment of propane commercial butane mixtures as possible alternatives to r134a in domestic Refrigerators
Energy Conversion and Management, 2006Co-Authors: M Fatouh, El M KafafyAbstract:Abstract The possibility of using hydrocarbon mixtures as working fluids to replace R134a in domestic Refrigerators has been evaluated through a simulation analysis in the present work. The performance characteristics of domestic Refrigerators were predicted over a wide range of evaporation temperatures (−35 to −10 °C) and condensation temperatures (40–60 °C) for various working fluids such as R134a, propane, commercial butane and propane/iso-butane/ n -butane mixtures with various propane mass fractions. The performance characteristics of the considered domestic refrigerator were identified by the coefficient of performance (COP), volumetric cooling capacity, cooling capacity, condenser capacity, input power to compressor, discharge temperature, pressure ratio and refrigerant mass flow rate. The results showed that pure propane could not be used as a drop in replacement for R134a in domestic Refrigerators because of its high operating pressures and low COP. Commercial butane yields many desirable characteristics but requires a compressor change. The coefficient of performance of the domestic refrigerator using a ternary hydrocarbon mixture with propane mass fractions from 0.5 to 0.7 is higher than that of R134a. Comparison among the considered working fluids confirmed that the average refrigerant mass flow rate of the propoane/commercial butane mixture is 50% lower than that of R134a. Also, the results indicated that R134a and the propoane/commercial butane mixture with 60% propane mass concentration have approximately the same values of saturation pressure, compressor discharge temperature, condenser heat load, input power, cooling capacity and volumetric cooling capacity. However, the pressure ratio of the hydrocarbon mixture with 60% propane is lower than that of R134a by about 11.1%. Finally, the reported results confirmed that the propane/iso-butane/ n -butane mixture with 60% propane is the best drop in replacement for R134a in domestic Refrigerators under normal, subtropical and tropical operating conditions.
C. De Tomas - One of the best experts on this subject based on the ideXlab platform.
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Optimal low symmetric dissipation Carnot engines and Refrigerators
Physical Review E, 2012Co-Authors: C. De Tomas, A. Calvo Hernández, José Miguel Mateos RocoAbstract:A unified optimization criterion for Carnot engines and Refrigerators is proposed. It consists of maximizing the product of the heat absorbed by the working system times the efficiency per unit time of the device, either the engine or the refrigerator. This criterion can be applied to both low symmetric dissipation Carnot engines and Refrigerators. For engines the criterion coincides with the maximum power criterion and then the Curzon-Ahlborn efficiency ${\ensuremath{\eta}}_{\mathrm{CA}}=1\ensuremath{-}\sqrt{{T}_{c}/{T}_{h}}$ is recovered, where ${T}_{h}$ and ${T}_{c}$ are the temperatures of the hot and cold reservoirs, respectively [Esposito, Kawai, Lindenberg, and Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. For Refrigerators the criterion provides the counterpart of Curzon-Ahlborn efficiency for Refrigerators ${\ensuremath{\varepsilon}}_{\mathrm{CA}}=[1/(\sqrt{1\ensuremath{-}({T}_{c}/{T}_{h})}]\ensuremath{-}1$, first derived by Yan and Chen for the particular case of an endoreversible Carnot-type refrigerator with linear (Newtonian) finite heat transfer laws [Yan and Chen, J. Phys. D: Appl. Phys. 23, 136 (1990)].
Dvira Segal - One of the best experts on this subject based on the ideXlab platform.
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cooling condition for multilevel quantum absorption Refrigerators
Physical Review E, 2019Co-Authors: Hava Meira Friedman, Dvira SegalAbstract:Models for quantum absorption Refrigerators serve as test beds for exploring concepts and developing methods in quantum thermodynamics. Here we depart from the minimal, ideal design and consider a generic multilevel model for a quantum absorption refrigerator, which potentially suffers from lossy processes. Based on a full-counting statistics approach, we derive a formal cooling condition for the refrigerator, which can be feasibly evaluated analytically and numerically. We exemplify our approach on a three-level model for a quantum absorption refrigerator that suffers from different forms of nonideality (heat leakage, competition between different cooling pathways) and examine the cooling current with different designs. This study assists in identifying the cooling window of imperfect thermal machines.
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coherence and decoherence in quantum absorption Refrigerators
Physical Review E, 2018Co-Authors: Michael Kilgour, Dvira SegalAbstract:Absorption Refrigerators transfer thermal energy from a cold reservoir to a hot reservoir using input energy from a third, so-called work reservoir. We examine the operation of quantum absorption Refrigerators when coherences between eigenstates survive in the steady state limit. In our model, the working medium comprises a discrete, four-level system. Several studies on related setups have demonstrated the performance-enhancing potential of steady-state eigenbasis quantum coherences. By contrast, in our model such coherences generally quench the cooling current in the refrigerator, while minimally affecting the coefficient of performance (cooling efficiency). We rationalize the behavior of the four-level refrigerator by studying three-level model systems for energy transport and refrigeration. Our calculations further illuminate the shortcomings of secular quantum master equations and the necessity of employing dynamical equations of motion that retain couplings between population and coherences.
