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J.J. Garcia Pabon
Institute in Mechanical Engineering, Federal University of Itajubá (UNIFEI), Av. BPS, 1303, Itajubá, CEP: 37500903, Brazil

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Review
Published: 23 May 2021 in Sustainability
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ORC technology is one of the most promising technologies for the use of residual energy in the generation of electrical energy, offering simple and environmentally friendly alternatives. In this field, the selection of working fluids plays an important role in the operation of the cycle, whether in terms of the energy efficiency or the minimization of environmental impacts. Therefore, in this paper, a comprehensive review is presented on the use of R1234yf refrigerant and its mixtures as working fluids in ORC systems. These fluids are used in low- and medium-temperature applications for the use of residual energy generated from solar energy, geothermal energy, and internal combustion engines. It was concluded that R1234yf and its mixtures are competitive as compared with conventional refrigerants used in ORC.

ACS Style

Juan García-Pabón; Dario Méndez-Méndez; Juan Belman-Flores; Juan Barroso-Maldonado; Ali Khosravi. A Review of Recent Research on the Use of R1234yf as an Environmentally Friendly Fluid in the Organic Rankine Cycle. Sustainability 2021, 13, 5864 .

AMA Style

Juan García-Pabón, Dario Méndez-Méndez, Juan Belman-Flores, Juan Barroso-Maldonado, Ali Khosravi. A Review of Recent Research on the Use of R1234yf as an Environmentally Friendly Fluid in the Organic Rankine Cycle. Sustainability. 2021; 13 (11):5864.

Chicago/Turabian Style

Juan García-Pabón; Dario Méndez-Méndez; Juan Belman-Flores; Juan Barroso-Maldonado; Ali Khosravi. 2021. "A Review of Recent Research on the Use of R1234yf as an Environmentally Friendly Fluid in the Organic Rankine Cycle." Sustainability 13, no. 11: 5864.

Journal article
Published: 21 March 2021 in Sustainability
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This paper presents a distributed mathematical model for a carbon dioxide direct expansion solar-assisted heat pump used to heat bath water. The main components are a gas cooler, a needle valve, an evaporator/collector, and a compressor. To develop the heat exchange models, mass, energy, and momentum balances were used. The model was validated for transient as well as steady state conditions using experimental data. A reasonably good agreement was observed between the predicted temperatures and experimental data. The simulations showed that the time step required to demonstrate the behavior of the heat pump in the transient regime is greater than the time step required for the steady state. The results obtained with the mathematical model revealed that a reduction in the water mass flow rate results in an increase in the water outlet temperature. In addition, when the carbon dioxide mass flow rate is reduced, the compressor inlet and outlet temperatures increase as well as the water outlet temperature.

ACS Style

Hélio Diniz; Tiago Paulino; Juan Pabon; Antônio Maia; Raphael Oliveira. Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating. Sustainability 2021, 13, 3464 .

AMA Style

Hélio Diniz, Tiago Paulino, Juan Pabon, Antônio Maia, Raphael Oliveira. Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating. Sustainability. 2021; 13 (6):3464.

Chicago/Turabian Style

Hélio Diniz; Tiago Paulino; Juan Pabon; Antônio Maia; Raphael Oliveira. 2021. "Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating." Sustainability 13, no. 6: 3464.

Journal article
Published: 14 January 2021 in International Journal of Refrigeration
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In the past decades, combined solar energy with heat pump systems has been one of the very widespread ways to improve the efficiency of conventional heat pumps. In that way, this paper presents an experimental analysis of the influence of environmental conditions in a small size DX-SAHP operating with CO2 as refrigeration fluid to heat water. The variation of the water inlet temperature, the solar radiation flux and the relative humidity are analyzed and 88 different experimental results are presented. To support the analysis, a thermographic camera was also used. The results show that the gas cooler outlet pressure and temperature are strongly influenced by the water inlet temperature. As the water inlet temperature increases, the gas cooler outlet pressure and temperature increase, and consequently the COP decreases. The COP decreases in 45.8% for the variation of the water inlet temperature to 15–35 oC. The variation of the solar radiation of 876.9–30.17 W.m-2 presents a reduction of performance in about 30%. For the same conditions for the water heat exchange, the pressure ratio of the cycle decreases with an augment on the solar radiation flux. In addition, the COP is higher in 6% for a change in the mean relative humidity of 31.6–55.8 %.

ACS Style

Willian M. Duarte; Sabrina N. Rabelo; Tiago F. Paulino; Juan J.G. Pabón; Luiz Machado. Experimental performance analysis of a CO2 direct-expansion solar assisted heat pump water heater. International Journal of Refrigeration 2021, 125, 52 -63.

AMA Style

Willian M. Duarte, Sabrina N. Rabelo, Tiago F. Paulino, Juan J.G. Pabón, Luiz Machado. Experimental performance analysis of a CO2 direct-expansion solar assisted heat pump water heater. International Journal of Refrigeration. 2021; 125 ():52-63.

Chicago/Turabian Style

Willian M. Duarte; Sabrina N. Rabelo; Tiago F. Paulino; Juan J.G. Pabón; Luiz Machado. 2021. "Experimental performance analysis of a CO2 direct-expansion solar assisted heat pump water heater." International Journal of Refrigeration 125, no. : 52-63.

Review article
Published: 20 June 2020 in International Journal of Refrigeration
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HFC refrigerants as R134a, R404A, R407C and R410A are commonly used in heating, air conditioning and refrigeration (HACR) systems since Kyoto protocol. However, they are phased-out due to their high global warming potential (GWP). There are various options to replace high GWP refrigerants, among all hydrofluorolefin (HFO) fluids, such as R1234yf, represents an excellent alternative. With GWP <1, R1234yf is a promising substitute for R134a. This paper presents the most relevant researches concerning the application of R1234yf in the last decade. This review paper regroups experimental and theoretical studies which assess the performance of pure R1234yf as working fluid of the compression systems such as mobile and residential air conditioning, air and water heat pump, domestic refrigerator and freezer. Studies depict that R1234yf can be recommended for small-scale systems instead of R134a, but an optimization process is necessary to achieve the optimum operating conditions.

ACS Style

Juan J.G. Pabon; Ali Khosravi; J.M. Belman-Flores; Luiz Machado; Remi Revellin. Applications of refrigerant R1234yf in heating, air conditioning and refrigeration systems: A decade of researches. International Journal of Refrigeration 2020, 118, 104 -113.

AMA Style

Juan J.G. Pabon, Ali Khosravi, J.M. Belman-Flores, Luiz Machado, Remi Revellin. Applications of refrigerant R1234yf in heating, air conditioning and refrigeration systems: A decade of researches. International Journal of Refrigeration. 2020; 118 ():104-113.

Chicago/Turabian Style

Juan J.G. Pabon; Ali Khosravi; J.M. Belman-Flores; Luiz Machado; Remi Revellin. 2020. "Applications of refrigerant R1234yf in heating, air conditioning and refrigeration systems: A decade of researches." International Journal of Refrigeration 118, no. : 104-113.

Journal article
Published: 13 May 2020 in Renewable Energy
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Generally, the majority of the linear concentrating photovoltaic (LCPV) systems incorporated with active cooling systems use liquid water pump loop or conventional vapor compression refrigeration system. In this study, a new cooling system, so-called two-phase mechanical pumped loop (TMPL), is proposed to be used with LCPV system. The excess heat from photovoltaic (PV) cell is used to heat up water stored in a tank for residential purposes. The case study is Bogota in Colombia and we develop a dynamic simulation model for the LCPV-TMPL system. The design parameters of the TMPL system are the flow volumetric rate and saturation temperature of the refrigerant as well as the tube length of the condenser. Moreover, low global warming potential (GWP) refrigerants such as R1234yf and R1234ze(E) were evaluated, both showing the same performance compared to R134a. The results showed that the use of TMPL system to eliminate the generated heat of PV cell improves its temperature stability and efficiency. It also shows how the proposed model can be used to design the thermal/photovoltaic system for a local, showing also the expected performance before the system installation. In the case study region, the LCPV-TMPL system, using four PV cells with 5 m × 10 mm, produces power with an average monthly of 2 kW with a peak of 5 kW under average and peak monthly solar radiation of 400 W/m2 and 600 W/m2, respectively. The storage tank can heat up 2.2 m³ water per day from 8 °C to approximately 28 °C, in an average sense. This means that the LCPV-TMPL system could save 9000 kWh and 1900 kWh per year in electricity and thermal energies (water heating). This system can be used locally with low or medium solar radiation and cold weather.

ACS Style

Juan J.G. Pabon; Ali Khosravi; Mohammad Malekan; Oscar R. Sandoval. Modeling and energy analysis of a linear concentrating photovoltaic system cooled by two-phase mechanical pumped loop system. Renewable Energy 2020, 157, 273 -289.

AMA Style

Juan J.G. Pabon, Ali Khosravi, Mohammad Malekan, Oscar R. Sandoval. Modeling and energy analysis of a linear concentrating photovoltaic system cooled by two-phase mechanical pumped loop system. Renewable Energy. 2020; 157 ():273-289.

Chicago/Turabian Style

Juan J.G. Pabon; Ali Khosravi; Mohammad Malekan; Oscar R. Sandoval. 2020. "Modeling and energy analysis of a linear concentrating photovoltaic system cooled by two-phase mechanical pumped loop system." Renewable Energy 157, no. : 273-289.

Review article
Published: 15 November 2019 in International Journal of Refrigeration
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The current European F-gas regulation establishes restrictions in the use of fluoride refrigerants with a high global warming potential (GWP) in applications of refrigeration and air conditioning (RAC) systems. Moreover, a gradual limitation on the GWP weight of the fluoride refrigerants placed on the market is ongoing and will end with approximately one-fifth of today's offer. In this context, many of the RAC systems operate with refrigerants R134a, R404A, and R410A that have GWP values of 1300, 3943 and 2088, respectively, are being forced to be replaced by environmentally friendly alternatives, like hydrofluoroolefin (HFO) refrigerants and their mixtures with hydrofluorocarbons (HFC), which can be designed to present intermediate characteristics and become the ideal candidate many RAC applications. This work presents the most recent HFC/HFO/HC/R744 refrigerant mixture options for an alternative to the refrigerants mentiond above and compares their energetic and performance with the early developed mixture prototypes.

ACS Style

Y. Heredia-Aricapa; J.M. Belman-Flores; A. Mota-Babiloni; J. Serrano-Arellano; Juan J. García-Pabón. Overview of low GWP mixtures for the replacement of HFC refrigerants: R134a, R404A and R410A. International Journal of Refrigeration 2019, 111, 113 -123.

AMA Style

Y. Heredia-Aricapa, J.M. Belman-Flores, A. Mota-Babiloni, J. Serrano-Arellano, Juan J. García-Pabón. Overview of low GWP mixtures for the replacement of HFC refrigerants: R134a, R404A and R410A. International Journal of Refrigeration. 2019; 111 ():113-123.

Chicago/Turabian Style

Y. Heredia-Aricapa; J.M. Belman-Flores; A. Mota-Babiloni; J. Serrano-Arellano; Juan J. García-Pabón. 2019. "Overview of low GWP mixtures for the replacement of HFC refrigerants: R134a, R404A and R410A." International Journal of Refrigeration 111, no. : 113-123.

Journal article
Published: 10 September 2019 in Energy Conversion and Management
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Solar energy is a renewable energy resources that is available across the world. A solar dish/Stirling system means a parabolic dish concentrator and a Stirling engine combined to generate mechanical and/or electrical output power. In this system, the input energy of Stirling engine is provided by sunlight as a source of heat. This study presents the effect of different variables on the power generation and efficiency of the system. In addition, artificial intelligence approach is employed to model a solar dish/Stirling system. For this target, a huge dataset was provided by considering a wide range of input variables. The intelligent methods are group method of data handling (GMDH) type neural network, adaptive neuro-fuzzy inference system (ANFIS) and multilayer perceptron (MLP) neural network (ANN). The MLP and ANFIS are optimized with particle swarm optimization (PSO) and genetic algorithm (GA). The intelligent methods are trained with inputs and targets. The considered input parameters are the ratio of focal point to dish diameter, hour of day, solar radiation, geometric concentration factor and working gas specific constant. The power generation, global efficiency, heat used to run the Stirling cycle, hot Stirling chamber temperature and engine speed are selected to be the targets. The results depict that the intelligent methods operate successfully for energy modeling of the solar dish/Stirling system and the statistical indicators illustrate that the ANFIS-PSO method performs better than the other developed methods.

ACS Style

Ali Khosravi; Sanna Syri; Juan J.G. Pabon; Oscar R. Sandoval; Bryan Castro Caetano; Miguel H. Barrientos. Energy modeling of a solar dish/Stirling by artificial intelligence approach. Energy Conversion and Management 2019, 199, 112021 .

AMA Style

Ali Khosravi, Sanna Syri, Juan J.G. Pabon, Oscar R. Sandoval, Bryan Castro Caetano, Miguel H. Barrientos. Energy modeling of a solar dish/Stirling by artificial intelligence approach. Energy Conversion and Management. 2019; 199 ():112021.

Chicago/Turabian Style

Ali Khosravi; Sanna Syri; Juan J.G. Pabon; Oscar R. Sandoval; Bryan Castro Caetano; Miguel H. Barrientos. 2019. "Energy modeling of a solar dish/Stirling by artificial intelligence approach." Energy Conversion and Management 199, no. : 112021.

Journal article
Published: 28 August 2019 in Applied Thermal Engineering
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Compressed air energy storage (CAES) is a hopeful technology to overcome the intermittency of renewable energy systems and meet the high peak load demand. The objective of this study is to propose a double pipe heat exchanger (DPHX) working with CuO/water nanofluid in order to cool the compressed air before cavern in a small-scale CAES system. A new design of DPHX by considering different internal tube geometry (nine configurations) is proposed. To achieve these targets, a transient model for simulating the technical demeanor of the CAES system is developed. After simulating the behavior of the CAES system, DPHX is modeled by computational fluid dynamics (CFD) to evaluate the outcome of nanofluid as well as geometry design on the DPHX performance. The pressure drop is unchanged for all finned tube at higher Reynolds numbers. The numerical analysis through mathematical modeling of the charging process of the cavern denotes the effect of length and mass flow rate of the secondary fluid in the DPHX. The results illustrate that by enhancing the mass flow of the secondary fluid, the cavern temperature declines. The pressure inside the cavern has a small dependence on its temperature. The cavern pressure is invariant by increasing the secondary fluid flow. For proposed DPHX, the convective heat transfer coefficient increased up to 22% for cold fluid considering tube with four fins (air/nanofluid+ finned tube (w=3.5 mm and H=1.0 mm)) and compared to the smooth tube. In addition, around 17% enhancement in convective heat transfer coefficient was achieved using tube with eight fins and with air/nanofluid as the working fluid (case with w=3.5 mm and H=1.0 mm), compared to tube with four fins. This shows the capability of the proposed finned tube along with the utilization of the nanofluid to increase the heat exchanger performance.

ACS Style

A. Khosravi; H. Campos; M. Malekan; R.O. Nunes; M.E.H. Assad; L. Machado; J.J. Garcia Pabon. Performance improvement of a double pipe heat exchanger proposed in a small-scale CAES system: An innovative design. Applied Thermal Engineering 2019, 162, 114315 .

AMA Style

A. Khosravi, H. Campos, M. Malekan, R.O. Nunes, M.E.H. Assad, L. Machado, J.J. Garcia Pabon. Performance improvement of a double pipe heat exchanger proposed in a small-scale CAES system: An innovative design. Applied Thermal Engineering. 2019; 162 ():114315.

Chicago/Turabian Style

A. Khosravi; H. Campos; M. Malekan; R.O. Nunes; M.E.H. Assad; L. Machado; J.J. Garcia Pabon. 2019. "Performance improvement of a double pipe heat exchanger proposed in a small-scale CAES system: An innovative design." Applied Thermal Engineering 162, no. : 114315.

Journal article
Published: 18 May 2019 in International Journal of Refrigeration
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In this study, the two-phase pressure drop of R1234yf refrigerant (as an alternative to R134a) in a smooth horizontal tube is investigated. Tests are carried out and under several conditions of vapor quality (0% to 100%), mass velocity (200, 300 and 400 kg/m²s), heat flux (0, 7 and 14 kW/m²) and evaporation temperatures (20°C and 30°C). The internal diameters tested are 3.2 mm, 4.8 mm, 6.4 mm and 8.0 mm. A comparison of pressure drop between R1234yf and R134a is also carried out. The results demonstrate that the two-phase pressure gradient of R1234yf is approximately 20% lower than that of R134a. The experimental data is compared with 19 correlations from the literature. From this comparison, it is concluded that the experimental data are in accordance with the correlation proposed by Xu and Fang with a mean absolute error of 20% and with approximately 65% of the data predicted within a ± 30% error band.

ACS Style

Juan Garcia Pabon; Ali Khosravi; Raphael Nunes; Luiz Machado. Experimental investigation of pressure drop during two-phase flow of R1234yf in smooth horizontal tubes with internal diameters of 3.2 mm to 8.0 mm. International Journal of Refrigeration 2019, 104, 426 -436.

AMA Style

Juan Garcia Pabon, Ali Khosravi, Raphael Nunes, Luiz Machado. Experimental investigation of pressure drop during two-phase flow of R1234yf in smooth horizontal tubes with internal diameters of 3.2 mm to 8.0 mm. International Journal of Refrigeration. 2019; 104 ():426-436.

Chicago/Turabian Style

Juan Garcia Pabon; Ali Khosravi; Raphael Nunes; Luiz Machado. 2019. "Experimental investigation of pressure drop during two-phase flow of R1234yf in smooth horizontal tubes with internal diameters of 3.2 mm to 8.0 mm." International Journal of Refrigeration 104, no. : 426-436.

Journal article
Published: 14 May 2019 in Journal of Heat Transfer
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In this study, thermal resistance of a closed-loop oscillating heat pipe (OHP) is investigated using experimental tests and artificial intelligence methods. For this target, γFe2O3 and Fe3O4 nanoparticles are mixed with the base fluid. Also, intelligent models are developed to predict the thermal resistance of the OHP. These models are developed based on the heat input into evaporator section, the thermal conductivity of working fluids, and the ratio of the inner diameter to length of OHP. The intelligent methods are multilayer feed-forward neural network (MLFFNN), adaptive neuro-fuzzy inference system (ANFIS) and group method of data handling (GMDH) type neural network. Thermal resistance of the heat pipe (as a measure of thermal performance) is considered as the target. The results showed that using the nanofluids as working fluid in the OHP decreased the thermal resistance, where this decrease for Fe3O4/water nanofluid was more than that of γFe2O3/water. The intelligent models also predicted successfully the thermal resistance of OHP with a correlation coefficient close to 1. The root-mean-square error (RMSE) for MLFFNN, ANFIS, and GMDH models was obtained as 0.0508, 0.0556, and 0.0569 (°C/W) (for the test data), respectively.

ACS Style

Mohammad Malekan; Ali Khosravi; Hamid Reza Goshayeshi; M. E. H. Assad; J. J. Garcia Pabon. Thermal Resistance Modeling of Oscillating Heat Pipes for Nanofluids by Artificial Intelligence Approach. Journal of Heat Transfer 2019, 141, 072402 .

AMA Style

Mohammad Malekan, Ali Khosravi, Hamid Reza Goshayeshi, M. E. H. Assad, J. J. Garcia Pabon. Thermal Resistance Modeling of Oscillating Heat Pipes for Nanofluids by Artificial Intelligence Approach. Journal of Heat Transfer. 2019; 141 (7):072402.

Chicago/Turabian Style

Mohammad Malekan; Ali Khosravi; Hamid Reza Goshayeshi; M. E. H. Assad; J. J. Garcia Pabon. 2019. "Thermal Resistance Modeling of Oscillating Heat Pipes for Nanofluids by Artificial Intelligence Approach." Journal of Heat Transfer 141, no. 7: 072402.

Journal article
Published: 10 May 2019 in International Journal of Refrigeration
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Void fraction is an important parameter to design and simulate thermal systems involving two-phase flows. In this research, an experimental investigation of the void fraction in adiabatic two-phase flow of R1234yf in horizontal and smooth tubes with an internal diameter of 4.8 mm was carried out. For the experimental tests, the vapor quality ranges from 0.1 to 1 while two saturation temperatures (15 and 25°C) and two mass flow rates (180 and 280 kg.m−2s−1) are investigated. The quick-closing valve(s) method is used to measure the volumetric void fraction. Tests are also undertaken with R134a used as a reference in this study. The results highlight that the void fraction of R1234yf is 5% lower than that for R134a. In addition, the experimental data of R1234yf were compared against seven correlations from the literature: the Baroczy and the Hughmark correlations were shown to provide the best prediction, with a mean absolute error of 2% and 3.2%, respectively.

ACS Style

Juan J. Garcia Pabon; Leandro C. Pereira; Gleberson Humia; Ali Khosravi; Rémi Revellin; Jocelyn Bonjour; Luiz Machado. Experimental study on the void fraction during two-phase flow of R1234yf in smooth horizontal tubes. International Journal of Refrigeration 2019, 104, 103 -112.

AMA Style

Juan J. Garcia Pabon, Leandro C. Pereira, Gleberson Humia, Ali Khosravi, Rémi Revellin, Jocelyn Bonjour, Luiz Machado. Experimental study on the void fraction during two-phase flow of R1234yf in smooth horizontal tubes. International Journal of Refrigeration. 2019; 104 ():103-112.

Chicago/Turabian Style

Juan J. Garcia Pabon; Leandro C. Pereira; Gleberson Humia; Ali Khosravi; Rémi Revellin; Jocelyn Bonjour; Luiz Machado. 2019. "Experimental study on the void fraction during two-phase flow of R1234yf in smooth horizontal tubes." International Journal of Refrigeration 104, no. : 103-112.

Journal article
Published: 09 May 2019 in Applied Thermal Engineering
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Heat management by means of two-phase mechanically pumped loop (TMPL) possesses promising advantages such as long-distance heat transport, high heat density and good temperature control. Knowledge of the fluid charge has great importance for TMPL system efficiency. The present work is a theoretical/experimental study on the refrigerant charge in TMPL system using R134a and R1234yf refrigerants. The mass of refrigerant in the TMPL system was measured for several cooling capacities. The effects of vapor quality in the evaporator (varying from 0.1 to 1), mass flux (300kg.s-1m-2 and 400kg.s-1m-2), and saturation temperature (25°C and 30°C) on refrigerant charge in the TMPL were experimentally investigated. About 70 experimental points were analyzed and compared with a theoretical model employing eight different prediction tools for the determination of the void fraction. The best results were obtained by Zivi and Hughmark correlations with mean absolute errors of 12% and 13%, respectively.

ACS Style

Leandro Pereira; Gleberson Humia; Ali Khosravi; Rémi Revellin; Jocelyn Bonjour; Luiz Machado; Juan J. Garcia Pabon. A study on the fluid refrigerant charge in a two-phase mechanically pumped loop system using R134a and R1234yf. Applied Thermal Engineering 2019, 158, 113727 .

AMA Style

Leandro Pereira, Gleberson Humia, Ali Khosravi, Rémi Revellin, Jocelyn Bonjour, Luiz Machado, Juan J. Garcia Pabon. A study on the fluid refrigerant charge in a two-phase mechanically pumped loop system using R134a and R1234yf. Applied Thermal Engineering. 2019; 158 ():113727.

Chicago/Turabian Style

Leandro Pereira; Gleberson Humia; Ali Khosravi; Rémi Revellin; Jocelyn Bonjour; Luiz Machado; Juan J. Garcia Pabon. 2019. "A study on the fluid refrigerant charge in a two-phase mechanically pumped loop system using R134a and R1234yf." Applied Thermal Engineering 158, no. : 113727.

Journal article
Published: 01 May 2019 in Respuestas
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The electrolyzers work through an electrochemical process, their derivatives (H2,O2 , and HHO) are used as enriching fuels due to the electrolysis of water, being cleaner than gasoline and diesel. This article presents the dynamic model of an alkaline electrolyzer that uses an electrolyte ( KOH o NaHCO3) dissolved in distilled water to accelerate the production of oxyhydrogen (HHO). The model shows the phase change that occurs inside the electrolytic cell. The EES® software was used to determine the values ​​of enthalpy, entropy, and free energy that vary during the electrochemical reaction; the equations were simulated in Matlab-Simulink® to observe their dynamic behavior. The Simulations presented varying every 5 g the electrolyte until reaching 20 g. The flow rate of HHO with potassium hydroxide (20 g) is higher than 0.02 L / s, and with sodium bicarbonate (20 g) it is above 0.0006 L / s, confirming what the literature of alkaline cells state, that the most efficient electrolyte for its energy conversion is KOH.

ACS Style

Erick Daniel Rincón Castrillo; José Ricardo Bermúdez Santaella; Luis Emilio Vera Duarte; Juan José García Pabón. Modeling and simulation of an electrolyser for the production of HHO in Matlab- Simulink®. Respuestas 2019, 24, 6 -15.

AMA Style

Erick Daniel Rincón Castrillo, José Ricardo Bermúdez Santaella, Luis Emilio Vera Duarte, Juan José García Pabón. Modeling and simulation of an electrolyser for the production of HHO in Matlab- Simulink®. Respuestas. 2019; 24 (2):6-15.

Chicago/Turabian Style

Erick Daniel Rincón Castrillo; José Ricardo Bermúdez Santaella; Luis Emilio Vera Duarte; Juan José García Pabón. 2019. "Modeling and simulation of an electrolyser for the production of HHO in Matlab- Simulink®." Respuestas 24, no. 2: 6-15.

Journal article
Published: 01 May 2019 in Respuestas
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This article is intended to draw attention of the community in general to the changes that have taken place in refrigeration and air conditioning industry of the HFC refrigerants currently used. The HFCs are not Ozone-depleting substances, but the some HFCs are greenhouse gases with very high potential for global warming (GWPs). Thus, more than 150 countries sign up the Kigali Amendment in 2016, establishing the decreasing of the production and consumption of the HFCs. This paper briefly describes the problems surrounding the HFCs and summarizes the fluids considered as alternatives for the main HFCs used in refrigeration systems presented in the scientific literature. In addition, the outlook and the current situation of the HFC withdrawal process in Colombia are analyzed.

ACS Style

Juan José García Pabón. Phase-out of high GWP refrigerants in refrigeration systems: Status of process in Colombia. Respuestas 2019, 24, 65 -74.

AMA Style

Juan José García Pabón. Phase-out of high GWP refrigerants in refrigeration systems: Status of process in Colombia. Respuestas. 2019; 24 (2):65-74.

Chicago/Turabian Style

Juan José García Pabón. 2019. "Phase-out of high GWP refrigerants in refrigeration systems: Status of process in Colombia." Respuestas 24, no. 2: 65-74.

Journal article
Published: 13 April 2019 in Solar Energy
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An important step during a project of a heat pump system is choosing a more suitable refrigerant. This paper presents a comparative study among refrigerants for a small direct expansion solar assisted heat pump (DX-SAHP). The mathematical model used in this study is presented in detail and validated from an experimental setup. The R134a is the reference and the refrigerants with low GWP are R290, R600a, R744 and R1234yf. The results show that R290 has better COP than others refrigerants for solar radiation between 300 W/m2 and 700 W/m2, as well as for environment temperature between 10 °C and 35 °C. On the other hand, for solar radiation less than 50 W/m2, the R134a has better COP than R290. TEWI (Total Equivalent Warming Impact) analysis indicates that the indirect emission is the most important effect, and then, the TEWI results almost followed the COP outcome. A parametric analysis was conducted to evaluate the influence of the CO2 emission factor for producing electricity. In countries with higher emission factor, the refrigerant with the best COP has the best TEWI. The influence of wind speed and ambient temperature in COP of a DX-SAHP using R290 were more relevant in low solar radiation.

ACS Style

Willian M. Duarte; Tiago F. Paulino; Juan Jose Garcia Pabon; Samer Sawalha; Luiz Machado. Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water. Solar Energy 2019, 184, 527 -538.

AMA Style

Willian M. Duarte, Tiago F. Paulino, Juan Jose Garcia Pabon, Samer Sawalha, Luiz Machado. Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water. Solar Energy. 2019; 184 ():527-538.

Chicago/Turabian Style

Willian M. Duarte; Tiago F. Paulino; Juan Jose Garcia Pabon; Samer Sawalha; Luiz Machado. 2019. "Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water." Solar Energy 184, no. : 527-538.

Journal article
Published: 15 May 2018 in International Journal of Refrigeration
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This study is developed to evaluate the possibility of R1234yf to be a drop-in replacement for a pre-designed system with R134a, including the characterization of control system in a vapor compression system. The control algorithms are required for regulating the refrigerant flow rate into the evaporator and their control parameters depend intrinsically on refrigerant fluid. This paper presents a comparison of the effects of R134a and R1234yf refrigerants on the transient response of an evaporator operating with water as secondary fluid (counter-flow). The dynamic heat exchanger distributed model combines principles of thermodynamics, heat and mass transfer with empirical correlations, which are proposed in the literature, in order to compute the void fraction, pressure drop and heat transfer in two-phase flow. Experimental tests are carried out on a fixed refrigeration system for cooling capacity less than 3 kW, with constant condensation conditions, variable evaporating temperature and compressor speed to validate the model. The results demonstrated that a good agreement between simulation results and experimental data was achieved. The evaporation temperature data were within ± 1°C error band. Furthermore, comparative simulations between the refrigerants R-134a and R-1234yf exhibited a similar dynamic behavior during a step at the inlet mass flow rate, and the gain and time constant for superheat control were not considerably modified. Therefore, the refrigerant changing does not demand many changes in the expansion device control strategy.

ACS Style

Juan Garcia; Thiago Ali; Willian Moreira Duarte; Ali Khosravi; Luiz Machado. Comparison of transient response of an evaporator model for water refrigeration system working with R1234yf as a drop-in replacement for R134a. International Journal of Refrigeration 2018, 91, 211 -222.

AMA Style

Juan Garcia, Thiago Ali, Willian Moreira Duarte, Ali Khosravi, Luiz Machado. Comparison of transient response of an evaporator model for water refrigeration system working with R1234yf as a drop-in replacement for R134a. International Journal of Refrigeration. 2018; 91 ():211-222.

Chicago/Turabian Style

Juan Garcia; Thiago Ali; Willian Moreira Duarte; Ali Khosravi; Luiz Machado. 2018. "Comparison of transient response of an evaporator model for water refrigeration system working with R1234yf as a drop-in replacement for R134a." International Journal of Refrigeration 91, no. : 211-222.

Journal article
Published: 01 April 2018 in Energy
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The goal of this study is to define and assess an off-grid hybrid renewable energy with hydrogen storage system. The system combines solar and wind energy, hydrogen production unit and fuel cell. This photovoltaic/wind hydrogen energy system focuses on a large scale system with constant electrical load and especially suitable for remote area applications. Energy, exergy and economic analysis are conducted for this system. The pattern of the produced power for the photovoltaic (PV) system and wind turbine with a dynamic model of solar and wind energy are determined. Also, components sizing of the proposed system is determined. Energy and exergy analysis of the PV system was reported the average of 12% and 16% for energy and exergy efficiencies, respectively. The average energy and exergy efficiencies of the wind turbine were obtained approximately 32% and 25%, respectively. The maximum exergy destruction for the PV system was obtained around 65%. Also, based on economic analysis, energy storage system was included 50% of the total investment.

ACS Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. Energy, exergy and economic analysis of a hybrid renewable energy with hydrogen storage system. Energy 2018, 148, 1087 -1102.

AMA Style

A. Khosravi, R.N.N. Koury, L. Machado, Juan Jose Garcia Pabon. Energy, exergy and economic analysis of a hybrid renewable energy with hydrogen storage system. Energy. 2018; 148 ():1087-1102.

Chicago/Turabian Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. 2018. "Energy, exergy and economic analysis of a hybrid renewable energy with hydrogen storage system." Energy 148, no. : 1087-1102.

Journal article
Published: 01 March 2018 in Applied Thermal Engineering
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The calculation of the pressure drop for two-phase flow in evaporation and condensation processes is required by a variety of design practices. In recent years, many correlations were developed in order to determine the pressure drop for two-phase flow. This process needs many experimental tests. Hence, in this study, it is proposed to apply machine learning algorithms (MLAs) to forecast the pressure drop for two-phase flow of R407C. Three methods of MLAs are developed with the purpose of pressure drop prediction in a smooth horizontal copper tube, for 4.5 mm and 8 mm inner diameter. These methods are multilayer feed-forward neural network (MLFFNN), support vector regression (SVR), and group method of data handling (GMDH) type neural network. Mass flux, tube diameter, saturation pressure, and vapor quality of the refrigerant are used as input variables of the models and the target is selected to be the pressure drop of evaporation. The results show that although the developed models can successfully predict the pressure drop of two-phase flow, MLFFNN and GMDH models outperform the SVR model in term of the correlation coefficient close to 1.

ACS Style

A. Khosravi; J.J.G. Pabon; R.N.N. Koury; L. Machado. Using machine learning algorithms to predict the pressure drop during evaporation of R407C. Applied Thermal Engineering 2018, 133, 361 -370.

AMA Style

A. Khosravi, J.J.G. Pabon, R.N.N. Koury, L. Machado. Using machine learning algorithms to predict the pressure drop during evaporation of R407C. Applied Thermal Engineering. 2018; 133 ():361-370.

Chicago/Turabian Style

A. Khosravi; J.J.G. Pabon; R.N.N. Koury; L. Machado. 2018. "Using machine learning algorithms to predict the pressure drop during evaporation of R407C." Applied Thermal Engineering 133, no. : 361-370.

Journal article
Published: 01 March 2018 in Journal of Cleaner Production
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Accurate forecasting of renewable energy sources plays a key role in their integration into the grid. This study proposes machine learning algorithms to predict the hourly solar irradiance. Forecasting models were developed based two types of the input data. The first one uses local time, temperature, pressure, wind speed, and relative humidity as input variables of the models (N1); the second one is the time-series prediction of solar irradiance (N2) (forecasting models only use from past time-series solar radiation values to estimate the future values). For this purpose, multilayer feed-forward neural network (MLFFNN), radial basis function neural network (RBFNN), support vector regression (SVR), fuzzy inference system (FIS) and adaptive neuro-fuzzy inference system (ANFIS) are developed. The results demonstrated that for the N1, SVR and MLFFNN models have the maximum performance to predict the solar irradiance with R = 0.9999 and 0.9795, respectively. For the N2, SVR, MLFFNN and ANFIS models have reported the correlation coefficient more than 0.95 for the testing dataset.

ACS Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. Prediction of hourly solar radiation in Abu Musa Island using machine learning algorithms. Journal of Cleaner Production 2018, 176, 63 -75.

AMA Style

A. Khosravi, R.N.N. Koury, L. Machado, Juan Jose Garcia Pabon. Prediction of hourly solar radiation in Abu Musa Island using machine learning algorithms. Journal of Cleaner Production. 2018; 176 ():63-75.

Chicago/Turabian Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. 2018. "Prediction of hourly solar radiation in Abu Musa Island using machine learning algorithms." Journal of Cleaner Production 176, no. : 63-75.

Journal article
Published: 01 February 2018 in Sustainable Energy Technologies and Assessments
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ACS Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. Prediction of wind speed and wind direction using artificial neural network, support vector regression and adaptive neuro-fuzzy inference system. Sustainable Energy Technologies and Assessments 2018, 25, 146 -160.

AMA Style

A. Khosravi, R.N.N. Koury, L. Machado, Juan Jose Garcia Pabon. Prediction of wind speed and wind direction using artificial neural network, support vector regression and adaptive neuro-fuzzy inference system. Sustainable Energy Technologies and Assessments. 2018; 25 ():146-160.

Chicago/Turabian Style

A. Khosravi; R.N.N. Koury; L. Machado; Juan Jose Garcia Pabon. 2018. "Prediction of wind speed and wind direction using artificial neural network, support vector regression and adaptive neuro-fuzzy inference system." Sustainable Energy Technologies and Assessments 25, no. : 146-160.