| 1. |
- Zendehboudi, A., et al.
(författare)
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Modeling and multi-objective optimization of an R450A vapor compression refrigeration system
- 2019
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Ingår i: International journal of refrigeration. - : Elsevier. - 0140-7007 .- 1879-2081. ; 100, s. 141-155
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of this work is to comprehensively investigate R450A behavior in refrigeration systems and subsequently optimize the main operating variables for the first time to reach the maximum performance. For this purpose, a hybrid multi-objective optimization model coupling response surface method and non-dominated sorted genetic algorithm II is established. The regression analysis results reveal a good agreement of experimental data samples with the quadratic polynomial models with a coefficient of determination exceeding 0.97. The optimum results for the first scenario indicate that the reduction in the motor-compressor electrical power consumption and discharge temperature is 18.39% and 53.51%, respectively, and percentage of growth in the refrigerant mass flow rate is 215.57% when the middle evaporator temperature, middle condenser temperature, superheating degree, and subcooling degree change from −14.95 °C to 8.71°C, 31.28 °C to 24.50°C, 13.12 K to 10.49 K, and 15.65 K to 15.66 K, respectively.
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| 2. |
- Belman-Flores, J. M., et al.
(författare)
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Experimental study of R1234yf as a drop-in replacement for R134a in a domestic refrigerator
- 2017
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Ingår i: International journal of refrigeration. - : ELSEVIER SCI LTD. - 0140-7007 .- 1879-2081. ; 81, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an experimental study for three identical domestic refrigerators using R1234yf as a drop-in replacement for R134a. An alternative methodology was proposed to estimate the optimal mass charge for R1234yf; with the use of such methodology, new evidences were sought on the thermal behavior of the refrigerator compartments as well as at the heat exchangers. Additionally, energy performance for both refrigerants was measured, and, finally, a TEWI analysis was conducted. For the type of refrigerator evaluated, results showed that R1234yf presented an average (for the 3 refrigerators) of 0.4 degrees C for the fresh food compartment, and 1.2 degrees C for the freezer, among different charges with respect to R134a. The optimal charge for R1234yf was 92.2 g, which is about 7.8% lower than the one for R134a, which represents a small increase of 4% in energy consumption in comparison to R134a. Finally, the TEWI analysis for the R1234yf was 1.07% higher than the R134a.
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| 3. |
- Belman-Flores, J. M., et al.
(författare)
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Using ANNs to approach to the energy performance for a small refrigeration system working with R134a and two alternative lower GWP mixtures
- 2017
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Ingår i: Applied Thermal Engineering. - : Elsevier Ltd. - 1359-4311 .- 1873-5606. ; 127, s. 996-1004
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an artificial neural network application to model a small refrigeration system is presented. The main objective of this study is an energy comparison of three refrigerants: R134a, R450A and R513A. The application of the artificial neural network was designed to model individually three typical energy parameters: the cooling capacity, the power consumption and the coefficient of performance, as a function of the evaporating temperature and the condensing temperature. Each model was validated using a technique called cross-validation, producing minimum relative errors of 0.15 for the cooling capacity and the coefficient of performance, while 0.05 for the power consumption. Based on the appropriate validation results, computer simulations were performed to build 3D color surfaces. After inspecting these 3D color surfaces, it was concluded that R450A presented a slightly lower cooling capacity than R134a, actually a 10% reduction in the cooling capacity was estimated. Similar results were observed for the power consumption, that is, R450A had about 10% less power consumption than the other two refrigerants. On the other hand, it was observed that R134a and R513A presented very similar energy behaviors. With respect the COP, it was concluded that all three refrigerants showed a very similar behavior. After the analysis performed with the artificial neural networks and the use of 3D surface color, it was concluded that R450A and R513A are appropriate refrigerants to replace R134a in the short term in applications at medium evaporating temperature.
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| 4. |
- Makhnatch, Pavel, et al.
(författare)
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Characteristics of R454C and R455A as R404A alternatives in commercial refrigeration
- 2018
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150241 ; , s. 547-553
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Konferensbidrag (refereegranskat)abstract
- R404A will be soon restricted from usage in commercial refrigeration in the European Union (EU) due to the requirements of the EU Regulation on fluorinated gases. Therefore, new refrigerant HFO/HFC mixtures are being developed to replace it. This paper explores the R454C and R455A as R404A alternatives and compares the characteristics that can lead their imposition in the refrigeration market. The characteristics studied are components and composition, current penetration in the market, security issues, global warming potential, energetic performance, material and lubricant compatibility and, finally, most likely applications.
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| 5. |
- Makhnatch, Pavel, et al.
(författare)
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Energy evaluation of drop-in replacements for R134a in cascade CO2/R134a refrigeration units
- 2018
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150265 ; , s. 1147-1153
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Konferensbidrag (refereegranskat)abstract
- The energy performance of CO2 standard booster systems is limited in countries with high ambient temperatures to replace R404A direct expansion architectures. Therefore, cascade refrigeration systems with CO2 in the low-pressure stage can be considered. Most of the conventional cascade refrigeration systems rely on using R134a, a high global warming potential (GWP) refrigerant, in the high pressure stage. However, R134a needs to be replaced by lower GWP refrigerants to meet the targets of current environmental agreements. This study investigates R450A and R513A refrigerants as drop-in replacements to R134a in R134a/CO2 cascade refrigeration units. The experimental energy performance results suggest that both R450A and R513A can substitute R134a in cascade systems. R513A provides comparable COP and cooling capacity values to R134a, whereas the cooling capacity and COP of R450A are lower than that of the baseline R134a.
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| 6. |
- Makhnatch, Pavel, et al.
(författare)
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Field measurements of AR404A low-temperature supermarket refrigeration system retrofitted with R449A
- 2018
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150241 ; , s. 468-474
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Konferensbidrag (refereegranskat)abstract
- Current international regulations set incentives to replace refrigerants with high global warming potential (GWP) values using environmentally friendly alternatives. This study presents the field measurements of an indirect commercial refrigeration system retrofitted with R449A, an alternative to R404A with a GWP value of 1282 (67% lower than that of R404A). The system has been operated at low evaporation temperature conditions(secondary refrigerant temperatures from -34 to -25°C). The results indicate that the cooling capacity of the retrofitted system was 1.3% lower than that of the reference R404A system on average, while the COP values are higher when using R449A (8.1% increase on average). The compressor discharge temperature increase is approximately 18.5 K. As a conclusion, R449A can be used as a replacement to R404A in indirect low-temperature supermarket refrigeration systems given that implications of its higher compressor discharge temperature, lower mass flow and difference in transport properties are taken into consideration.
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| 7. |
- Makhnatch, Pavel, et al.
(författare)
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Future refrigerant mix estimates as a result of the European Union regulation on fluorinated gases
- 2019
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150357 ; , s. 2318-2325
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Konferensbidrag (refereegranskat)abstract
- The requirements of the European Union (EU) regulation on fluorinated greenhouse gases has created an incentive to reduce their amount that can be placed on the EU market (including many commonly used refrigerants) to 21% of the baseline level. This study attempts to develop a methodology to predict the future refrigerant mix in refrigeration, air conditioning, and heat pumps that will be available to the EU customers by 2021 and 2030 years. The work is based on the relevant current statistical data, refrigerant distribution, and future technology acceptance and trends in refrigerants. The study presents a refrigerant demand grow scenario and provides a basis for closer market follow up in order to facilitate decision making for refrigeration industry stakeholders. The results of the study indicate that by 2021 will be difficult to accomplish the fluorinated gas quota but by 2030 the transition is possible. By that time, the natural refrigerants will dominate the market, and a small share of lower GWP refrigerants will be necessary for specific applications.
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| 8. |
- Mota-Babiloni, Adrian, et al.
(författare)
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Assessment of the utilization of equivalent warming impact metrics in refrigeration, air conditioning and heat pump systems
- 2020
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 129
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Forskningsöversikt (refereegranskat)abstract
- The refrigeration, air conditioning and heat pump (RACHP) industry is a significant contributor to the climate change through its associated direct and indirect greenhouse gas (GHG) emissions. Several policies and regulations are being approved to control the working fluids used in existing and future installations, but the equivalent environmental benefit is not clear. In works that analyze the operation of environmentally friendly refrigerants in different configurations, various metrics based on different assumptions have been used to calculate the CO2 equivalent reduction. This work reviews and analyses the environmental metrics used in RACHP systems and the assumptions proposed for their calculation, depending on the application, to promote their inclusion in future works. The peculiarities of each work are discussed together with an interpretation of their main considerations and simplifications. From the literature review and analysis, it is seen that despite the existence of guidelines for the environmental metrics calculation, considerations with notable differences for the same applications are still assumed, even in the case of the Life Cycle Climate Performance (LCCP) metric. Recommendations for the Total Equivalent Warming Impact (TEWI) metric application are provided.
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| 9. |
- Mota-Babiloni, A., et al.
(författare)
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Experimental exergy analysis of R513A to replace R134a in a small capacity refrigeration system
- 2018
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 162, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- The replacement of HFCs using lower GWP refrigerants in the coming years is a priority to reduce the predicted climate change. The exergy analysis of vapor compression systems can help to identify the feasibility of alternative fluids in existing installations and the potential to improve them. In this sense, this paper presents an exergy analysis of an experimental setup which operates with R134a and the alternative HFO/HFC mixture R513A. The evaporating temperature is ranges between −15 °C and 5 °C, while the condensing temperature is set at 30 °C and 35 °C. In this analysis, the highest amount of exergy destruction rate is obtained at the compressor, followed by the evaporator. The maximum exergy efficiencies are observed at the condenser and the thermostatic expansion device. Finally, the average global exergy efficiency of R513A when replaced R134a in this refrigeration experimental setup is 0.4% higher (absolute difference), and with respect to the components, there is only slight reduction in efficiency in the condenser using R513A. Therefore, the R513A replacement is acceptable according to the second law of thermodynamics.
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