| 1. |
- Badran, Bassam E., et al.
(författare)
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Theoretical Study of a Multilevel Heat Pump for Multi-Source Heating
- 2021
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Ingår i: 6Th Iir Conference On Thermophysical Properties And Transfer Processes Of Refrigerants (Tptpr2021). - : INT INST REFRIGERATION. ; , s. 243-250
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Konferensbidrag (refereegranskat)abstract
- Industry and other sectors are currently looking for solutions to decarbonize their processes, including heating, which is mainly based on fossil fuel boilers. Heat pumps can provide heating with higher performance based on their high coefficient of performance (COP). This work considers a multilevel heat pump (MTHP) for multi-source heating, based on a three-stage cascade in which excess heat in the condenser is used for external flows, that can be connected in series or parallel. Several available low GWP refrigerants have been considered, and a multi-parameter selection analysis has been carried out. For low, medium, and high-temperature stages, R1243zf, R-1224yd(Z), and R-1233zd(E) are the best refrigerants, respectively, selected. This system is able to operate between 0 and 160 degrees C, with three heating levels at 60, 110, 160 degrees C (31.75, 21.59, and 29.92 kW, respectively) at a COP of 2.181. The total cooling capacity of the system is 45.08 kW and the total heating capacity is 83.26 kW. The MTHP concept can provide a significant carbon footprint reduction compared to natural gas boilers used in European countries.
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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. |
- Ghanbarpour, Morteza, et al.
(författare)
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ANN Modeling to Analyze the R404A Replacement with the Low GWP Alternative R449A in an Indirect Supermarket Refrigeration System
- 2021
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 11:23
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Tidskriftsartikel (refereegranskat)abstract
- Artificial neural networks (ANNs) have been considered for assessing the potential of low GWP refrigerants in experimental setups. In this study, the capability of using R449A as a lower GWP replacement of R404A in different temperature levels of a supermarket refrigeration system is investigated through an ANN model trained using field measurements as input. The supermarket refrigeration was composed of two indirect expansion circuits operated at low and medium temperatures and external subcooling. The results predicted that R449A provides, on average, a higher 10% and 5% COP than R404A at low and medium temperatures, respectively. Moreover, the cooling capacity was almost similar with both refrigerants in both circuits. This study also revealed that the ANN model could be employed to accurately predict the energy performance of a commercial refrigeration system and provide a reasonable judgment about the capability of the alternative refrigerant to be retrofitted in the system. This is very important, especially when the measurement data comes from field measurements, in which values are obtained under variable operating conditions. Finally, the ANN results were used to compare the carbon footprint for both refrigerants. It was confirmed that this refrigerant replacement could reduce the emissions of supermarket refrigeration systems.
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| 4. |
- Ghanbarpour, Morteza, et al.
(författare)
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Energy, Exergy, and Environmental (3E) Analysis of Hydrocarbons as Low GWP Alternatives to R134a in Vapor Compression Refrigeration Configurations
- 2021
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:13, s. 6226-
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Tidskriftsartikel (refereegranskat)abstract
- The phase-down of hydrofluorocarbons and substitution with low global warming potential values are consequences of the awareness about the environmental impacts of greenhouse gases. This theoretical study evaluated the energy and exergy performances and the environmental impact of three vapor compression system configurations operating with the hydrocarbons R290, R600a, and R1270 as alternatives to R134a. The refrigeration cycle configurations investigated in this study include a single-stage cycle, a cycle equipped with an internal heat exchanger, and a two-stage cycle with vapor injection. According to the results, the alternative hydrocarbon refrigerants could provide comparable system performance to R134a. The analysis results also revealed that using an internal heat exchanger or a flash tank vapor injection could improve the system's efficiency while decreasing the heating capacity. The most efficient configuration was the two-stage refrigeration cycle with vapor injection, as revealed by the exergy analysis. The environmental impact analysis indicated that the utilization of environmentally-friendly refrigerants and improving the refrigeration system's efficiency could mitigate equivalent CO2 emissions significantly. The utilization of hydrocarbons reduced the carbon footprint by 50%, while a 1% to 8% reduction could be achieved using the internal heat exchanger and flash tank vapor injection.
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| 5. |
- Ghanbarpour, Morteza, et al.
(författare)
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Theoretical Global Warming Impact Evaluation of Medium and High Temperature Heat Pumps Using Low GWP Refrigerants
- 2021
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:15
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Tidskriftsartikel (refereegranskat)abstract
- This study provides a global warming impact analysis of environmentally friendly refrigerants used as replacements for R134a and R245fa. R290, R1234yf, R1234ze(E), R513A and R450A are considered as refrigerants to replace R134a in medium temperature applications. For R245fa, there are five alternative refrigerants, R1224yd(Z), R600, R1336mzz(Z), R1233zd(E) and R1234ze(Z), which are selected for high-temperature applications. The analysis is done considering the emission factors in Brazil, Sweden, Canada and Poland. In Sweden and Brazil, the total equivalent warming impact per heating capacity of R134a is higher than its alternative refrigerants in medium temperature application, although R134a exhibits a higher coefficient of performance than its alternatives. In high-temperature applications, R1336mzz(Z) has the lowest total equivalent warming impact per heating capacity due to its higher coefficient of performance than other tested refrigerants. The highest total equivalent warming impact per heating capacity belongs to R245fa in all countries except in Poland, where R600 exhibits a higher value due to its lower coefficient of performance and the relatively higher emission factor in Poland compared to other selected countries. These results revealed that in addition to the global warming potential, the emission factor associated with the sources of electricity generation has a crucial impact on indirect emissions.
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| 6. |
- Makhnatch, Pavel, et al.
(författare)
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Experimental study of R450A drop-in performance in an R134a small capacity refrigeration unit
- 2017
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Ingår i: International journal of refrigeration. - : Elsevier. - 0140-7007 .- 1879-2081. ; 84, s. 26-35
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Tidskriftsartikel (refereegranskat)abstract
- The Kigali's amendment to the Montreal Protocol has highlighted the hydrofluorocarbons (HFCs) phase out as a priority to reduce the future global Earth's mean temperature increase. R134a is the most abundant HFC in the atmosphere and therefore it must be substituted using environmentally benign alternatives. In the short term, blends of HFCs and hydrofluoroolefins can replace R134a. This paper experimentally evaluates R450A (GWP of 547), a non-flammable mixture of R1234ze(E) and R134a, in an R134a small capacity refrigeration system. The controlled experimental conditions cover evaporating temperatures from -15 to 12.5 °C and condensing temperature of 25, 30 and 35 °C (36 tests in total for each refrigerant). The experimental results showed that with only a thermostatic expansion valve adjustment the average R450A cooling capacity and COP are 9.9 and 2.9% lower than those measured using R134a. Besides, the observed compressor discharge temperature values of R450A are not greater than that of R134a.
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| 7. |
- Makhnatch, Pavel, et al.
(författare)
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R450A and R513A as lower GWP mixtures for high ambient temperature countries : Experimental comparison with R134a
- 2019
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Ingår i: Energy. - : Institutt for energiteknikk. - 0360-5442 .- 1873-6785. ; 166, s. 223-235
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Tidskriftsartikel (refereegranskat)abstract
- In recognition of the impact of the refrigeration sector on climate change, global commitments are achieved to replace hydrofluorocarbon substances with more planet-friendly alternatives. In this regard, countries with high ambient temperatures (HAT) face additional problems in identifying suitable alternatives due to the impact of such temperatures on energy performance in vapor compression systems. This paper presents an experimental analysis using R134a and two lower global warming potential (GWP) mixtures in a small capacity vapor compression refrigeration system for HAT environments. The range of evaporating and condensing conditions was selected to simulate a refrigeration system working at HAT conditions. The experimental operating results show that although R450A values are acceptable, R513A shows better adaptation to the refrigeration system in terms of pressure ratio, discharge temperature, and mass flow rate. Then, attending to experimental energetic results, R450A energy performance (quantified by COP) and cooling capacity are lower than R513A and R134a. TEWI analysis of a small refrigeration unit shows CO2 equivalent emission saving when using R450A in the different condensation conditions. However, taking into account the variation of cooling capacity, R513A system results in the lowest TEWI when normalizing per unit of delivered cooling capacity.
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| 8. |
- Makhnatch, Pavel, 1985-, et al.
(författare)
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Retrofit of lower GWP alternative R449A into an existing R404A indirect supermarket refrigeration system
- 2017
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Ingår i: International journal of refrigeration. - : Elsevier. - 0140-7007 .- 1879-2081. ; 76, s. 184-192
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Tidskriftsartikel (refereegranskat)abstract
- R404A is going to be phased out from most of the commercial refrigeration systems due to its high GWP value of 3943. R449A (GWP of 1282) has been proposed to replace R404A with only minor system modifications in supermarkets. This paper presents the measurements of a light retrofit replacement of R404A using R449A in a medium temperature indirect refrigeration system (secondary fluid temperature at the evaporator outlet between −9 and −4 °C). It has been demonstrated that with a slight expansion device adjustment and 4% increase of refrigerant charge, R449A can be used in this refrigeration system designed for R404A because of its suitable thermodynamic properties and acceptable maximum discharge temperature. At a secondary fluid temperature at condenser inlet of 30 °C, the COP of R449A nearly matches that of R404A (both were between 1.9 and 2.2), despite having approximately 13% lower cooling capacity. As a conclusion, attending to the GWP reduction and similar energy performance, it was demonstrated using the TEWI methodology that the use of the recently developed refrigerant R449A in these applications can reduce the total CO2equivalent emissions of an indirect supermarket refrigeration system designed for R404A refrigerant.
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| 9. |
- Makhnatch, Pavel, et al.
(författare)
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The effect of temperature glide on the performance of refrigeration systems
- 2017
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Ingår i: 5TH IIR INTERNATIONAL CONFERENCE ON THERMOPHYSICAL PROPERTIES AND TRANSFER PROCESSES OF REFRIGERANTS (TPTPR). ; , s. 333-340
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Konferensbidrag (refereegranskat)abstract
- Many currently used refrigerants are potent greenhouse gases and therefore need to be replaced with lower global warming potential (GWP) fluids. The list of the proposed replacements includes a significant amount of refrigerant mixtures that exhibit large temperature glides during the phase change. The use of such refrigerants will affect the temperature distribution in evaporator and condenser and thus impact a refrigerating system behavior. The current work analyses the effect of refrigerant glide on the performance of refrigeration systems. The discussion is supported with experimental observations of two different refrigeration systems at different operating conditions. The results suggest that refrigerant glide have significant effect on performance of systems through means of temperature glide matching, refrigerant composition variation and heat transfer coefficient degradation. This effect differs depending on the refrigeration system design, type of evaporator/condenser and thermodynamic properties of refrigerant. Attending to the experimental results of the study, it is concluded that the possible advantages of temperature glide are not utilized at the conditions of drop-in replacements.
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| 10. |
- Mateu-Royo, Carlos, et al.
(författare)
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High temperature heat pump integration into district heating network
- 2020
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- This study illustrates the potential of high temperature heat pumps (HTHPs) integration into district heating network (DHN) through a twofold approach, using DHN as a heat sink and source. It is used as a heat sink of HTHP that uses waste heat from the supermarket's refrigeration system as a heat source whereas it is used as a heat source to HTHP that provides heat to industrial applications. When the DHN acts as the heat sink, the integrated system provides a coefficient of performance (COP) of the waste heat recovery (WHR) system between 3.2 and 5.4, reducing the operating costs between 50% and 100% with an average price ratio of 2.25 compared with the standard CO2 refrigeration system. If the DHN is the heat source, the integrated system provides a COP from 2.8 to 5.7 for a heat sink of 110 degrees C. The alternative low-GWP refrigerants assessment illustrates that HC-290, HFO-1234ze(E) and HFO-1234yf were considered the ideal candidates to replace the HFC-134a, whereas HCFO-1233zd(E) and HCFO-1224yd(Z) were the most promising low-GWP refrigerants to replace HFC-245fa. Finally, the environmental results showed that the utilisation of the DHN as the heat sink in the integrated system solution produces about 60% lower equivalent CO2 emissions than the DHN generation mix. Moreover, using DHN as the heat source, the equivalent CO2 emissions can be reduced up to 98% in Sweden compared to conventional natural gas boilers. Hence, the combination of HTHPs and the DHN represents a step forward in the mitigation of climate change through the utilisation of sustainable energy conversion technologies.
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