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Project Goal: https://www.linkedin.com/in/eco2-rapject-project-557744191/
Current Stage: Ongoing
Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical CO2 air conditioning units are perceived to be eco-friendly and future-proof solutions to achieving such a target. However, in order to have highly efficient air conditioning systems, the CO2 charge needs to be optimized. In this paper the energy and exergy-based analyses were performed to investigate the effect of normalized refrigerant charge on the system performance by using a test rig of a transcritical CO2 air conditioning unit for an 8 m electric bus. Results showed that the normalized refrigerant charge range of 0.248~0.336 was recommended in order to ensure the maximum coefficient of performance (COP). In addition, in sufficient charge conditions, the optimal COP, cooling capacity and exergy efficiency were 1.716, 18.97 kW and 29.79%, respectively, under the standard refrigeration condition of 35 °C/27 °C. As the ambient temperature rose from 35 °C to 40 °C, the COP, cooling capacity and exergy efficiency decreased by 16.03%, 10.90% and 12.22%, respectively. Furthermore, the exergy efficiency was found not to be sensitive to slightly insufficient charge, whereas overcharge was observed to be even beneficial to exergy efficiency under the condition of ensuring the maximum COP. In addition, insufficient refrigerant charging seriously affected the irreversible losses in the indoor and outdoor heat exchangers, whereas slight overcharge had little effect on the component exergy efficiency. Finally, the need to improve the CO2 compressor efficiency to enhance the system performance was revealed.
Haidan Wang; Shengbo Li; Yulong Song; Xiang Yin; Feng Cao; Paride Gullo. Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical CO2 Electric Bus Air Conditioning System. Applied Sciences 2021, 11, 5614 .
AMA StyleHaidan Wang, Shengbo Li, Yulong Song, Xiang Yin, Feng Cao, Paride Gullo. Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical CO2 Electric Bus Air Conditioning System. Applied Sciences. 2021; 11 (12):5614.
Chicago/Turabian StyleHaidan Wang; Shengbo Li; Yulong Song; Xiang Yin; Feng Cao; Paride Gullo. 2021. "Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical CO2 Electric Bus Air Conditioning System." Applied Sciences 11, no. 12: 5614.
The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the gas cooler on the cycle parameters and system performance, a novel method to evaluate the optimal air flow rate was proposed. In addition, the effect of the gas cooler air volume flow rate on the key performance parameters of the system (e.g., optimal discharge pressure) was explored. Finally, the coupling effects of the compressor speed, ambient temperature and optimal air flow rate on the system performance was also exhaustively assessed. It was found that as the discharge temperature, the CO2 temperature at the gas cooler outlet and the discharge pressure did not vary more than ±2%, the corresponding gas cooler air volume flow rate was optimal. For the single-row and dual-process microchannel evaporator used in this work, the recommended value of the optimal gas cooler air volume flow rate was 2500 m3·h−1. The results could provide reference for the fan speed design of electric vehicle CO2 air conditioning systems, especially for the performance under idling model.
Anci Wang; Jianmin Fang; Xiang Yin; Yulong Song; Feng Cao; Paride Gullo. Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System. Applied Sciences 2021, 11, 4855 .
AMA StyleAnci Wang, Jianmin Fang, Xiang Yin, Yulong Song, Feng Cao, Paride Gullo. Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System. Applied Sciences. 2021; 11 (11):4855.
Chicago/Turabian StyleAnci Wang; Jianmin Fang; Xiang Yin; Yulong Song; Feng Cao; Paride Gullo. 2021. "Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System." Applied Sciences 11, no. 11: 4855.
The cooling industry involves various essential applications, such as food preservation, medicine storage and air conditioning. However, its significant direct and indirect contribution to global warming is bound to increase in years to come, leading to the need for highly efficient cooling units using eco-friendly working fluids. Consequently, carbon dioxide (R744) is achieving resounding success as a refrigerant for various medium- and large-capacity applications, as some of the available expansion work is recovered with the aid of two-phase ejectors. However, its adoption is being limited for small-capacity solutions (e.g. condensing units) due to the current lack of a suitable flow modulation technique for two-phase ejectors installed in these units. Therefore, the goal of this work is to bridge this knowledge gap by formulating and experimentally proving an innovative flow control mechanism for two-phase ejectors, being based on the pulse-width modulation (PWM) of the refrigerant flow through the ejector. All the experimental evaluations were carried out at the compressor speed of 50 Hz, water temperature at the gas cooler inlet of 35 °C and R744 evaporating temperature of about −5 °C. The first experimental data revealed that the high pressure can be controlled appropriately as well as varied from about 87 bar to 112 bar, demonstrating the effectiveness of the proposed technique. In addition, the effect of the muffler volume as well as the PWM period on the ejector and system performance were investigated. It was found that the influence of both the muffler volume and the PWM period was not significant. Compared to the solution employing the passive ejector (i.e. without flow modulation technique), the unit with the PWM ejector presented enhancements in coefficient of performance (COP) by more than 5% at the optimum operation conditions. It is worth mentioning that its today’s available competitors, i.e. needle-based ejector and vortex-based ejector, feature COP enhancements by 2%–4% as contrasted with the passive ejector. As benchmarked to the standard unit (i.e. with flash gas by-pass valve and without ejector), the PWM ejector could improve the COP by more than 10% at the optimal running conditions. Also, the results obtained suggest that at present the proposed solution should operate with a PWM period of 2 s and no mufflers. Finally, the PWM ejector is characterized by low cost, simplicity, low vulnerability to clogging and no practical size or application constraints.
Paride Gullo; Michael Birkelund; Ekaterini E. Kriezi; Martin Ryhl Kærn. Novel flow modulation method for R744 two-phase ejectors – Proof of concept, optimization and first experimental results. Energy Conversion and Management 2021, 237, 114082 .
AMA StyleParide Gullo, Michael Birkelund, Ekaterini E. Kriezi, Martin Ryhl Kærn. Novel flow modulation method for R744 two-phase ejectors – Proof of concept, optimization and first experimental results. Energy Conversion and Management. 2021; 237 ():114082.
Chicago/Turabian StyleParide Gullo; Michael Birkelund; Ekaterini E. Kriezi; Martin Ryhl Kærn. 2021. "Novel flow modulation method for R744 two-phase ejectors – Proof of concept, optimization and first experimental results." Energy Conversion and Management 237, no. : 114082.
Tourism, and thereby hotels, play a crucial role in the European economy. The hotel sector features high energy consumption, which greatly contributes to the global warming effect. Thus, there is a need to investigate environmentally friendly technologies that have the potential to reduce energy usage within this sector. Information regarding the current status of the energy consumption in hotels is essential. Therefore, a study of 140 hotels in Norway and Sweden is presented in this paper to identify successful and sustainable measures to reduce energy consumption and related emissions. The energy use, available energy sources and thermal systems in the hotels are studied over a five-year period to identify consumption trends. The results reveal that 70 % of the hotels have a mean annual energy consumption between 150 and 250 kWh/m2. A shift towards sustainable energy sources is observed in the hotels from 2015 to 2019, where application and overall consumption of district heating and cooling have increased, while electrical energy consumption has been reduced. District heating is the most prominent source of heating and is applied as the primary heat source in 70 % of the hotels. The specific energy consumption for the group hotels that apply district heating is 218.9 kWh/m2/year, which is nearly 25 % higher than the specific energy consumption of the 9 % of hotels that apply heat pump solutions as a primary heat source. Thus, there is a potential to reduce the specific energy consumption in hotels. Two integrated transcritical carbon dioxide (CO2) heat pumps were investigated as a sustainable measure to reduce energy consumption. The results reveal that a reduction of thermal energy consumption of approximately 60 % can be achieved.
S. Smitt; I. Tolstorebrov; P. Gullo; A. Pardiñas; A. Hafner. Energy use and retrofitting potential of heat pumps in cold climate hotels. Journal of Cleaner Production 2021, 298, 126799 .
AMA StyleS. Smitt, I. Tolstorebrov, P. Gullo, A. Pardiñas, A. Hafner. Energy use and retrofitting potential of heat pumps in cold climate hotels. Journal of Cleaner Production. 2021; 298 ():126799.
Chicago/Turabian StyleS. Smitt; I. Tolstorebrov; P. Gullo; A. Pardiñas; A. Hafner. 2021. "Energy use and retrofitting potential of heat pumps in cold climate hotels." Journal of Cleaner Production 298, no. : 126799.
Climate change mitigation actions have led transcritical R744 refrigeration systems to take center stage in supermarket applications worldwide. Various measures aimed at making these solutions highly performing in any climate context, in fact, have been developed in the last few years. However, their benefits have been evaluated and quantified almost uniquely with the aid of conventional tools, e.g. energy and environmental assessments. Therefore, in this work the most power thermodynamic tool for such a purpose, i.e. the advanced exergy analysis, was applied to the state-of-the-art transcritical R744 supermarket refrigeration systems for the first time ever. Three advanced solutions, namely R744 unit with parallel compression and a R744 system using parallel compression and overfed evaporators with and without two-phase ejectors, were selected in addition to two baselines, being conventional and improved basic R744 units. The investigation was based on the outdoor temperature of 40 °C and operating conditions derived from field measurements. The results obtained suggested that the conventional basic R744 unit features total irreversibilities of 194.49 kW and total unavoidable irreversibilities of 81.96 kW, whereas total irreversibilities and total unavoidable irreversibilities respectively amounted to 168.80 kW and 81.44 kW for the improved basic R744 system. As parallel compression was considered, potential reductions from 143.30 kW down to 67.20 kW, i.e. approximately 18% lower in comparison with the conventional basic unit and the improved basic system, were assed. The use of overfed evaporators was found to lead to potential decrements in total irreversibilities down to 63.79 kW, which were around 5% lower in comparison with parallel compression and 22% lower than with the conventional basic unit and the improved basic system. In addition, the outcomes associated with advanced exergy analysis implementation revealed the need to adopt two-phase ejectors as well as more efficient parallel compressors. The first measure would permit decreasing the total irreversibilities potentially from 115.04 kW down to 44.35 kW, resulting in decrement by about 46% compared to conventional and improved basic R744 systems, 34% in relation to the unit with parallel compressors and 30.5% over the solution with parallel compressors and overfed evaporators. Also, if 10% more efficient parallel compressors had been available, total irreversibilities, total unavoidable irreversibilities and total avoidable irreversibilities of the solution with two-phase ejectors would have been further reducible by 9.3%, 2.6% and 13.5%, respectively. It could be concluded that ejector-based transcritical R744 supermarket refrigeration systems possibly with high performing parallel compressors are capable of providing great thermodynamic performance at high sink temperatures. In addition, the vapour ejectors were found to be responsible for 22.9% of the total avoidable inefficiencies. These irreversibilities could be decremented by almost uniquely enhancing the performance of the ejectors themselves. However, unlike the results derived from conventional energy and environmental analyses, the outcomes of the advanced exergy methodology did not reveal a significant contribution on the part of the overfed evaporators to the thermodynamic performance enhancement of transcritical R744 supermarket refrigerating plants.
Paride Gullo. Impact and quantification of various individual thermodynamic improvements for transcritical R744 supermarket refrigeration systems based on advanced exergy analysis. Energy Conversion and Management 2020, 229, 113684 .
AMA StyleParide Gullo. Impact and quantification of various individual thermodynamic improvements for transcritical R744 supermarket refrigeration systems based on advanced exergy analysis. Energy Conversion and Management. 2020; 229 ():113684.
Chicago/Turabian StyleParide Gullo. 2020. "Impact and quantification of various individual thermodynamic improvements for transcritical R744 supermarket refrigeration systems based on advanced exergy analysis." Energy Conversion and Management 229, no. : 113684.
In the case of R744 refrigeration technology, the system equipped with a two-phase ejector is one of the most efficient refrigeration systems, allowing utilisation of an R744-based unit in hot and tropical climates. However, the experimental analyses of the ejector-based system have only been performed for system performance evaluation, mapping the performance of ejectors or validation of the ejector numerical simulation. Therefore, the main goal/scope of this paper is to enhance the experimental knowledge of the state-of-the-art R744 vapour compression rack equipped with an efficient two-phase ejector, the relationship between the ejector and other components, and the influence of unsteady system work on the ejector performance and cooling demand. The test campaign was carried out on the R744 ejector-based test rig with a cooling capacity of 50 kW, high-side pressures from 60 bar to 100 bar and temperatures from 15°C to 40°C. The experimental analysis was conducted for three different system operating conditions, namely, short-term, long-term, and unsteady-state conditions, for refrigeration and air-conditioning applications. Utilisation of the ejector influenced the system instability, especially at the internal heat exchanger control. In addition, the low-pressure lift below 4 bar allowed the most efficient control strategy of the cooling demand for the operation below the critical point. For the transcritical unsteady operation, the most efficient operation was obtained for the defined pressure lift of 6 bar.
Michal Haida; Michal Palacz; Jakub Bodys; Jacek Smolka; Paride Gullo; Andrzej J. Nowak. An experimental investigation of performance and instabilities of the R744 vapour compression rack equipped with a two-phase ejector based on short-term, long-term and unsteady operations. Applied Thermal Engineering 2020, 185, 116353 .
AMA StyleMichal Haida, Michal Palacz, Jakub Bodys, Jacek Smolka, Paride Gullo, Andrzej J. Nowak. An experimental investigation of performance and instabilities of the R744 vapour compression rack equipped with a two-phase ejector based on short-term, long-term and unsteady operations. Applied Thermal Engineering. 2020; 185 ():116353.
Chicago/Turabian StyleMichal Haida; Michal Palacz; Jakub Bodys; Jacek Smolka; Paride Gullo; Andrzej J. Nowak. 2020. "An experimental investigation of performance and instabilities of the R744 vapour compression rack equipped with a two-phase ejector based on short-term, long-term and unsteady operations." Applied Thermal Engineering 185, no. : 116353.
Ejector-equipped vapor-compression systems for refrigeration and cooling, relying solely on CO2 (R744) as a natural working fluid, are perceived to be an eco-friendly and highly efficient solution for many applications. However, the complexity of two-phase ejector flows makes it very challenging to find realiable and efficient ejector designs. Improved design methods are necessary in order to achieve higher performance in R744 units compared to the traditional compressor-based systems with refrigerants that put a high strain on the environment. Consequently, the development of advanced models and tools for an accurate design of the R744 ejectors has been a highly prioritized research topic. To the best of the authors’ knowledge, the current status of R744 ejector models and their limitations has not been thoroughly evaluated yet. To summarise the current state of the art and knowledge gaps, this work presents an exhaustive overview of the available numerical models applied to R744 two-phase ejectors, i.e. multiphase flow modeling, turbulence aspects, numerical solution methods, applications of models, to further encourage the adoption of R744 vapor-compression solutions. Finally, a thorough discussion of different focus points for future research as well as the main challenges in the field is presented.
Knut Emil Ringstad; Yosr Allouche; Paride Gullo; Åsmund Ervik; Krzysztof Banasiak; Armin Hafner. A detailed review on CO2 two-phase ejector flow modeling. Thermal Science and Engineering Progress 2020, 20, 100647 .
AMA StyleKnut Emil Ringstad, Yosr Allouche, Paride Gullo, Åsmund Ervik, Krzysztof Banasiak, Armin Hafner. A detailed review on CO2 two-phase ejector flow modeling. Thermal Science and Engineering Progress. 2020; 20 ():100647.
Chicago/Turabian StyleKnut Emil Ringstad; Yosr Allouche; Paride Gullo; Åsmund Ervik; Krzysztof Banasiak; Armin Hafner. 2020. "A detailed review on CO2 two-phase ejector flow modeling." Thermal Science and Engineering Progress 20, no. : 100647.
The adoption of highly efficient vapour-compression heating, ventilation, air conditioning and refrigeration (HVAC&R) systems is compulsory to achieve a low-carbon society. Expansion work recovery using a two-phase ejector is widely recognized as one of the most promising measures to improve the energy efficiency of HVAC&R units. This holds true for all operation conditions provided that an effective capacity control technique is implemented. In this work a thorough critical review on the current status of the presently available capacity control strategies for two-phase ejectors was carried out. In addition, their pros and cons as well as the comparison of their performance were reported. It was concluded that two-phase ejectors can be properly capacity controlled in large- and medium-scale vapour-compression units. However, a suitable capacity control mechanism for small-scale vapour-compression solutions still requires a major breakthrough and is being intensively discussed among experts in the field.
Paride Gullo; Martin Ryhl Kærn; Michal Haida; Jacek Smolka; Stefan Elbel. A review on current status of capacity control techniques for two-phase ejectors. International Journal of Refrigeration 2020, 119, 64 -79.
AMA StyleParide Gullo, Martin Ryhl Kærn, Michal Haida, Jacek Smolka, Stefan Elbel. A review on current status of capacity control techniques for two-phase ejectors. International Journal of Refrigeration. 2020; 119 ():64-79.
Chicago/Turabian StyleParide Gullo; Martin Ryhl Kærn; Michal Haida; Jacek Smolka; Stefan Elbel. 2020. "A review on current status of capacity control techniques for two-phase ejectors." International Journal of Refrigeration 119, no. : 64-79.
The adoption of highly efficient vapour-compression refrigeration, air conditioning and heat pump (RACHP) systems is compulsory to achieve a low-carbon society. Expansion work recovery using a two-phase ejector is widely recognized as one of the most promising measures to improve the energy efficiency of RACHP units. This holds true for all operation conditions provided that an effective capacity control technique is implemented. In this work a thorough critical review on the current status of the presently available capacity control techniques for two-phase ejectors was carried out. In addition, their pros and cons as well as the comparison of their performance were reported. It was concluded that two-phase ejectors can be properly capacity controlled in large- and medium-scale vapour-compression units. However, a suitable capacity control mechanism for small-scale vapour-compression solutions still requires a major breakthrough and is being intensively discussed among experts in the field.
Paride Gullo; Martin Ryhl Kærn; Michal Haida; Jacek Smolka; Stefan Elbel. A review on current status of capacity control techniques for two-phase ejectors. 2020, 1 .
AMA StyleParide Gullo, Martin Ryhl Kærn, Michal Haida, Jacek Smolka, Stefan Elbel. A review on current status of capacity control techniques for two-phase ejectors. . 2020; ():1.
Chicago/Turabian StyleParide Gullo; Martin Ryhl Kærn; Michal Haida; Jacek Smolka; Stefan Elbel. 2020. "A review on current status of capacity control techniques for two-phase ejectors." , no. : 1.
Heat pump technologies for space heating can contribute to substantial economic, environmental and energy saving benefits. However, their performance is generally evaluated through energy-based methods. The distinguish feature of the exergy-based approaches is that, unlike to the energy-based ones, they are more powerful and convenient tools for developing, evaluating, understanding and improving energy conversion systems without the need of additional analysis and iterations. Exergy-based estimation (i.e. exergy, exergeconomic and exergoenvironmental analysis) has been applied to an air-source R134a heat pump unit for space heating, being this solution widely employed worldwide. According to the results obtained 63% and 20% of the avoidable exergy destruction within the heat pump belongs to inefficiencies within the evaporator and the condenser respectively. For the investigated heat pump the biggest parts of the avoidable cost associated with investment expenditures and exergy destruction belong to the compressor (56%) and the evaporator (35%). For the compressor this is caused mostly by capital investment and for the evaporator - mostly by its thermodynamic inefficiency. About 70% of the total avoidable environmental impact associated with construction and exergy destruction belongs to the evaporator and can be decreased mostly by improving thermodynamic efficiency of this component. For simultaneous improvement of thermodynamic, economic and environmental performance of the investigated solution the irreversibilities occurring in the evaporator and in the condenser has to be decreased. In addition, it is found that, to achieve such a target, reducing the temperature differences through both heat exchangers is a more suitable measure compared to the replacement of the existing emission heating system. The derived exergy-based conclusions are confirmed with objective functions based on a set of energy, economic and environmental criteria. Compared with the initial case the improved solution provides the reduced value of annual exergy destruction by 31%. The annual cost of exergy of the product of the improved system is also decreased by several percent. The annual environmental impact associated with the product of the system is decreased by 9.5%.
Volodymyr Voloshchuk; Paride Gullo; Volodymyr Sereda. Advanced exergy-based performance enhancement of heat pump space heating system. Energy 2020, 205, 117953 .
AMA StyleVolodymyr Voloshchuk, Paride Gullo, Volodymyr Sereda. Advanced exergy-based performance enhancement of heat pump space heating system. Energy. 2020; 205 ():117953.
Chicago/Turabian StyleVolodymyr Voloshchuk; Paride Gullo; Volodymyr Sereda. 2020. "Advanced exergy-based performance enhancement of heat pump space heating system." Energy 205, no. : 117953.
The work demonstrates the results of application of the detailed advanced exergetic analysis to air-source, watersource and wastewater-source heat pumps providing space heating in the built environment. Cumulative values based on seasonal exergy destruction are used for deriving conclusions. It is shown that in the specified conditions of the investigated systems priorities for improving should be given to heat exchangers.
Volodymyr Voloshchuk; Paride Gullo. Exergy-based Investigation of Various Heat Pumps for Enhancement of Their Thermodynamic Efficiency. Modeling, Control and Information Technologies 2019, 168 -168.
AMA StyleVolodymyr Voloshchuk, Paride Gullo. Exergy-based Investigation of Various Heat Pumps for Enhancement of Their Thermodynamic Efficiency. Modeling, Control and Information Technologies. 2019; (3):168-168.
Chicago/Turabian StyleVolodymyr Voloshchuk; Paride Gullo. 2019. "Exergy-based Investigation of Various Heat Pumps for Enhancement of Their Thermodynamic Efficiency." Modeling, Control and Information Technologies , no. 3: 168-168.
The regulatory pressures on environmentally deleterious refrigerants have been growing more intense, prompting CO2 to draw ever-widening attraction as the sole working fluid (R744) in supermarket applications. Direct space heating and cooling is considered as one of the most appealing techniques to promote the diffusion of “CO2 only” systems in warm and hot climates. However, to the best of the author's knowledge, the energy and environmental benefits related to its adoption have not been estimated yet. The results of this work revealed that “CO2 only” units implementing direct space heating and cooling offer an annual energy saving by up to 33.3% as well as a reduction in carbon footprint by up to 89.5% compared to the systems using hydrofluorocarbons (HFCs) in high ambient temperature countries. It could be concluded that direct space heating and cooling is a very good prospect to lead to a HFC-free future of supermarkets, even in hot climates.
Paride Gullo. Innovative fully integrated transcritical R744 refrigeration systems for a HFC-free future of supermarkets in warm and hot climates. International Journal of Refrigeration 2019, 108, 283 -310.
AMA StyleParide Gullo. Innovative fully integrated transcritical R744 refrigeration systems for a HFC-free future of supermarkets in warm and hot climates. International Journal of Refrigeration. 2019; 108 ():283-310.
Chicago/Turabian StyleParide Gullo. 2019. "Innovative fully integrated transcritical R744 refrigeration systems for a HFC-free future of supermarkets in warm and hot climates." International Journal of Refrigeration 108, no. : 283-310.
The adoption of the EU F-Gas Regulation 517/2014 and the resulting development of the multi-ejector concept have led carbon dioxide to take center stage as the sole refrigerant (R744) in several applications. Therefore, a knock-on effect on the number of supermarkets relying on “CO2 only” refrigeration systems has been experienced. Additionally, a global consensus of commercial multi-ejector based R744 units is also intensifying as a consequence of both the promising results obtained and the other measures in force for environment preservation. Furthermore, the multi-ejector concept is expected to offer significant energy savings in other high energy-demanding buildings (e.g., hotels, gyms, spas) as well, even in warm climates. In this investigation, the evolution of R744 ejector supported parallel vapor compression system layouts for food retail applications was summed up. Furthermore, their technological aspects, the results related to the main theoretical assessments and some relevant field/laboratory measurements were summarized. Also, the experience gained in the adoption of the multi-ejector concept in transcritical R744 vapor-compression units aimed at other energy intensive applications was presented. Finally, the persistent barriers needing to be overcome as well as the required future work were brought to light.
Paride Gullo; Armin Hafner; Krzysztof Banasiak; Silvia Minetto; Ekaterini E. Kriezi. Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments. Energies 2019, 12, 406 .
AMA StyleParide Gullo, Armin Hafner, Krzysztof Banasiak, Silvia Minetto, Ekaterini E. Kriezi. Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments. Energies. 2019; 12 (3):406.
Chicago/Turabian StyleParide Gullo; Armin Hafner; Krzysztof Banasiak; Silvia Minetto; Ekaterini E. Kriezi. 2019. "Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments." Energies 12, no. 3: 406.
After the recent renewed interest in CO2 as the refrigerant (R744) for the food retail industry, many researchers have focused on the performance enhancement of the basic transcritical R744 supermarket refrigeration unit in warm climates. This task is generally fulfilled with the aid of energy-based methods. However, the implementation of an advanced exergy analysis is mandatory to properly evaluate the best strategies needing to be implemented to achieve the greatest thermodynamic performance improvements. Such an assessment, in fact, is widely recognized as the most powerful thermodynamic tool for this purpose. In this work, the advanced exergy analysis was applied to a conventional R744 booster supermarket refrigerating system at the outdoor temperature of 40 °C. The results obtained suggested the adoption of a more sophisticated layout, i.e., the one outfitted with the multi-ejector block. It was found that the multi-ejector supported CO2 system can reduce the total exergy destruction rate by about 39% in comparison with the conventional booster unit. Additionally, the total avoidable exergy destruction rate was decreased from 67.60 to 45.57 kW as well as the total unavoidable exergy destruction rate was brought from 42.67 down to 21.91 kW.
Paride Gullo; Armin Hafner; Krzysztof Banasiak. Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis. Energies 2019, 12, 354 .
AMA StyleParide Gullo, Armin Hafner, Krzysztof Banasiak. Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis. Energies. 2019; 12 (3):354.
Chicago/Turabian StyleParide Gullo; Armin Hafner; Krzysztof Banasiak. 2019. "Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis." Energies 12, no. 3: 354.
In this work the thermodynamic performance of a transcritical R744 booster supermarket refrigeration system equipped with R290 dedicated mechanical subcooling (DMS) was exhaustively investigated with the aid of the advanced exergy analysis. The outcomes obtained suggested that improvement priority needs to be addressed to the manufacturing of more efficient high-stage (HS) compressors, followed by the enhancement of the gas cooler/condenser (GC), of the medium-temperature (MT) evaporators, of the R290 compressor, and of the low-temperature (LT) evaporators. These conclusions were different from those drawn by the application of the conventional exergy assessment. Additionally, it was found that GC can be enhanced mainly by reducing the irreversibilities owing to the simultaneous interaction among the components. The R290 compressor would also have significantly benefitted from the adoption of such measures, as half of its avoidable irreversibilities were exogenous. Unlike the aforementioned components, all the evaporators were improvable uniquely by decreasing their temperature difference. Finally, the approach temperature of GC and the outdoor temperature were found to have a noteworthy impact on the avoidable irreversibilities of the investigated solution.
Paride Gullo. Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling. Energies 2018, 11, 3058 .
AMA StyleParide Gullo. Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling. Energies. 2018; 11 (11):3058.
Chicago/Turabian StyleParide Gullo. 2018. "Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling." Energies 11, no. 11: 3058.
The ever-stricter regulations put into effect worldwide to significantly decrease the considerable carbon footprint of commercial refrigeration sector have forced the transition to eco-friendlier working fluids (e.g. CO2, R290, R1234ze(E), R450A, R513A). However, the identification of the most suitable long-term refrigerant is still today's major challenge for supermarkets located in high ambient temperature countries, especially as their air conditioning (AC) need is considered. The results of this theoretical study revealed that multi-ejector “CO2 only” systems can outperform R404A-, R290-, R1234ze(E)-, R134a-, R450A- and R513A-based solutions in an average-size supermarket located in various cities below the so-called “CO2 equator”. In fact, energy savings as well as reductions in environmental impact respectively up to 26.9% and 90.9% were estimated over conventional hydrofluorocarbon (HFC)-based solutions for the scenario including the AC demand. Also, the solution using multi-ejector block (in non-optimized operating conditions) enabled reducing the power input up to 50.3% over HFC-based units at outdoor temperatures from −10 °C to 5 °C. Finally, the study demonstrated that transcritical CO2 multi-ejector systems integrated with the AC unit allow potentially pushing the “CO2 equator” further South than Northern Africa.
Paride Gullo; Konstantinos M. Tsamos; Armin Hafner; Krzysztof Banasiak; Yunting T. Ge; Savvas A. Tassou. Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study. Energy 2018, 164, 236 -263.
AMA StyleParide Gullo, Konstantinos M. Tsamos, Armin Hafner, Krzysztof Banasiak, Yunting T. Ge, Savvas A. Tassou. Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study. Energy. 2018; 164 ():236-263.
Chicago/Turabian StyleParide Gullo; Konstantinos M. Tsamos; Armin Hafner; Krzysztof Banasiak; Yunting T. Ge; Savvas A. Tassou. 2018. "Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study." Energy 164, no. : 236-263.
Visible signs of climate change call for urgent actions on food retail industry, since such a sector is characterized by an abundant carbon footprint. Being CO2 (or R744) recognised across the world as the most promising working fluid for supermarket applications, commercial transcritical R744 refrigeration systems have emerged as leading hydrofluorocarbon (HFC)-free technologies. This study is intended to implement an in-depth review study covering the most important aspects related to the state-of-the-art pure R744 refrigeration plants for food retail applications, including the evolution of system architectures, some field measurements, the main available results from an energy, environmental and economic perspective as well as the indispensable future investigations. It could be concluded that, in spite of some persisting barriers which still prevent such technologies from a wider adoption, the usage of R744 as the only refrigerant in supermarkets is no longer open to dispute, even in warm locations.
Paride Gullo; Armin Hafner; Krzysztof Banasiak. Transcritical R744 refrigeration systems for supermarket applications: Current status and future perspectives. International Journal of Refrigeration 2018, 93, 269 -310.
AMA StyleParide Gullo, Armin Hafner, Krzysztof Banasiak. Transcritical R744 refrigeration systems for supermarket applications: Current status and future perspectives. International Journal of Refrigeration. 2018; 93 ():269-310.
Chicago/Turabian StyleParide Gullo; Armin Hafner; Krzysztof Banasiak. 2018. "Transcritical R744 refrigeration systems for supermarket applications: Current status and future perspectives." International Journal of Refrigeration 93, no. : 269-310.
Convective heat transfer of alumina/water nanofluid flow through flat plate PV/T panel in laminar flow has been investigated numerically in this study. Majority of previous studies, reported comparison in performance of nanofluid with that of basefluid, based on equal Reynolds number criterion. Hence, there is limited exploration of other comparison bases. A novel and prominent comparison basis, besides conventional equal Reynolds number, is equal pumping power and appears more practically oriented. Nanofluid, having particle dimension of 20 nm and inlet temperature of 293 K, is loaded with 1%, 4% and 6% of particle volume fraction with Reynolds number varying from 300 to 1800. Simulation results indicate average 25.2% improvement in heat transfer coefficient for nanofluid under equal Reynolds number comparison basis. While, under equal pumping power comparison criterion, the heat transfer coefficient for nanofluid is found to have average decrement up to 13.8%. Entropy generation for nanofluid reduces significantly, maximum up to 31%, under equal Reynolds number comparison criterion only. Alumina/water nanofluid in flat plate PV/T channel is found beneficial only under equal Reynolds number comparison basis.
Nilesh Purohit; Sanjeev Jakhar; Paride Gullo; Mani Sankar Dasgupta. Heat transfer and entropy generation analysis of alumina/water nanofluid in a flat plate PV/T collector under equal pumping power comparison criterion. Renewable Energy 2018, 120, 14 -22.
AMA StyleNilesh Purohit, Sanjeev Jakhar, Paride Gullo, Mani Sankar Dasgupta. Heat transfer and entropy generation analysis of alumina/water nanofluid in a flat plate PV/T collector under equal pumping power comparison criterion. Renewable Energy. 2018; 120 ():14-22.
Chicago/Turabian StyleNilesh Purohit; Sanjeev Jakhar; Paride Gullo; Mani Sankar Dasgupta. 2018. "Heat transfer and entropy generation analysis of alumina/water nanofluid in a flat plate PV/T collector under equal pumping power comparison criterion." Renewable Energy 120, no. : 14-22.
Supermarkets are currently one of the most vital service facilities, whose number of installations is ever-growing in both developed and developing countries. On the other hand, these applications feature a copious indirect contribution to the ongoing climate change, as well as a massive use of potent greenhouse gases. In an attempt to promote climate-friendlier technologies in commercial refrigeration sector, “CO 2 only” (transcritical CO 2 or pure CO 2 ) refrigeration systems have become the mainstream of new food retails worldwide. In particular, in the last few years parallel (or auxiliary) compression has taken root in food retails as a means to enhance the energy efficiency of pure CO 2 units. The thermodynamic performance of such a promising solution can be suitably assessed with the aid of the advanced exergy analysis. The results obtained at the design outdoor temperature of 40 °C showed that the main compressor has the highest priority of enhancement, whereas the high-pressure expansion valve needs to be replaced with a device for expansion work recovery. Also, close attention had to be paid to both the gas cooler and the auxiliary compressor. The former can be improved mainly by enhancing the other components, whereas the irreversibilities related to the latter can be decreased by improving both the compressor itself and the remaining components. Finally, the implemented sensitivity analysis revealed that the improvement in the efficiency of the main compressor should be seriously considered on the part of the manufacturers.
Paride Gullo; Armin Hafner. Thermodynamic Performance Assessment of a CO2 Supermarket Refrigeration System with Auxiliary Compression Economization by using Advanced Exergy Analysis. International Journal of Thermodynamics 2017, 20, 220 -227.
AMA StyleParide Gullo, Armin Hafner. Thermodynamic Performance Assessment of a CO2 Supermarket Refrigeration System with Auxiliary Compression Economization by using Advanced Exergy Analysis. International Journal of Thermodynamics. 2017; 20 (4):220-227.
Chicago/Turabian StyleParide Gullo; Armin Hafner. 2017. "Thermodynamic Performance Assessment of a CO2 Supermarket Refrigeration System with Auxiliary Compression Economization by using Advanced Exergy Analysis." International Journal of Thermodynamics 20, no. 4: 220-227.