Thermodynamic Analysis of a Multi-Ejector, CO2, Air-To-Water Heat Pump System

Boccardi, G.; Botticella, Francesco; Lillo, Gianluca; Mastrullo, R.; Mauro, A.W.; Trinchieri, R.

doi:10.1016/j.egypro.2016.11.107

Cited by 16 publications

(9 citation statements)

References 9 publications

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“…An exergy analysis has been performed for a CO 2 air-to-water heat pump using the multi ejector systems by Boccardi et al [23]. They confirmed that the throttling irreversibilities can be reduced to 46% by adopting the ejector system.…”

Section: Introductionmentioning

confidence: 91%

Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

2019

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In this study, the exergy analysis of a CO2 (R744) two-phase ejector was performed using a 1D model for both single and double choking conditions. The impact of the back pressure on the exergy destruction and exergy efficiencies was presented to evaluate the exergy performance under different working conditions. The results of two exergy performance criteria (transiting exergy efficiency and Grassmann exergy efficiency) were compared for three modes of an ejector functioning: Double choking, single choking and at the critical point. The behavior of three thermodynamic metrics: Exergy produced, exergy consumed and exergy destruction were evaluated. An important result concerning the ejector’s design was the presence of a maximum value of transiting exergy efficiency around the critical point. The impact of the gas cooler and evaporator pressure variations on the different types of exergy, the irreversibilities and the ejector global performance were investigated for a transcritical CO2 ejector system. It was also shown that the transiting exergy flow had an important effect on the exergy analysis of the system and the Grassmann exergy efficiency was not an appropriate criterion to evaluate a transcritical CO2 ejector performance.

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Section: Introductionmentioning

confidence: 91%

Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

2019

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“…The results obtained by Boccardi et al [75] suggested that the throttling losses of a R744 air-to-water heat pump unit can be decreased by 46% by adopting the multi-ejector concept over the investigated running modes. However, the improvement in overall exergy efficiency was found to be, at best, equal to 9% in comparison with the basic solution.…”

Section: Laboratory Experimental Assessmentsmentioning

confidence: 99%

“…Finally, it was found that it is needed to switch from an ejector configuration to another in order to maximize the performance with respect to the external temperature (Figure 29c). Boccardi et al [75,76] also evaluated ejector efficiencies below the ones available in the open literature. This was due to the fact that a multi-ejector module designed for refrigeration applications (i.e., high pressure lift and low mass entrainment ratio) was used.…”

Section: Laboratory Experimental Assessmentsmentioning

confidence: 99%

“…Singh et al [77] experimentally assessed the performance of a transcritical R744 heat pumping system equipped with multi-ejector block aimed at hot water production in the Indian climate context. The results showed that total COPs between 7.2 and about 4 and COPs in cooling mode Boccardi et al [75,76] also evaluated ejector efficiencies below the ones available in the open literature. This was due to the fact that a multi-ejector module designed for refrigeration applications (i.e., high pressure lift and low mass entrainment ratio) was used.…”

Section: Laboratory Experimental Assessmentsmentioning

confidence: 99%

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Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments

et al. 2019

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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.

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“…A study on a two-ejector system has shown that throttling losses could be substantially reduced, and the heating COP could be increased by about 10% to 30% compared to the basic two-stage cycle with a flash tank [29]. Furthermore, Boccardi et al [30] experimentally studied the benefit of integrating a multi-ejector in a transcritical CO 2 cycle for heating applications. They found that the optimal multi-ejector configuration could reduce the throttling losses by 46%, and, thereby, improve the system performance by up to 30%.…”

Section: Expansion Devicementioning

confidence: 99%

Recent Advances in Transcritical CO2 (R744) Heat Pump System: A Review

et al. 2019

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Heat pump (HP) is one of the most energy efficient tools for address heating and possibly cooling needs in buildings. Growing environmental concerns over conventional HP refrigerants, chlorofluorocarbons (CFCs), and hydrofluorocarbons (HFCs) have forced legislators and researchers to look for alternatives. As such, carbon dioxide (R744/CO2) has come to light due to its low global warming potential (GWP) and zero ozone depleting characteristics. Even though CO2 is environmentally benign, the performance of CO2 HP has been of concern since its inception. To improve the performance of CO2 HP, research has been playing a pivotal role in developing functional designs of heat exchangers, expansion devices, and compressors to suit the CO2 transcritical cycle. Different CO2 HP cycles coupled with auxiliary components, hybrid systems, and refrigerant mixtures along with advanced control strategies have been applied and tested. This paper presents a complete overview of the most recent developments of transcritical CO2 HPs, their components, and applications.

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Thermodynamic Analysis of a Multi-Ejector, CO2, Air-To-Water Heat Pump System

Cited by 16 publications

References 9 publications

Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments

Recent Advances in Transcritical CO2 (R744) Heat Pump System: A Review

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