Experimental evaluation of a CO2 transcritical refrigeration plant with dedicated mechanical subcooling

Llopis, Rodrigo; Nebot‐Andrés, Laura; Sánchez, Daniel; Catalán‐Gil, Jesús

doi:10.1016/j.ijrefrig.2016.06.009

Cited by 131 publications

(59 citation statements)

References 18 publications

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“…The following are samples of the researches which investigate the positive impacts of single modifications; single or multi-ejectors ) (Gullo et al, 2017) (Schönenberger et al, 2014), parallel compression (Javerschek et al, 2015) (Javerschek et al, 2016) , flooded evaporation (Minetto et al, 2014a) (Tambovtsev and Quack, 2007), mechanical sub-cooling (Llopis et al, 2016a) (Bush et al, 2017), evaporative cooling (Girotto and Minetto, 2008) (Lozza et al, 2007), and LT de-superheater (Llopis et al, 2016b).…”

Section: Introductionmentioning

confidence: 99%

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

Karampour

Sawalha

2018

International Journal of Refrigeration

127

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This paper investigates the integrated and state-of-the art features of CO 2 trans-critical booster systems. The main objective is to identify the most promising solutions in terms of energy efficiency impacts.First, the performance of modified features and integrated functions have been compared with the standard CO2 system and alternative heating and air conditioning solutions. Subsequently, the performance of the defined state-of-the-art CO 2 system is compared to natural refrigerant-based cascade and HFC/HFO-based DX and indirect refrigeration solutions operating in cold and warm climates.The results indicate that two-stage heat recovery, flooded evaporation, parallel compression and integration of air conditioning are the most promising features of the state-of-the-art integrated CO2 system. This compact and environmentally friendly system is the most energy efficient solution in cold climates, and is also an efficient solution in warm climates, with comparable efficiency to cascade and HFC/HFO DX systems, but with no existing or potential limitations.

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Section: Introductionmentioning

confidence: 99%

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

Karampour

Sawalha

2018

International Journal of Refrigeration

127

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“…This study showed the existence of an optimum pressure and, evaluating different subcooling degrees, it was observed that the improvement was greater for the highest subcooling degree (10 K). Later, these results were corroborated experimentally, where increments up to 26.1% in COP and 39.4% in cooling capacity are obtained for 40 • C of heat rejection temperature and an evaporating level of 0 • C [11]. These experiments were optimized in terms of discharge pressure but the subcooling degree was not optimized.…”

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confidence: 71%

Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

et al. 2019

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Different alternatives are being studied nowadays in order to enhance the behavior of transcritical CO 2 refrigeration plants. Among the most studied options, subcooling is one of the most analyzed methods in the last years, increasing cooling capacity and Coefficient Of Performance (COP), especially at high hot sink temperatures. A new cycle, called integrated mechanical subcooling cycle, has been developed, as a total-CO 2 solution, to provide the subcooling in CO 2 transcritical refrigeration cycles. It corresponds to a promising solution from the point of view of energy efficiency. The purpose of this work is to present, for the first time, thermodynamic analysis of a CO 2 refrigeration cycle with integrated mechanical subcooling cycle from first and second law approaches. Using simplified models of the components, the optimum operating conditions, optimum gas-cooler pressure, and subcooling degree are determined in order to obtain the maximum COP. The main energy parameters of the system were analyzed for different evaporation levels and heat rejection temperatures. The exergy destruction was analyzed for each component, identifying the elements of the system that introduce more irreversibilities. It has been concluded that the new cycle could offer COP improvements from 11.7% to 15.9% in relation to single-stage cycles with internal heat exchanger (IHX) at 35 • C ambient temperature.Energies 2020, 13, 4 2 of 17 the parallel compressor in a real plant, which lead to increments in COP not as promising as the theoretical results. Also, the use of ejectors is widely studied as a way to improve CO 2 installations either using multi-ejectors [6] or adjustable ejectors [7]. Even with the promising results of this solution, the operation and control remain complex.The other great research line is focused on subcooling methods [8]. The purpose of subcooling methods is to subcool the CO 2 at the exit of the gas-cooler, which increases the COP of the plant due to the increment on the specific cooling capacity, the reduction of the optimum working pressure, and the reduction of the specific compression work [9]. First, studies show that when the subcooling is higher, the increments are higher. However, not all the subcooling systems have the same performance, nor the same range of application. The improvements they can produce depend on the cost of the subcooling and on the working conditions. To obtain the greatest benefits of this type of system, they must be optimized in terms of pressure and subcooling degree to achieve maximum COP. In addition to the benefits that contribute to the energy efficiency of the plant, these systems also have benefits from an exergy analysis. The reduction of the optimum pressure and the subcooling allow for reducing the exergy destruction that takes place in the expansion process, leading to configurations with greater exergy performance.The main subcooling methods are classified as internal methods and dedicated subcooling methods. The first studied method and widely applied in applic...

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“…Table presents a review of different techniques, their advantages, and limitations in technology adaptation. Nowadays, the modifications in the CO 2 refrigeration cycles are in progress with researcher enhancing the performance with different techniques like single or multiejectors, two‐stage CO 2 compressors, parallel compression, ejectors, MAC applications in automobile industry, flooded evaporation, mechanical subcooling, absorption subcooling, thermoelectric subcooling, evaporative precooling, vortex tube, and expanders to enhance the energy efficiency, COP, and safety.…”

Section: History Of Refrigerantsmentioning

confidence: 99%

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

2019

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Summary Refrigerants bearing high global warming potential (GWP) and ozone depletion potential (ODP) were outlawed or facing time‐beared permission under the Montreal (1987), Kyoto (1997) protocols, F‐Gas law (2015), Paris Accord (2016), and recent Kigali Amendment to Montreal Protocol (2019). In order to modify followed by the paradigm shift of existing heating and cooling systems, American Society of Heating, Refrigeration, and Air‐Conditioning Engineers (ASHRAE) envisaged natural and synthetic refrigerants (Synrefs) are under investigation globally. Carbon dioxide (CO2) is a popular natural refrigerant (Natref) replacing Synrefs used in commercial heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems globally. A rampant rise is observed in markets of Asia (Japan and China), North America (the United States and Canada), the Australian continent, and Africa (South Africa) by reaching 20 000 CO2‐stores around the globe. The European markets are leading the utilization of CO2 in the heat pump, and refrigeration, CO2 based markets estimate 14% of the total food retail stores (400 m2). Japan is the second leading market of CO2 heat pump and refrigeration with more than 10 200 CO2 condensing units. CO2 transcritical systems have a share of more than 10% in only European market (large stores); however, their share is less than 10% of total stores in other major markets of the world. New pump and compressor‐driven transcritical CO2 systems integrate ejectors, condensers, and booster systems to reduce energy consumptions, enhance efficiency, efficacy, and coefficient of performance. This article reports a critical review of the CO2 based heating, cooling, and refrigeration system and presents updated literature along with barriers and challenges on commercial use of Natref‐based heating and cooling applications worldwide.

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Experimental evaluation of a CO2 transcritical refrigeration plant with dedicated mechanical subcooling

Cited by 131 publications

References 18 publications

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

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Experimental evaluation of a CO2 transcritical refrigeration plant with dedicated mechanical subcooling

Cited by 131 publications

References 18 publications

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

Review of carbon dioxide (CO 2 ) based heating and cooling technologies: Past, present, and future outlook

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Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook