Studies on the performance of a CO2 air conditioning system using an ejector as an expansion device

Lee, Jae Seung; Kim, Mo Se; Kim, Min Soo

doi:10.1016/j.ijrefrig.2013.08.019

Cited by 40 publications

(13 citation statements)

References 10 publications

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“…Others analyzed the effect of extracting vapour from the intermediate vessel to be injected in different points of the cycle, measuring maximum increments of 7 % in single-stage plants (Cabello et al, 2012) and 16.5 % in double-stage cycles (Cho et al, 2009). The use of expanders (Li et al, 2004), ejectors (Lee et al, 2014) and regulation strategies (Peñarrocha et al, 2014) are also considered. And now the improvements of the CO2 transcritical plants are looked for its combination with other systems, such as desiccant wheels (Aprea et al, 2015) or absorption plants (Arora et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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

Llopis

Nebot‐Andrés

Sánchez

et al. 2016

International Journal of Refrigeration

130

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CO2 transcritical refrigeration cycles require optimization to reach the performance of conventional solutions at high ambient temperatures. Theoretical studies demonstrated that the combination of a transcritical cycle with a mechanical subcooling cycle improves its performance; however, any experimentation with CO2 has been found. This work presents the energy improvements of the use of a mechanical subcooling cycle in combination with a CO2 transcritical refrigeration plant, experimentally. It is tested the combination of a R1234yf single-stage refrigeration cycle with a semihermetic compressor for the mechanical subcooling cycle, with a single-stage CO2 transcritical refrigeration plant with a semihermetic compressor. The combination is evaluated at two evaporating levels of the CO2 cycle (0 and -10 ºC) and three heat rejection temperatures (24, 30 and 40 ºC). The optimum operating conditions and capacity and COP improvements are analysed with maximum increments on capacity of 55.7 % and 30.3 % on COP. KEYWORDS

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Section: Introductionmentioning

confidence: 99%

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

Llopis

Nebot‐Andrés

Sánchez

et al. 2016

International Journal of Refrigeration

130

View full text Add to dashboard Cite

show abstract

“…The improvements of COP reached up to 7% in single-stage cycles (Cabello et al, 2012) and 16.5% in double-stage plants (Cho et al, 2009). Other improvements are the use of expanders (Li et al, 2004;Yang et al, 2007) and ejectors (He et al, 2014;Lee et al, 2014) to reduce irreversibilities during the expansion process, which also offered COP increments. In parallel, control strategies to regulate the heat rejection pressure were developed (Aprea and Maiorino, 2009;Ge and Tassou, 2009;Peñarrocha et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Energy improvements of CO 2 transcritical refrigeration cycles using dedicated mechanical subcooling

Llopis

Sánchez

Torrella

2015

International Journal of Refrigeration

157

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In this work the possibilities of enhancing the energy performance of CO2 transcritical refrigeration systems using a dedicated mechanical subcooling cycle are analysed theoretically. Using simplified models of the cycles, the modification of the optimum operating conditions of the CO2 transcritical cycle by the use of the mechanical subcooling are analysed and discussed. Next, for the optimum conditions, the possibilities of improving the energy performance of the transcritical cycle with the mechanical subcooling are evaluated for three evaporating levels (5, -5 and -30 ºC) for environment temperatures from 20 to 35 ºC using propane as refrigerant for the subcooling cycle. It has been observed that the cycle combination will allow increasing the COP up to a maximum of 20% and the cooling capacity up to a maximum of 28.8%, being both increments higher at high evaporating levels. Furthermore, the results indicate that this cycle is more convenient for environment temperatures above 25 ºC. Finally, the results using different refrigerants for the mechanical subcooling cycle are presented, where no important differences are observed. KEYWORDS

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“…Most recent investigations have been concentrated on transcritical R744 ejector-expansion refrigeration cycles (EECs) because of the large improvement potential owing to the high throttling loss [1][2][3][4][5][6][7][8][9][10][11]. Subcritical EECs have received much less attention because these cycles offer relatively lower improvement potential through the ejector action.…”

Section: Introductionmentioning

confidence: 99%

Energetic and Exergetic Analysis of an Ejector-Expansion Refrigeration Cycle Using the Working Fluid R32

Zhang

Tong

Chang

et al. 2015

Entropy

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Abstract:The performance characteristics of an ejector-expansion refrigeration cycle (EEC) using R32 have been investigated in comparison with that using R134a. The coefficient of performance (COP), the exergy destruction, the exergy efficiency and the suction nozzle pressure drop (SNPD) are discussed. The results show that the application of an ejector instead of a throttle valve in R32 cycle decreases the cycle's total exergy destruction by 8.84%-15.84% in comparison with the basic cycle (BC). The R32 EEC provides 5.22%-13.77% COP improvement and 5.13%-13.83% exergy efficiency improvement respectively over the BC for the given ranges of evaporating and condensing temperatures. There exists an optimum suction nozzle pressure drop (SNPD) which gives a maximum system COP and volumetric cooling capacity (VCC) under a specified condition. The value of the optimum SNPD mainly depends on the efficiencies of the ejector components, but is virtually independent of evaporating temperature and condensing temperature. In addition, the improvement of the component efficiency, especially the efficiencies of diffusion nozzle and the motive nozzle, can enhance the EEC performance.

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Studies on the performance of a CO2 air conditioning system using an ejector as an expansion device

Cited by 40 publications

References 10 publications

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

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

Energy improvements of CO 2 transcritical refrigeration cycles using dedicated mechanical subcooling

Energetic and Exergetic Analysis of an Ejector-Expansion Refrigeration Cycle Using the Working Fluid R32

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