Experimental analysis of energy performance of modified single-stage CO2 transcritical vapour compression cycles based on vapour injection in the suction line

Cabello, R.; Sánchez, Daniel; Patiño, J.; Torrella, E.

doi:10.1016/j.applthermaleng.2012.02.031

Cited by 40 publications

(12 citation statements)

References 13 publications

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“…Others analysed experimentally the effect of vapour extraction from the vessel to inject it in different points of the refrigeration cycle. 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.…”

Section: Introductionmentioning

confidence: 97%

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

Llopis

Sánchez

Torrella

2015

International Journal of Refrigeration

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161

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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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Section: Introductionmentioning

confidence: 97%

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

Llopis

Sánchez

Torrella

2015

International Journal of Refrigeration

Self Cite

161

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“…The experimental measurements demonstrated that the IHX can improve the COP up to a maximum of 10 %. 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.…”

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

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131

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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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“…Experimental results showed that the IHX reduces the ejector contribution to the system performance. Cabello et al (2012) presented an experimental analysis of the energetic performances of a modified single-stage CO 2 trans-critical refrigeration plant with an IHX based on vapor injection in suction line. Three different injection points have been evaluated experimentally.…”

Section: Introductionmentioning

confidence: 99%

An experimental study on charge optimization of a trans-critical CO2 cycle

Aprea

Greco

Maiorino

2014

Int. J. Environ. Sci. Technol.

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The phasing out of hydrochlorofluorocarbon and chlorofluorocarbon fluids and further environmental problems arising from new, synthetic working fluids stimulate a continuously rising interest on natural candidates. The nontoxic and nonflammable CO 2 impacts neither on ozone depletion nor on global warming if leaked to the atmosphere. The critical temperature of CO 2 (31.1°C) is almost ambient and, therefore, it undergoes a transcritical refrigeration cycle. In cooling mode operation, a trans-critical CO 2 system, as compared to conventional airconditioners, has a lower performance which, contrary to conventional systems, strongly depends on the refrigerant charge. In this paper, the performance of the trans-critical system was evaluated experimentally under different refrigerant charge amounts. The influence of charge on coefficient of performance (COP), cooling capacity, compression ratio, suction line superheat was analyzed in detail. The experimental results indicate that the COP of the trans-critical cycle attains a maximum at optimal refrigerant charge. By varying the charge the cooling capacity attains a maximum, as well, that corresponds to the optimal charge. In order to understand the effect of refrigerant charge on the performance of each device of the plant, an exergetic analysis based on the experimental data was carried out. The analysis shows that the exergy flow destroyed in the compressor is one of the major causes of overall exergy destruction. At the optimal refrigerant charge, the compression losses attain a minimum.

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Experimental analysis of energy performance of modified single-stage CO2 transcritical vapour compression cycles based on vapour injection in the suction line

Cited by 40 publications

References 13 publications

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

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

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

An experimental study on charge optimization of a trans-critical CO2 cycle

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