Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study

Gullo, Paride; Tsamos, Konstantinos M.; Hafner, Armin; Banasiak, Krzysztof; Ge, Y.T.; Tassou, S.A.

doi:10.1016/j.energy.2018.08.205

Cited by 53 publications

(29 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These involve the implementation of parallel compression [10][11][12], the use of cold thermal energy storages [13,14], the adoption of overfed evaporators [15][16][17], and the enhancement of the gas cooler performance [18,19]. The combination of some of the aforementioned expedients through the adoption of the multi-ejector concept [20][21][22] has been demonstrated to be the most promising solution to finally open the doors to transcritical R744 supermarket refrigeration plants in any climate context [9]. As an example, the results obtained by Hafner et al [23] showed that the use of a multi-ejector module on the part of "CO 2 -only" supermarket refrigeration units permits energy conservations by 11% in Southern Europe over a solution with parallel compression.…”

Section: R404a-based Unitmentioning

confidence: 99%

“…Additionally, the intermediate pressure (i.e., pressure at RC) was maintained as 35 bar for CB [22]. Furthermore, the pressure drop was considered negligible, and all the heat exchangers were supposed to be well-insulated [21,22]. As demonstrated by many authors [37][38][39], an optimum discharge pressure, maximizing the coefficient of performance (COP), has to be assessed with respect to the gas cooler outlet temperature at high heat sink temperatures, i.e., as the transcritical running modes occur.…”

Section: Assumptions In Common In All Implemented Analysesmentioning

confidence: 99%

“…Additionally, the power input associated with the fans was estimated to be 3% of the heat capacity rejected through the gas cooler/condenser [21,22]. In addition, the performance of the selected compressors was evaluated with the aid of the correlations presented in Table 5, which were obtained by using some manufacturer's software.…”

Section: Parameter Numerical Value Unit Of Measurementmentioning

confidence: 99%

See 2 more Smart Citations

Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis

2019

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: R404a-based Unitmentioning

confidence: 99%

Section: Assumptions In Common In All Implemented Analysesmentioning

confidence: 99%

Section: Parameter Numerical Value Unit Of Measurementmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis

2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Also it is inexpensive refrigerants compared with HFC. Besides its advantages, there are several disadvantages coming along with using R744 refrigerant, especially high operating pressures and low efficiency levels at high ambient temperatures [1][2][3]. There are two types of systems with the use of R744, subcritical and transcritical.…”

Section: Introductionmentioning

confidence: 99%

The performance evaluation of R744 transcritical ejector and R290/R744 cascade refrigeration systems for Turkey

Yılmaz

Mançuhan

2019

THERM SCI

View full text Add to dashboard Cite

In this study, performance of two different environmentally friendly systems with natural refrigerant solutions, R744 transcritical booster system with ejector and a R290/R744 cascade system are examined theoretically by using engineering equation solver software. Operating conditions are determined to represent different climatic regions in Turkey using summer dry bulb temperatures of various cities. The transcritical and the cascade system are assumed to operate at two different evaporation temperatures of-10 °C and-32 °C. The overall energy efficiency ratio values for each system with respect to the same ambient and evaporation conditions are compared and evaluated. Finally, performance of both systems has been compared and the appropriate solution for each city has been suggested. For cold and mild climate regions of Turkey, the performance of transcritical alternative is found better than the proposed cascade system. Moreover, the performance of transcritical system is observed slightly lower than those of the cascade system in hot climate regions of Turkey such as Aegean, Mediterranean, and SouthEast Anatolian regions. It is also found that the performance of the transcritical system is better in regions having lower ambient conditions such as near the Black Sea and eastern regions of Turkey. Therefore, for the mild and cold regions of Turkey, the transcritical ejector option is the better alternative due to having higher performance compared to the cascade system.

show abstract

“…parallel compression [6][7][8], which represents the first step towards of the adoption of "CO 2 only" supermarket refrigeration systems in high ambient temperature countries; • cold thermal energy storages [9,10], which allows reducing the energy consumption by shifting a part of the refrigeration load from more adverse (i.e., daytime) to more advantageous (i.e., night-time) operating conditions; • the implementation of the recovery of part of the available expansion work via two-phase ejectors [11][12][13], giving rise to a significant enhancement in overall thermodynamic performance. The conventional expansion valve, in fact, is responsible for the largest irreversibilities in basic transcritical CO 2 refrigerating cycles [14] and, thus, for the significant penalization in their efficiencies as the cooling medium temperature goes up.…”

mentioning

confidence: 99%

Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling

Gullo

2018

Energies

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study

Abstract: Gullo (a) , Konstantinos M. Tsamos (b) , Armin Hafner (a) , Krzysztof Banasiak (c) , Yunting T. Ge (d) and Savvas A. Tassou (b)

Cited by 53 publications

References 36 publications

Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis

Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis

The performance evaluation of R744 transcritical ejector and R290/R744 cascade refrigeration systems for Turkey

Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling

Contact Info

Product

Resources

About