Energy and environmental performance assessment of R744 booster supermarket refrigeration systems operating in warm climates

Abstract

This paper presents a theoretical comparison among different commercial refrigeration systems in terms of annual energy consumption and environmental impact. Eight configurations were studied: a R744/R134a cascade refrigeration system (baseline), a conventional and an improved R744 booster system, two R744 booster solutions with dedicated mechanical subcooling, a R744 booster with parallel compression and two solutions which combined the parallel compression and the mechanical subcooling. The evaluation was based on the weather data in Valencia (Spain) and in Athens (Greece), as well as on the running modes of a conventional European supermarket. A transition zone, which occurred between subcritical and transcritical operations, was adopted.\ud The results showed that all the enhanced configurations may achieve a comparable energy saving to the one of the baseline in both the selected locations. Furthermore, they allow reducing the Total Equivalent Warming Impact (TEWI) by at least 9.6% beside the cascade solution

Thermodynamic performance evaluation of the CO 2 parallel compression supermarket refrigeration system with a subcooler

“…Other components with high exergy destruction rates include HP control valve (12.76%), MT evaporator (12.88%) and gas cooler (18.15%). When the ambient temperature rises to 35°C, the exergy destruction rate of HP Control valve accounts for 18.7%, according to the research results of Gullo et al 10 ; with the increase of the outdoor temperature, the pressure on the high‐pressure side will also increase, which will enhance the irreversibility in the process of throttle and reduce the efficiency of the SPR system.…”

“…The arrangement of the parallel solution is similar to the booster solution, except that the vapor from the liquid receiver is sent to an auxiliary compressor instead of the high‐pressure compressor. Auxiliary compressor, as one part of the parallel compression system, hence can provide a more efficient compression process for this strand of vapor to improve the system performance especially when the outdoor temperature is higher above 14°C 10,11 . And energy consumption in the booster system with both auxiliary compressor and water tank can be reduced by 9% compared with the system without auxiliary compressor 12 .…”

“…Llopis et al applied the integrated mechanical subcooler in Europe and China and achieved a reduction in energy consumption of approximately 5% 20 . Recently, for R744 trans‐critical cycle, mechanical subcooling was proposed by Gullo and Llopis et al that the subcooling is provided by another dedicated refrigerating unit, 21 . by which the COP of a single temperature level refrigeration system can be improved from 9.5% to 13.7% 20 .…”

Thermodynamic Performance Assessment of a CO2 Supermarket Refrigeration System with Auxiliary Compression Economization by using Advanced Exergy Analysis

“…The former is used for removing the vapor generated by the high-pressure expansion valve (TV(HP)) from the REC. It is worth remarking that the higher the outdoor temperature, the more vapor is produced [5]. Two main benefits can be associated with this solution in relation to a conventional transcritical R744 unit, i.e.…”

CO2 with Mechanical Subcooling vs. CO2 Cascade Cycles for Medium Temperature Commercial Refrigeration Applications Thermodynamic Analysis

“…at. [16] and Llopis et al [17], and from an experimental point of view by Nebot-Andrés et al [18] and Eikevik et al [19]. This cycle is characterized by a main refrigeration cycle working with CO 2 that can be operated in subcritical or transcritical modes which is helped by another vapor compression system, the dedicated mechanical subcooling cycle, providing CO 2 a large subcooling at the exit of the gas-cooler/condenser.…”