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

Abstract

Supermarkets are currently one of the most vital service facilities, whose number of installations is ever-growing in both developed and developing countries. On the other hand, these applications feature a copious indirect contribution to the ongoing climate change, as well as a massive use of potent greenhouse gases. In an attempt to promote climatefriendlier technologies in commercial refrigeration sector, "CO2 only" (transcritical CO2 or pure CO2) refrigeration systems have become the mainstream of new food retails worldwide. In particular, in the last few years parallel (or auxiliary) compression has taken root in food retails as a means to enhance the energy efficiency of pure CO2 units. The thermodynamic performance of such a promising solution can be suitably assessed with the aid of the advanced exergy analysis. The results obtained at the design outdoor temperature of 40 °C showed that the main compressor has the highest priority of enhancement, whereas the high-pressure expansion valve needs to be replaced with a device for expansion work recovery. Also, close attention had to be paid to both the gas cooler and the auxiliary compressor. The former can be improved mainly by enhancing the other components, whereas the irreversibilities related to the latter can be decreased by improving both the compressor itself and the remaining components. Finally, the implemented sensitivity analysis revealed that the improvement in the efficiency of the main compressor should be seriously considered on the part of the manufacturers.

Energy and Environmental Assessment of Co2 Booster Refrigeration Cycles With Flooded Evaporators and Parallel Compressor for Supermarkets in Türki̇ye

“…However, CO2 refrigeration systems have some difficulties such as higher equipment costs because of CO2's high working pressures (Goetzler et al, 2014) and critical temperature of CO2 which is 30.98 ℃ causing CO2 systems to operate transcritical (heat rejection at supercritical zone). In the literature review, there are studies dealing with the use and improvement of CO2 refrigeration systems both theoretically (Ersoy and Bilir, 2012;Ge et al, 2015;Gullo and Hafner, 2017;Mylona et al, 2017;Sarkar and Agrawal, 2010;Sawalha, 2008aSawalha, , 2008b and experimentally (Chesi et al, 2014;Fricke et al, 2016;Fritschi et al, 2017;Llopis, Sanz-Kock, et al, 2015;Nebot-Andrés et al, 2021). Alongside these studies focusing on the improvement of the systems, there are also city-based studies (Cui et al, 2020;Gullo et al, 2016;Işık, 2022;Karampour and Sawalha, 2018;Lata et al, 2021;Mitsopoulos et al, 2019;Sooben et al, 2019;Tsamos et al, 2017) to show the outcomes when they are used in supermarkets in daily operations.…”

Energy analysis of dedicated and integrated mechanical subcooled CO2 boosters for supermarket applications

“…Auxiliary compressors extract vapour from the vessel and compress it to the high pressure, thus reducing vessel pressure, reducing the vapour title at the inlet of the evaporators and shortening the refrigerant mass flow through the high-pressure compressor rack. These systems have been analysed theoretically by Gullo and Hafner A. (2017), Karampour and Sawalha (2018), and others.…”