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Comparative analysis of HFO-CO2 cascade vs CO2 transcritical refrigeration systems in two supermarkets. Part II: Evaluation of heat recovery and integration of heat pumps based on field measurements
Univ Padua, Dipartimento Ingn Ind, Padua, Italy.
Frigoveneta SpA, Villa Bartolomea Verona, Italy.
Univ Padua, Dipartimento Ingn Ind, Padua, Italy.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.ORCID iD: 0000-0003-0911-0786
2025 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 177, p. 156-167Article in journal (Refereed) Published
Abstract [en]

This study examines heat recovery from refrigeration systems and the operational benefits of integrating heat recovery in two medium-sized supermarkets in northern Italy based on field measurements. A supermarket operates with a R1234ze/CO2 cascade system, which is integrated with heat pumps, and the other is a CO2 transcritical system. The system description, along with the processes of data collection and validation, is discussed in detail in part I of the article. Both systems are equipped with heat recovery and began operating in 2023. The floating condensation model was developed in MATLAB, utilizing REFPROP to calculate the coefficient of performance (COP) of heat recovery. Furthermore, the COP of heat pumps and the COP of each stage in floating condensation mode are calculated. Results show R1234ze/CO2 cascade system integrated with a heat pump and air conditioning fully meets the cooling and heating demands of the supermarket's sales area, by using 12 % more annual electricity compared to the floating condensation mode. The continuous heat recovery in the R1234ze/CO2 cascade system leads to a higher amount of heat recovery compared to the CO2 transcritical system. The heat recovery of the CO2 transcritical system is not used as a main source to cover the heat demand. In this system, due to lower heat demand, heat recovery most often occurs in subcritical mode, and it does not fully utilise its heat recovery potential. Only 39 % of the total heat recovered occurs in transcritical mode, with the remaining heat rejected to the air. COP of heat recovery of this system is higher than the cascade system; however, the values in both systems for ambient temperature lower than 4 degrees C are comparable. Furthermore, the results show that in floating condensation mode, the COP of the CO2 transcritical system in the MT and LT stages is higher than the cascade system at temperatures below 16 degrees C and 9 degrees C, respectively, this trend reverses at temperatures above these values. The global COP of the cascade system consistently remains higher than that of the CO2 system.

Place, publisher, year, edition, pages
Elsevier BV , 2025. Vol. 177, p. 156-167
Keywords [en]
Heat recovery, Heat pump, Field measurement, Supermarket refrigeration, CO2 transcritical system, HFO-CO2 cascade system
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-369309DOI: 10.1016/j.ijrefrig.2025.06.003ISI: 001511321400001Scopus ID: 2-s2.0-105007684867OAI: oai:DiVA.org:kth-369309DiVA, id: diva2:1999852
Note

Correction in doi 10.1016/j.ijrefrig.2025.07.018

QC 20250925

Available from: 2025-09-22 Created: 2025-09-22 Last updated: 2025-09-25Bibliographically approved

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Sawalha, Samer

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