Two research teams from the UJI and the UPNA optimize mixtures and cooling systems to improve the energy efficiency of domestic and industrial equipment

Two research teams from the Universitat Jaume I and the Public University of Navarra have successfully tested new refrigerant mixtures, systems, and components that significantly enhance energy efficiency in this sector. This industry, which accounts for 7.8% of global greenhouse gas emissions, sees an annual increase of over 170 million new domestic units.

The project ‘Advanced multi-stage refrigeration systems for low-temperature applications (HELTHA)’, funded by the State Research Agency under the 2021-2023 State Plan for Scientific, Technical and Innovation Research, which ends in 2025, is working on three aspects: new high-efficiency refrigeration architectures, new refrigerant mixtures and hybrid applications of two technologies (vapour compression and thermoelectricity), which is currently in the development phase.

In the field of new architectures, the groups consider that the joint cascade system (in which there are two circuits thermally linked and in which one is responsible for lowering the temperature of the other) is a promising technology for ultra-low temperature applications, but that more research is needed to improve its energy efficiency. However, they have tested the use of an internal heat exchanger (IHX) with improvements in the coefficient of performance (COP) of up to 5.6%.

With regard to mixtures, several alternatives to isobutane (R600a), for domestic use, and carbon dioxide, used in industry, have been tested with very positive results. In the first case, the RE170/R600 and R290/R600 mixtures have shown superior energy efficiency together with the maintenance of thermodynamic properties, so they could become, in the long term, an option in vapour compression cycles for domestic refrigeration.
In the case of commercial or industrial refrigeration, the CO2/R32 and CO2/R1270 mixtures have shown significant reductions in energy consumption and working pressures, and could be used as an alternative to CO2 and hydrocarbons in systems where the mass load exceeds the limits of the regulations or for safety reasons, although more tests would be needed to check the non-flammability of the mixtures and for possible leaks.

The research team, led by Daniel Sánchez García-Vacas and Rodrigo Llopis Doménech from the Group in Thermal Engineering (GIT), is made up of Ramón Cabello López, Daniel Calleja Anta, Laura Nebot Andrés, Rafael Larrondo Sancho and Manel E. Martínez Ángeles at the UJI. The Thermal and Fluid Engineering Group (ITF) at the Public University of Navarre is directed by David Astráin Ulibarrena and its researchers are Patricia Aranguren Garacochea, Álvaro Casi Satrústegui and Antonio Rodríguez García.

During the development of the project, the research staff has collaborated with other research groups and centres such as the Institute of Thermal Technology at the Silesian University of Technology (Gliwice, Poland); the University of Naples Federico II (Naples, Italy) and the Università degli Studi di Udine (Udine, Italy) and they plan to make contact with several companies in the sector with whom they have previously worked in order to implement the advances made in commercial equipment in which the energy savings obtained can be quantified.

These advances are the result of the R+D+i project (PID2021/126926OB-C21), funded by MICIU/AEI/10.13039/501100011033/ and FEDER/UE. They have also received support from MICIU (PRE2019-091617), the European Union - NextGenerationEU (INVEST/2022/294) and MCIN/AEI/10. 13039/501100011033 and the European Regional Development Fund (ERDF, a way to make Europe) of the EU (TED2021-130162B-I00).

Articles

Daniel Calleja-Anta, Manel Martínez-Ángeles, Laura Nebot-Andrés, Daniel Sánchez, Rodrigo Llopis, Optimizing R152a/R600 and R290/R600 mixtures for superior energy performance in vapor compression systems: Promising alternatives to Isobutane (R600a), Applied Thermal Engineering, Volume 247, 2024, 123070, ISSN 1359-4311. https://doi.org/10.1016/j.applthermaleng.2024.123070.

Rodrigo Llopis, Manel Martínez-Ángeles, Daniel Calleja-Anta, Laura Nebot-Andrés, Energy performance assessment of an auto-cascade cycle for ultra-low temperatures with the pair R1150 - R600a, Applied Thermal Engineering, Volume 240, 2024, 122255, ISSN 1359-4311. https://doi.org/10.1016/j.applthermaleng.2023.122255.

Ramón Cabello, Alejandro Andreu-Nácher, Daniel Sánchez, Rafael Larrondo, Energy influence of the internal heat exchangers placement in a cascade refrigeration plant. A theoretical and experimental analysis, Applied Thermal Engineering, Volume 244, 2024, 122690, ISSN 1359-4311. https://doi.org/10.1016/j.applthermaleng.2024.122690.

D. Sánchez, F. Vidan-Falomir, L. Nebot-Andrés, R. Llopis, R. Cabello, Alternative blends of CO2 for transcritical refrigeration systems. Experimental approach and energy analysis, Energy Conversion and Management, Volume 279, 2023, 116690, ISSN 0196-8904. https://doi.org/10.1016/j.enconman.2023.116690.