CE05 - Une énergie durable, propre, sûre et efficace

Natural Working Fluids for Absorption Refrigeration – AWARE

Submission summary

European and global regulations on greenhouse gases are constantly evolving. Most of the fluorinated refrigerants currently used are close to be banned due to their high global warming potentials.The most widely used refrigeration system is the vapor-compression refrigeration cycle including an electrically driven compressor and hydrofluorocarbon (HFCs) as working fluids. This technology produces both a direct and an indirect contribution to global warming. Indeed HFCs have high global warming potential and their global phased-down has recently started. The indirect contribution is related to the electrical energy production required by the compressor. In order to mitigate greenhouse gas emissions and prevent further environmental degradation, the refrigerant alternatives and the search for alternatives to vapor-compression refrigeration has become more critical.

Vapor-absorption refrigeration technology, driven by thermal energy such as solar energy, geothermal energy, or industrial waste heat, has received growing attention in the past years from air-conditioning and refrigeration applications especially in connection with energy efficiency. In absorption technology the compressor is removed and the pressure variations are related to the refrigerant absorption/separation cycles. The working fluid is a binary system consisting of a refrigerant with high volatility and an absorbent which less volatility but strong affinity to the former. Vapor absorption refrigeration presents several advantages such as a low work input requirement, a fairly simple and economical utilization and the chance to use natural refrigerant/absorbent pairs. Performance of an absorption cycle is critically dependent on the thermodynamic properties of working fluids. Typical commercially available absorption systems use combinations of water+lithium bromide (LiBr) for moderate temperature applications, and ammonia+water for low temperature. Nevertheless, these working fluids exhibit specific issues such as technological challenges, or health hazards, or environmental concerns which prevent wider use.

To overcome these limitations and promote vapor-absorption technology, our goal is to explore a radically different path regarding the search of new natural refrigerant / absorbent pairs. To limit the environmental impact of the working fluid used, the natural refrigerant investigated will be carbon dioxide (CO2 or R744) and the absorbent will be a compound derived from biomass. The detailed knowledge of the thermodynamic properties of the working fluid pairs is crucial to retrofit and modify vapor-absorption process. Moreover process developments require disposing an appropriate thermodynamic model. The project aims to develop an original methodology based on the combination of three complementary scientific fields covering the areas of knowledge required for the design of working pairs for absorption refrigeration namely: the development of simulation tools, the acquisition of new experimental data and the development of thermodynamic models.
We will first focus on the selection of suitable bio-based absorbents to be used with CO2. To achieve this task, a careful review of existing thermophysical data and dynamic molecular simulations of missing key properties will be performed. To assess the potential candidate pairs, the project will be based on experimental measurements of calorimetric and transport properties, and the subsequent design of efficient thermodynamic models. These models will allow the determination of working fluids performances of and efficiency optimization of the thermodynamic cycles.

Project coordination

Yohann COULIER (INSTITUT DE CHIMIE DE CLERMONT-FERRAND)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

ICCF INSTITUT DE CHIMIE DE CLERMONT-FERRAND

Help of the ANR 224,943 euros
Beginning and duration of the scientific project: March 2021 - 42 Months

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