General characteristics of the working fluids for LHP cooling system design

The EVAL project aims to create a demonstrator of a passive cooling system, based on a loop heat pipe (LHP) technology, for efficient thermal management of the Ultra High Bypass Ratio (UHBR) engine bleed system valves exposed to a harsh temperature environment.

To achieve this aim, the EVAL team started from a comprehensive study of available working fluids, which have a potential to cope with the target harsh environment and meet the criteria of trade-off analysis such as physical properties (melting and critical temperature, saturated vapour pressure, figures of merit), physical and chemical stability at high temperatures, compatibility with common LHP materials, availability at the market. Also, particular attention is paid to the working fluid environmental impact in terms of ozone-depleting potential (ODP), global warming potential (GWP), compliance with REACH regulations.

This data collection presents characteristics of working fluids collected from various sources (specialized databases e.g. ASHRAE, NIST), research articles, conference proceedings, research projects summary reports, data furnished by the thermal fluid manufacturers) and compiled in three Annexes:

Annex A presents data as for ODP, GWP and REACH compliance for 728 working fluids.

Annex B presents boiling temperature and critical temperature for 728 working fluids.

Annex C presents key thermophysical properties for 32 fluids selected as prospective refrigerants for the EVAL project purposes.

In general, data collection analyses a wide range of working fluid groups: hydrocarbons, oxygenated hydrocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, hydrofluorocarbons, bromocarbons, hydrobromocarbons and halons, fully fluorinated species,  halogenated ethers, fluoroesters, halogenated alcohols,  iodocarbons  special compounds, mixtures, and others.