FUCHS activities in the DryFiciency project was the development of lubricants for high temperature heat pumps with DR-2 (= R1336mzz-Z) screw and reciprocating compressor under severe conditions including high temperature and high pressure in the system which leads to a strong dilution by the working fluid as well as a decrease in the viscosity of the lubricant due to the high temperature. “PAG lubricant was selected as this showed good miscibility with DR-2 at high viscosities, a higher viscosity index compared to Ester, and a higher film strength at elevated temperature. The PAG lubricant also exhibited good thermal stability with DR-2 with an optimized additive system”, says Dennis Ebert of RnD Industrial Oils, FUCHS Schmierstoffe.
After a number of trials and tests for both Bitzer and Viking compressors used, including miscibility, pressure viscosity temperature measurements, and sealed tube test / ageing stability test, exciting finding were made that showed the FUCHS Performance lubricant with DR-2 to have good miscibility making it a safe oil transport and reliable heat transfer lubricant. It also demonstrated a good lubrication performance yielding an excellent wear protection for all compressor parts. In addition, it displayed good thermal and chemical stability providing long-term stability of oil / refrigerant in the system. While the compressors operate on different parameters with the Bitzer screw compressor working on 155°C / 18 bar → 9 mm2/s (minimum 6 mm2/s) and Viking reciprocating compressor operating at 104°C / 4,1 bar → 40 mm2/s (minimum 15 mm2/s), one oil can be used for both applications. “This is a great outcome and shows exciting potential for uptake for the performance lubricant with DR-2 as it demonstrates good miscibility and lubrication performance as well as good thermal and chemical stability“ says Ebert. “Thanks to DryFiciency more demonstrations can now be initiated for more industrial applications”.
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