Veronika Wilk of AIT led a stimulating discussion on the open-loop heat pump system developed by the DryFiciency consortium using advanced, low-cost, turbo-compressor technology by ROTREX originating from the automotive sector. While normal automotive applications deal with temperatures of up to 50°C and ambient pressure, DryFiciency demands nearly 300 % higher temperatures along with steam and over pressure at inlet. In order to manage this the compressors underwent a number of designs and tests under extreme conditions. Søren Schmid of ROTREX demonstrated how the new designs simulated impeller design, utilised highly specialised hydrodynamic sealing solutions and special compression design utilising integrated lubrication circuits to achieve the DryFiciency requirements.
In the closed-loop heat pump systems, also known as compression heat pumps, Loic Chereau of Chemours showed how the HFO-1336mzz(Z) refrigerant has demonstrated excellent chemical and material compatibility to higher temperature levels and has now been confirmed to be a viable working fluid in waste heat recovery applications. Joined by Dennis Ebert of Fuchs Schmierstoffe it was further confirmed that the newly developed FUCHS lubricants had good miscibility with DR-2 at high viscosities and a good thermal stability with an optimised additive system.
The compressor technologies of Bitzer and Heaten have been put to the test with these fluids at various temperatures and have shown as viable solution in the next generation of compressors for high temperature heat pumps. As demonstrated by Julian Pfaffl of BITZER, this knowledge has now been used to further develop the next generation of compressor technology being tested in a hybrid solution for high temperature applications.
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