Lessons learned from an oil-free wet compressor

The recently completed LESSON project has identified the sources of losses of an oil-free wet compressor prototype that was built in a previous project. LESSON has focused on modifying the prototype so that the impact of operating in the two-phase region of the working fluid could be determined experimentally. 

Exergy losses 

Wet compression creates near isothermal conditions during compression, resulting in higher isentropic efficiencies of the compressor. It also prevents operating conditions in the superheating zone of the working media of heat pumps. Such operating conditions are associated with large exergy losses and unacceptably high outlet temperatures that cause problems in the compressors of high temperature heat pumps. 

Global performance 

The data collected and reported in the COMPRESORP project relates only to the conditions at the compressor inlet and outlet flanges. With this data, the global performance of the developed model can be validated, but the sources of losses cannot be identified. 

Predicting performance 

The LESSON project ensures that the prototype developed in COMPRESSORP can be validated in more detail. The improved compressor model has been integrated into the full compression resorption heat pump model to predict heat pump performance in high temperature applications. 

Next-generation commercial compressor 

At the same time, a compression-resorption heat pump has been designed in LESSON that integrates the lessons learned. The designed capacity of that heat pump is comparable in size to the current compressor prototype.