Efficient use of low temperature heat sources: High performance heat pump cycles with zeotropic mixtures

  • Benjamin Zühlsdorf (Guest lecturer)

Activity: Talks and presentationsConference presentations


The intended phase out of fossil fuels and the according, inevitable shift to renewable energy sources increased the potential for heat supply with heat pumps. Despite these increasingly attractive conditions for heat pumps and the availability of efficient heat pumps for different applications, there are different hurdles, which hinder heat pumps being implemented more frequently. One of these hurdles is a limited integration of the heat pump into the boundary conditions of the system and the resulting decreased effectiveness, especially for applications with a large temperature glide in sink and source. Therefore, the project focused on the development of a procedure, which analyses the irreversibilities of the heat pump cycle, accounts the inefficiencies to the components and the working fluid and derives based on that recommendations for improvements. One approach to optimize the cycle and enable an improved integration into the boundary conditions is the consideration of zeotropic mixtures as working fluids. By matching the temperature glide in sink and source with the temperature glide of the working fluid during phase change, the exergy destruction due to heat transfer is decreased and the overall efficiency increased. Nevertheless, the identification of a beneficial working fluid mixture requires a comprehensive screening. Finally, it could be shown, that a good choice can improve heat pump cycles dependent on the boundary conditions by more than 10 % to 30 % without adding additional equipment. The presentation will give an overview of the procedure and expectable improvements in thermodynamic and economic performance resulting from the use of mixed working fluids. It will be demonstrated by applications to different industrial case studies. Furthermore, it will be discussed which possible additional benefits and difficulties result from the use of mixtures as working fluids.
Period24 Oct 2017
Event titleEuropean Heat Pump Summit: Powered by Chillventa
Event typeConference
LocationNürnberg, Germany
Degree of RecognitionInternational


  • Zeotropic working fluid
  • Working fluid mixture
  • heat pump
  • integration
  • waste heat recovery