Utilization of zeotropic Fluid Mixtures in Heat Pumps



Greater Copenhagen area

Heat pumps can constitute a good solution for improving a plants efficiency, by using waste heat at a temperature level above the ambient temperature and a relatively small amount of technical work, to cover a heat demand on a higher temperature. Thus, the emittance of waste heat to the environment decreases and the heat demand at the high temperature level can be covered without additional CO2 production. Altogether, heat pumps can be used to improve the efficiency of existing plants.

One key challenge is an optimal integration of the heat pump into existing processes. In order to minimize the exergy destruction due to heat transfer processes, it is essential to match the temperature profile of the cycle to the temperature profile of the heat source/sink. An improved temperature match can be achieved by employing zeotropic mixtures, which have a non-constant evaporation and condensation temperature.

The utilization of zeotropic mixtures to enhance the efficiency of a heat pump application is a fairly novel approach, and thus, shows a lot of potential as well as risks. Both aspects should be analyzed and evaluated in a student project.

The student project could consider the following aspects:

  • Analysis of different working fluid mixtures
  • Modelling on system level (Modelica, Matlab, EES, …)
  • Problems coming up by utilizing working fluid mixtures for the cycle
    • Drawbacks in component design
    • Influence on component’s cost
  • Opportunities for benefiting from utilization of mixtures
    • Temperature drift
    • Advanced cycle arrangements
    • Enrichment of specific working fluid components (volatile or less volatile components) in high or low pressure side to influence/control the temperature glide in evaporation/condensation
  • Energy/Exergy analysis and possibilities to evaluate the cycle performance
  • Different equipment types
  • Specific case study

Moreover, the specific focus of the project can be discussed and any suggestions from students are very welcome. The candidate will be supervised and supported by members of the Section for Thermal Energy at the Mechanical engineering department. The scope of the course can be adjusted to e.g. a specialization course.

For questions please contact Benjamin Zühlsdorf ( and/or Jonas Kjær Jensen (


Background in Thermodynamics and Energy Engineering, Basic knowledge in modelling of thermohydraulic fluid simulations

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