Booster heat pump with zeotropic mixtures

  • Benjamin Zühlsdorf (Guest lecturer)

    Activity: Talks and presentationsConference presentations


    This study analysed a booster heat pump, which was designed for district heating networks operating at 40 °C to elevate the temperature of the forward stream to 60 °C, by using part of the stream as heat source while cooling it down to the return temperature of 25 °C. The proposed optimization approach demonstrated an increase in the thermodynamic performance, which was achieved by using mixed refrigerants.
    The screening of working fluids considered 18 pure working fluids and all possible binary mixtures of these fluids. The most promising solutions were analysed with respect to their performance under conditions deviating from design conditions and their economic potential.
    The best-performing mixture showed a COP of 9.01 and thereby outperformed R134a by 47 %. Although the mixed working fluids resulted in higher investment cost, the economic performance was comparable to the pure fluids. The mixtures showed similar behaviour as the pure fluids for varying operating conditions.
    It was concluded that the mixtures 50 % Propylene / 50 % Butane or 50 % R1234yf / 50 % R1233zdE could considerably improve the thermodynamic performance of the overall heat supply system while being sustainable and economically competitive under the assumed economic boundary conditions.
    Period12 Sept 2017
    Event title3rd International Conference on Smart Energy Systems and 4th Generation District Heating
    Event typeConference
    Conference number3
    LocationCopenhagen, DenmarkShow on map
    Degree of RecognitionInternational


    • Booster heat pump
    • Ultra-low-temperature district heating
    • zeotropic mixture
    • Working fluid mixture