REFRIGERANTS | PROPANE (evaporator, compressor, condenser, heat exchanger and expansion valve) in a variety of different configurations. These modules are measured on test rigs 24 hours a day, for two weeks at a time. Each prototype is run at between 30 and 150 operating points, and the measured values are recorded by 26 sensors. In the search for the ideal heat pump, 26 prototypes have been built. As reported by Fraunhofer in October 2022, the system with the best component configuration achieved a maximum heating capacity of 12.8kW and an efficiency of 4.7 (ratio of heat generated to electricity used) with only 124g of propane. That means the amount of refrigerant required per kilowatt of heating capacity was only 9.7g of propane. The projects goal of reducing the amount of refrigerant to 15-30g/kW has been exceeded. Commercially available heat pumps use about 60g of propane per kW. The record-breaking refrigeration circuit4 is not yet ready for market, as it employs a semihermetic automotive compressor. This requires less refrigerant at a higher capacity thanks to its high rotational speed and low oil volume. So far, automotive compressors have not been designed for the high operating hours of a heat pump that is meant to last 20 years. However, the manufacturer is already working on fully hermetic compressors with a longer service life, says Clemens Dankwerth, of Fraunhofer ISE. The final version of the refrigeration circuit would be implemented with slightly more refrigerant and a larger heat exchanger, to achieve a more balanced system. The team is confident that the goals of the project a refrigeration circuit with an output of 8-10kW and maximum charge of 150g can be achieved under real operating conditions. The second-best refrigeration circuit in the test programme so far also met the projects targets, with a charge of 164g of propane at an efficiency of 4.8% and a heating capacity of 8.1kW. Heat pump test rigs running 24 hours a day The goal of reducing the amount of refrigerant to 15-30g/kW has been exceeded A conventional fully hermetic compressor was used here. In addition to the compressor, the research team adjusted other factors to reduce the amount of refrigerant. For example, the internal volume of the heat exchangers and the amount of oil required have been reduced. Additional components, such as sensors, have also been kept to a minimum, and the piping was kept as short as possible to reduce the internal volumes. The LC150 project is funded by the German Federal Ministry for Economic Affairs and Climate Action and runs until March 2023. CJ References: 1 Intergovernmental Panel on Climate Change (IPCC), Climate change 2021: The physical science basis 2 Defra, F-Gas Regulation in Great Britain Assessment, December 2022, bit.ly/CJFeb23R2901, accessed 24 January 2023 3 BS IEC 60335-2-40:2022 ED7 Household and similar electrical appliances. Safety. Part 2-40: Particular requirements for electrical heat pumps, air conditioners and dehumidifiers (pending approval) 4 Fraunhofer ISE, Propane-based refrigeration circuit for heat pumps achieves new efficiency record, bit.ly/CJFeb23R2902, accessed 24 January 2023 FLOOR MOUNTED LIFTING STATIONS DrainMajor 0118 9821 555 Compli 400 Authorised by Jung Pumpen GmBH POWERED BY 54 February 2023 www.cibsejournal.com Compli 1000 Compli 2500 www.jung-pumps.co.uk www.pumptechnology.co.uk