The transformation of heat supply in urban areas from fossil based to renewable is a key factor to reduce the CO2
emissions. Every existing district network has its own characteristics in heat supply temperature (>90°C), capacity,
age, heat generation technology, and options to change the volume flow to keep the heat supply costs low.
Decentralized non-used heat sources in urban areas can be implemented with multi-source heat pumps. These sources
could be cold water networks, sewage up to server farms and low- and mid-temperature district heating networks. The
challenge for multi-source heat pumps are the different temperature levels of each source. To investigate different
multi-source scenarios for heat pump technology a fluid screening has been the foundation for a test rig design;
different compressor configurations are also analyzed in order to consider the entire improvement potential integrally.
Regarding the working fluids the focus will be hydrocarbon refrigerants and mixtures for heat pump heating capacity
of 5 to 50 kW. The source temperatures are varied between -10 °C and 50 °C, the sink temperatures between 30 °C
and 85 °C. The temperature spread between inlet and outlet of the heat source/heat sink is investigated between 5 and
25 K. The focus of the system is the compression technology: A scroll compressor and two reciprocating compressors
are installed and can be tested separately or in a booster option with an intercooling. A comparison and interaction
between refrigerant mixtures, compressor technology, source/sink temperature and temperature glide should be
enabled.