Heating grids are a key component of future heat supply. However, the design of these networks varies
all over Europe. Due to regionally varying specifications for the heating grid structure, it is not possible
to standardize the grid supply and return flow temperatures. Therefore, heat pumps are usually
customized for individual heating grids, which increases planning effort and system costs. To accelerate
the energy transition, a single heat pump capable of operating efficiently within different grids would
be highly beneficial and could significantly simplify implementation. Numerous theoretical studies have
shown that hydrocarbon mixtures offer significant potential, with efficiency improvements compared to
pure substances. These mixtures allow for better adaptation to varying temperature levels and operating
conditions.
For this reason, a dedicated test facility was constructed to investigate the system efficiency by
comparing different hydrocarbon mixtures and various compressor technologies.
The test rig architecture is a 5-component cycle with booster options of the implemented compressors.
A broad variation of temperatures and spreads have been tested on the condenser and the evaporator. In
this study, experimental results and system behavior for propane/butane mixtures up to 85 °C using
scroll compressor are presented. Temperatures up to approximately 140 °C (depending on the mixture)
were analyzed using a simulation model. The results indicate an enhanced coefficient of performance
for the mixtures compared to the pure fluids in most cases, primarily due to improved temperature
matching in both the evaporator and the condenser. Additional factors, such as compressor efficiency
and other effects, may also impact overall system performance and will be the subjects of further
investigation.