23 September 2011
Air/water heat pumps require only low investments, are easy to install and reliable
in their operation. However, one of the most important prerequisites for the increasing
proliferation of air/water heat pumps lies in the substantial increase of their efficiency.
Theoretical and experimental analyses indicate that the exergetic efficiency of common
air/water heat pumps become smaller when the ambient temperature increases. As a
consequence, a substantial increase in efficiency requests continuous operation with capacity
control of the compressor and the fan. The aim of this project is to develop universally valid
design and planning criteria for the realisation of efficient, reliable and economic air/water
heat pumps with continuous capacity control. An optimised process control strategy was
developed using simulations as well as experiments with a prototype. The experimental
investigations approve the great potential of the capacity control. As a result the seasonal
performance factor can be increased by approximately 10 to 60% compared to air/water heat
pumps with on/off control.