22 May 2008
Different studies have shown that heat pump systems using the natural,
environmentally friendly refrigerant carbon dioxide are able to achieve higher efficiencies
than systems using conventional refrigerants when warming up heating water or potable hot
water at a high temperature level (55°C-60°C). Instead of an isothermal condensation in
conventional systems, the heat transfer always happens with continuously falling
temperature in the gas cooler. In this paper it is shown, that this physical effect presents a
higher optimizing potential of the high pressure side heat exchanger with regard to the
efficiency of the cycle.
Furthermore, four different concepts of heat delivery are presented. Three concepts contain
a direct heat delivery to the heating system from the gas cooler of the carbon dioxide cycle.
In a further, fourth concept the heating system purchases heat out of the storage tank, which
is charged by the heat pump. The concepts are discussed and evaluated under thermo
dynamical, technical and economical aspects.