Integration of a latent heat storage in VRF systems for heating and cooling with enhanced flexibility and efficiency.

In commercial and large office buildings, depending on external loads and different internal loads, heating and cooling phases may occur alternately in the course of the day or even simultaneously. In particular at the occurrence of simultaneous heating and cooling demand VRF (Variable refrigerant flow) systems are favorable compared to separate systems for cooling and heating. However, usually there is only a small overlap of heating and cooling periods. To further increase the heat recovery potential a thermal storage is required. With regard to the characteristics of compression heat pumps, a latent storage avoids the unfavorable temperature rise. For the integration of a latent heat storage in a refrigerant cycle of a VRF system, there are several possible configurations, aiming at different functions and different temperature levels of heat utilization. By using a dynamic model of the VRF system, the energy savings potential and target values for dimensioning and design of the latent heat storage are derived.