A combi storage for combination with heat pumps -from simulations to the test bench results

In this work the development and testing of a combi storage tank for the combination with a heat pump is described. The appropriate size and segmentation of the storage in different zones was determined with simulations in TRNSYS. Installations in the storage tank for efficient handling of the high volume flow rates of a heat pump were designed and selected using CFD simulations. Finally, the finished storage tank was tested to determine its stratification efficiency, demonstrating its good stratification properties. The storage tank performs very well with a stratification efficiency of 84 % at system level. The separation of the temperature ranges for hot water preparation in the storage tank above and the space-heating zone remains intact even when charged with the high mass flow rate of 2570 kg/ h. As a result, the heat pump can be operated with a low supply temperature (the power weighted average supply temperature of the heat pump was 33 degrees C) and thus at a favorable operating point with high efficiency.