A comparative study on system performances of multi-split air source heat pump with different energy accumulators and storage methods

Adding an energy accumulator to an air source heat pump (ASHP) unit can significantly improve its defrosting performances. However, the added energy accumulator may impact the system performances during heating period, which was rarely investigated in the published studies, especially for multi-split ASHP units (a kind of more and more widely used ASHP unit). In this paper, a comparative study on system performances of a multi-split ASHP unit under frosting condition with different energy accumulator structures and energy storage methods was experimentally carried out. The experimental results showed that the multi-ASHP unit employing fin-tube energy accumulator with serial energy storage method can achieve the longest heating period, which was 3.3%, 13.4%, and 9.4% longer than that employing spiral-tube energy accumulator with serial energy storage method, spiral-tube energy accumulator with parallel energy storage method, and fin-tube energy accumulator with parallel energy storage method, respectively. For spiral-tube energy accumulator using serial energy storage method, using parallel energy storage method, can shorten the energy storage period from 59 to 33 min. For fin-tube energy accumulator using serial energy storage method, using parallel energy storage method can shorten the energy storage period from 33 to 6 min. In addition, compared to serial energy storage method, using parallel energy storage method may significantly reduce the heating capacity, input power and heating COP of the multi-split ASHP unit during the energy storage period.