The mal-defrosting phenomenon occurs frequently when the air source heat pump (ASHP) is defrosting

which causes a decline in the heating capacity

performance

and heating loss. Therefore

it is crucial to determine the most appropriate start and end times. To control the start and end time of defrosting properly

the ASHP has a state of stable performance and energy saving and can ensure thermal comfort in the room during defrosting. In this study

the research on defrosting control methods at home and abroad are summarized

and the limitations of defrosting control methods are analyzed

including measuring the frost thickness directly

monitoring the frost degree indirectly

and determining the start and end times using an intelligent algorithm. The idea of a combination of frost suppression technology and a defrosting control method

the relationship between the type of equipment and defrosting control method

as well as an evaluation system for defrosting control methods were put forward as the future research direction in this paper.