Developing a novel control strategy for frosting suppression based on condensing-frosting performance maps for variable speed air source heat pumps

Effective frosting suppression was crucial to further wider applications of air source heat pumps (ASHPs). However, existing frosting suppression measures may not be fully implementable in practice due to various reasons such as short service life, complex manufacturing process and high costs. A condensing-frosting performance map was obtained in a previous study to enable a comprehensive evaluation of the frosting suppression and heating performances of a variable speed (VS) ASHP unit. Therefore, the maps could also provide a basis for developing a novel control strategy for frosting suppression, while still meeting the requirement of desired output heating capacity. As a result, an experimental study on developing a novel control strategy based on the condensing-frosting performance maps has been carried out using an experimental VS ASHP unit, and the study results are presented in this paper. The experimental results suggested that the experimental VS ASHP unit under the proposed novel control strategy could not only achieve effective frosting suppression, but also output the required heating capacity at high COP values whenever possible. By using the developed novel control strategy, the heating duration in one cycle could be increased by up to 157.68 %, and the daily defrosting frequency, duration and energy consumption reduced by up to 59.09 %, 36.30 % and 32.96 %, respectively. The proposed novel control strategy was straightforward and simple to implement, and could contribute to the further development of frosting suppression for ASHPs.