A novel defouling initiation method for a space cooling ASHP unit based on its measurable characteristic ambient and operating temperatures. (August 2019) - Li, Zhaoyang
Highlights: A novel method for defouling fouled outdoor coils in ASHPs has been developed. The method is based on three directly measurable operating temperatures. Further field studies to verify the method's applicability were carried out. The method provided an accurate and convenient way for defouling initiation. Abstract: Air source heat pumps (ASHPs) have been widely used for space cooling in recent years. When a space cooling ASHP unit is operated in an ambience with poor air quality, fouling of its outdoor coil can be easily built up, leading to a significant drop in the operating efficiency and output cooling capacity of the ASHP unit. Therefore, as a follow-up to a previous related study, a study to develop a novel defouling initiation method for the fouled outdoor coil in a space cooling ASHP unit based on its measurable characteristic ambient and operating temperatures has been carried out and the study results are reported in this paper. Firstly, a characteristic parameter of TTT, which can be evaluated based on ambient air Temperature, outdoor coil metal surface Temperature and outdoor coil outlet air Temperature, is defined. Secondly, the development of the novel defouling initiation method is detailed. Finally, further field comparative studies using the developed novel defouling initiation method have been carried out, and the study results demonstrated that the novel defouling initiation method can provide an accurate and convenient way to initiate defouling of the fouled outdoor coil in an ASHP unit at a reasonable defouling frequency to ensure its best possible operating performances.