Operating performances of a space heating ASHP unit with a foul outdoor coil following a prolonged cooling operation

Fouling and frosting of the outdoor coil in an air source heat pump (ASHP) unit are common but undesirable operating problems. At an increased level of air pollution, fouling of an outdoor coil becomes increasingly severe during its space cooling operation in summer and may potentially impact its frosting operation in winter. This paper reports on a field study on the operating performances of a space heating ASHP unit with a foul outdoor coil as a result of a prolonged cooling operation. Firstly, a detailed description of the field ASHP unit with the foul outdoor coil and test cases is given. Secondly, field study results for the test cases and their analyses are presented. The results demonstrate that fouling of an outdoor coil during its space cooling operation in summer can significantly impact its frosting performance during its space heating operation in winter.