Condensers, air-side fouling, washing, flow resistance, heat transfer
Air cooled condensers are commonly used in rooftop units and residential air-conditioners to reject heat outdoors. Airborne particles in the environment, such as dust, grass, leaves, seeds, and anthropogenic agents, can foul the air side of the condensers. Therefore, it is common practice to regularly clean the air side of condensers. Seven fouled wavy fin, and two fouled spiny fin condensers from residential condensing units were collected at the end of their service lives, and examined in the laboratory to study the effect of the fouling on heat transfer capacity and air-side flow resistance. A test apparatus was designed and built to investigate the flow resistance and heat transfer of these coils before and after cleaning. After testing each condenser in the fouled condition, the fouling material was collected and its mass was measured. Then, the coil was washed with water and tested again in the test apparatus. Finally, to investigate the effectiveness of commercial detergents, these coils were cleaned with a detergent and tested again. Surprisingly, the results show that the effect of washing on the heat transfer capacity of the coil is very small, and in some cases, the fouled condenser performed better before cleaning than afterwards. Similarly, cleaning the units with detergent had negligible differences compared with the effects from cleaning with water only, and in some cases, the detergent caused performance degradation in terms of flow resistance and heat transfer.