An experimental study was conducted to investigate the impacts of air-side fouling and cleaning on the performance of various condenser coils used in unitary air-conditioning systems. A total of six condenser coils with different fin geometries and depths were tested. Performance tests were conducted at three different conditions: clean-as-received, after fouling, and after cleaning.

In all cases, it was observed that fouling was mostly confined to the frontal face of the heat exchanger as reported in previous investigations. The amount of deposited dust was more dependent on fin geometry for single-row heat exchangers than for double-row heat exchangers. The predominant effect of fouling was to cause a more significant increase in air-side pressure drop than degradation in heat transfer performance. For the single-row heat exchangers, the pressure drop increased by 28% to 31%, while the heat transfer performance decreased by 7% to 12% at the standard air face velocity of 1.53 m/s depending on fin shape. For the double-row heat exchangers, the pressure drop increased by 22% to 37%, and heat transfer performance decreased by only 4% to 5% at the same air face velocity.

Once the contaminated coils were cleaned according to a manufacturer-specified cleaning procedure, the original performance of the heat exchangers was recovered almost completely. The pressure drop was restored to within 1% to 7% and the heat transfer performance could be recovered to within 1% to 5% of the originally clean heat exchangers. Therefore, it is concluded that a periodic application of specified cleaning procedures will be effective in maintaining the thermal performance of condenser coils.

Units: Dual