Material Behavior of Hydrophobic Yb2O3 and Photocatalytic TiO2 Coatings in HVAC Water Cooling Towers: A Case Study

An HVAC water cooling tower utilizes water in the heat transfer process. Occupational Safety and Health Administration (OSHA) mandates that HVAC systems must be cleaned twice a year to prevent pneumatic diseases, which is a costly process. In this work, hydrophobic coatings of Yb2O3, and coatings of TiO2 and TiO2+Cu are tested as potential coatings for water cooling towers. The samples were placed in water splash zones to ensure exposure to sufficient water effects. The samples were placed for 6 months in. One sample of each set was placed in the shade, while another sample was placed in sunlight to examine the different effects. For the TiO2, all samples were placed in sun-exposed areas. During the test, the sample with the prime coating of YSZ and top coating of 50 μm Yb2O3 exhibited the best behavior compared with the rest of the samples coated with bond coating of Cr2O3. As expected, sunlight adversely affected all samples, with an increase in the number of locations with dark stains due to algae formation. In addition, the top coating of Yb2O3 improved the result. For the TiO2 coating, the addition of copper rendered better results, whereas low concentrations of several elements, such as slats, are observed in the samples with the added copper. The results are in a preliminary stage, and a complete antimicrobial analysis is needed.