Browsing by Author "Goodenough, J. L."

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    The effects of paint-based protective films on the actual temporal water-side performance characteristics of steam surface condenser tubes.
    (2017-03) Goodenough, J. L.; Reuter, H. C. R.; Owen, Michael ; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Paint-based protective films (PPFs) are applied to the internal surface of steam surface condenser tubes to mitigate corrosion and erosion. The performance impact resulting from fresh-water fouling on these PPFs is experimentally investigated using actual cooling water from a thermal coal-fired power station. Four different paint types are tested alongside unmodified stainless steel, titanium, and brass tubes for direct comparison, using a purpose-built test apparatus featuring six co-current flow double-pipe heat exchangers arranged in parallel. Exposure times vary between 85 days and 280 days providing novel information pertaining to these PPFs in terms of their performance over time. Cooling water exiting the condenser is drawn from a take-off valve fitted before the cooling duct enters thewet-cooled cooling tower, and passes through the test apparatus at 4 L/s. The cooling water passes once through each test tube at the condenser design velocity before being returned to the cooling tower pond. Each tube is heated using water instead of steam, to provide consistent and repeatable outer convection conditions. By measuring a total of 24 bulk fluid temperatures and 12 volumetric flow rates, the heat transfer, and hence fouling factor, for each tube is determined during tests. In order of decreasing predominance: biological fouling, precipitation fouling (scaling), and particulate fouling (deposition) are identified on all the test tubes. The unmodified admiralty brass tube provides the best overall performance because its copper ions retard the biological fouling rate. The non-biocidal PPFs experience similar fouling to all the non-copper alloy tubes tested, where their asymptotic fouling factors are almost five times greater than the copperbearing alloy tested. The data gained using the testing techniques described herein allows the dominant fouling mechanism to be identified and can be used to better design water treatment management, as well as direct further PPF development towards reducing biological fouling tendencies. One of the biocidal PPFs that is tested reaches a lower fouling factor than an unmodified stainless steel tube after 85 days of exposure under the same conditions. These results are compared to the plant’s condenser fouling factor, calculated using a one dimensional condenser model. The agreement between the fouling factor measured on single tubes compared to the fouling factor of the condenser validates the testing and further means that the fouling data can be used to enhance condenser design and management using PPFs.