Graduate Thesis Or Dissertation

 

Fouling characteristics of cooling tower water containing corrosion inhibitors Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/n583z0134

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  • The fouling characteristics of cooling tower water containing various corrosion inhibitors and other additives on heat transfer surface have been investigated. Corrosion inhibitors investigated included zinc-chromate and phosphates. In addition, additives including polyacrylate and phosphonate (HEDP and AMP) were used to determine their effectiveness as antifoulants. The tests were conducted in a simulated cooling tower water system. The parameters investigated were: test section surface temperature 130, 145 and 160 °F, velocity in test section 3.0, 5.5 and 8.5 ft/sec, pH 6.0 - 8.0, and material of the fouling surface (stainless steel, carbon steel, 90/10 copper/nickel, and admiralty brass). The water bulk temperature in all tests was 1150F. The water had a total hardness of 800-1000 ppm as CaCO₃, total sulfate of 800-1000 ppm as SO₄ and silica of 40-45 ppm as SiO₂. For each test, a fouling resistance time curve was obtained. This curve was fitted to the equation Rf = Rf* (1- exp(-(0-ed)/0c)) to yield the values of 0c and Rf*. Rf is the fouling resistance predicted by the regression equation, Rf* is the asymptotic fouling resistance, 0 is time, ed is dead time and 0c is the time constant for the asymptotic decay. The values of 0c and Rf* from regression analysis have been correlated with the various parameters by the Heat Transfer Research, Inc., (HTRI) fouling model. For the range of conditions studied, the correlation equations 7-1 to 7-4 relate the fouling resistance, Rfj to the surface temperature, wall shear stress and water quality. Seventeen different water qualities were investigated to determine the values of 5 parameters, which are specific for each water quality. For each of the seventeen water qualities studied threshold curves for three threshold values of Rf* have been developed as a function of velocity and surface temperature. These curves are useful to obtain the conditions required to maintain a desired value of Rf* in a heat exchanger.
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