Deaeration theory

Since these experiments were not carried out under ideally defined flow conditions the dependence of corrosion rate on flow rate will be discussed only in a qualitative manner. Under laminar flow conditions and mass transfer control one would have expected the corrosion rate to increase with the square root of the velocity while under turbulent conditions proportionality would prevail. However, in Fig.15 one finds that the corrosion rate varies approximately with the 0.2 to 0.3 power of the flow rate. It appears therefore that the observed dependence on the flow rate does not obey conventional mass transfer theory. A flow effect might be expected in uninhibited hydrochloric acid because hydrogen bubbles, formed on the surface of the metal, are faster and more easily removed at higher flow rates. While this argument could be applied in discussing Fig.15, we find in Fig.16 that the flow effect at similar corrosion rates is much less pronounced under deaerated conditions. We therefore have to conclude that the observed flow effect is not mechanical and cannot be related to pure mass transfer control either. In Fig.17, the flow dependence of the corrosion rate is shown for 2-butyne-l,4-diol in deaerated UN hydrochloric acid. Note that the corrosion rate appears to be noticeably affected only at the higher flow rates. Finally, in Fig.18, we observe that increased flow rate can either increase or decrease the corrosion rate in the presence of an inhibitor. This effect was observed reproducibly only in 6N hydrochloric acid with 2-butyne-l,U-diol under deaerated conditions for 0.2% and 0.1% inhibitor concentration. This behavior indicates that the corrosion rate is controlled by the superposition of two partial reaction rates each of which is mass transfer dependent to a certain extent. In terms of the model delineated in Table 6, it is suggested that the three-dimensional polymeric layer made up by inhibitor molecules is in fact a three-dimensional chelate made up of iron ions and inhibitor molecules. The corrosion rate is then... 

McGeorge, H. D. Marine Auxiliary Machinery. 7th ed. Burlington, Mass. Butterworth-Heinemann, 1995. Excellent descriptions of shell-and-tube heat exchangers, plate heat exchangers, and deaerators are provided in very readable form, including a simple presentation of heat exchanger theory. 

FIG. 12—Anodic polarization diagrams of pitch-based graphite fiber (cross section exposed), monolithic 6061-T6 aluminum, and Gr(50 vol. %)/6061-T6 Al MMC plate exposed to deaerated 0.5 M Na2S04 at 30°C. Scan rate = 0.1 mV/s. A diagram for a composite consisting of 50 vol. % graphite and 6061-T6 aluminum was generated on the basis of the mixed-potential theory. 

Design Theory, Simplified Design Procedures, Column Diameter Selection, Water Deaeration, Water Decarbonation, Ammonia Stripping, Amine Regeneration, Hot Carbonate Regeneration, Side Strippers, Example Problem, Notation, References... 

The popularity of the RRDE technique results from several considerations [11] An adequate theory has been available for a long time, the RRDE has the advantage of well-controlled hydrodynamics and the rate of mass transport can be varied easily by varying the rotation rate, the electrodes can be easily cleaned and polished, the RRDE is placed in a recipient that can easily be deaerated and thermostated. 

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