Abstract
As the heat transfer surface in the passive containment cooling system, the anticorrosion coating (AC) of steel containment vessel (CV) must meet the requirements on heat transfer performance. One of the wall surface ACs with simple structure, high mechanical strength, and well hydrophobic characteristics, which is conductive to form dropwise condensation, is significant for the heat removal of the CV. In this paper, the grooved structures on silicon wafers by lithographic methods are systematically prepared to investigate the effects of microstructures on the hydrophobic property of the surfaces. The results show that the hydrophobicity is dramatically improved in comparison with the conventional Wenzel and Cassie-Baxter model. In addition, the experimental results are successfully explained by the interface state effect. As a consequence, it is indicated that favorable hydrophobicity can be obtained even if the surface is with lower roughness and without any chemical modifications, which provides feasible solutions for improving the heat transfer performance of CV.
Highlights
The advanced pressurized water reactor [1] adopts a passive containment cooling system [2, 3] (PCCS) relying on heat removal by condensation to maintain the steel containment vessel (CV) within the design limits of pressure and temperature, which effectively prevents the leakage of radioactive materials under accident situations
Heat transfer coefficients for dropwise condensation of steam are greater with one to two orders of magnitude [5,6,7,8,9], which can effectively enhance the ability of heat transfer on CV, while dropwise condensation takes place on a hydrophobic surface where the contact angle is usually larger than 90 degrees, whose heat transfer rate increased with the increase in the contact angle [10]
The results demonstrate that outstanding hydrophobic performance can be Science and Technology of Nuclear Installations obtained by microstructure engineering without any chemical modifications; the mechanism of hydrophobic enhancement is described and discussed as well
Summary
The advanced pressurized water reactor [1] adopts a passive containment cooling system [2, 3] (PCCS) relying on heat removal by condensation to maintain the steel containment vessel (CV) within the design limits of pressure and temperature, which effectively prevents the leakage of radioactive materials under accident situations. As the condensation surface in PCCS, the safety-related anticorrosion coating (AC) of CV must meet the requirements of heat removal capacity. The thermal conductivity of current applicative coating on CV is about 1.0 Wm−1K−1; besides the thickness of the coating is in the range of 50–150 μm, which results in high thermal resistance. The contact angle of the coating is lower than 30∘; such high wettability results in filmwise condensation [4]. For further improving the running safety of the existing or future highpower nuclear power plant, the lower thermal resistance, simple structure, excellent physical and chemical stability, and optimized hydrophobic surface are highly in demand for the safety margin of CV
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