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Fabrication of Superhydrophobic Surfaces to Decrease Pressure Drop through the Galvanized Pipe and Study about Feasibility of the Fabricated Surface to Use for Non-newtonian Fluid

Pakzad, Hossein | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52147 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Mousavi, Ali; Nouri boroojerdi, Ali
  7. Abstract:
  8. Nowdays, one of the most important concerns for scientists is increasing CO2 emmisions and global warming. To overcome this problem, a large number of studies have been carried out to improve energy system performance and reducing the overall energy consumption. One solution to this problem is using the superhydrophobic surfaces with contact angle larger than 150°.In this study, we try to reduce the pressure drop through the galvanized pipes. So, by reducing the pressure drop, power required for pumps can be reduced. To this end, two different coatings by silica nano-particles which were modified with first hydrophobic agent are used. In first coating which is named as PS coating, stearic acid is used to modify hydrophobic silica nano-particles, whereas the second coating which is named as BWS coating, beeswax is used to improve the hydrophobicity of the hydrophobic silica nano-particles. It is notable that, epoxy resin with polyimide hardener is used so stabilize the nano particles on the surface.The contact angle of the first coating is 154.6°, whereas the contact angle of the second coating is 153.3°. these two coating possesse a sliding angle lower than 4°. Stability of the PS coating in underwater, silane, acidic and alkaline medium is better than the BWS coating. Therefore, its contact angle does not change a lot after immersing in such medium. It is notable that, the corrosion rate of these two coatings in 3.5% NaCl solution is so desirable with respect to the as received substrate. A 1in galvanized pipe coated by PS solution shows 24.62% decrease in pressure drop at Reynolds number of 20000, whereas a galvanized pipe with same dimensions coated by BWS solution shows 19.37% decrese in pressure drop at same Reynolds number.Aslo, these surfaces show fluid repellency to shear-thinning non-Newtonian fluid (1%,3%,5%,8% W/W CMS solutions in water). These surfaces show contact angle larger than 120° for this solutions
  9. Keywords:
  10. Conveying Flow ; Epoxy Resin ; Superhydrophobic Surfaces ; Pressure Drop Reduction ; Silica Nanoparticles ; Non-Newtonian Fluids ; Drag Force

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