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Behaviour of superhydrophobic, hydrophobic and hybrid surfaces in condensation heat transfer application
Author(s): Hassan Davar, N. M. Nouri, Mahdi Navidbakhsh
Keywords: Dropwise condensation; Heat transfer coefficient; Heat flux; Hybrid hydrophobic-hydrophilic surface.
The effects of different hydrophobic and superhydrophobic coatings were investigated on the heat transfer coefficient and contact angle of the plates, and compared to the non-coated surface. The initial investigation showed that the plate with the commercial coating Danphobix offered the formation of better condensate droplets -in comparison to other coatings- on which dropwise condensation occurred. Then, the plates with the commercial coating Danphobix were investigated at five different thicknesses to enhance the heat transfer coefficient. According to the obtained results, decreasing the initial thickness of coating to a definite value, the heat transfer coefficient was augmented. By further decrease, the heat transfer coefficient was reduced due to the elimination of the physical structures of the coating against steam. Different coating combinations were examined according to Energy Dispersive X-Ray and Scanning Electron Microscopy analysis, showing that the commercial coating Danphobix formed a hydrophilic-hydrophobic hybrid surface due to the particular properties generated after the surface coating as well as the specific features of the hydrophilic aluminum substrate. In what follows, in addition to the critical thickness, the critical area of the coated surface is also obtained.