Fouling on the heat transfer surfaces of industrial heat exchangers is an intractable problem, and several techniques have been suggested to inhibit fouling. Surface coatings are of such techniques by which the adhesion force between fouling and heat transfer surface can be reduced with low surface free energy thin films. In this article, liquid phase deposition was applied to coat titanium dioxide thin films on the red copper substrates with film thickness in micro-or nano-meter scale. Coating thickness, contact angle, roughness, surface topography, and components were measured with X-ray diffraction, contact angle analyzer, stylus roughmeter, scanning electron microscopy, and energy dispersive X-ray spectroscopy, respectively. Surface free energy of coating layers was calculated based on the contact angle. Heat transfer and fouling characteristics in pool boiling of distilled water and calcium carbonate solution on coated surfaces were investigated. Heat transfer enhancement was observed on coated surfaces compared with untreated or polished surfaces due to the micro-and nano-structured surfaces which may increase the number of nucleation sites. The nonfouling time on the coated surfaces is extended than that on the untreated or polished surfaces due to the reducing of the surface free energy of coated surfaces. Corrosion behavior of coated surfaces soaked in the corrosive media of hydrochloric acid, sodium hydroxide alkali, and sodium chloride salt solutions with high concentration at room temperature a few hours was also explored qualitatively. Anticorrosion results of the coated surfaces were obtained. The coatings resisted alkali corrosion within 7.2 Â 10 5 s, acidic corrosion within 3.6 Â 10 5 s and salt corrosion within 2.16 Â 10 6 s. The present work may open a new coating route to avoid fouling deposition and corrosion on the heat transfer surfaces of industry evaporators, which is very important for energy saving in the related industries.

Underwater superoleophobic Ti6Al4V surfaces were fabricated successfully via electrochemical etching. The morphologies, chemical compositions and crystal structures of the prepared titanium alloy surfaces were characterised by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction, respectively. The relationship between the etching time and oil wettability in water was investigated and the formation mechanism of hierarchical micro/nano rough structures on titanium alloy surfaces was also carefully analysed. Further, a series of exposure, immersion and abrasion tests were conducted to evaluate durability, corrosion resistance and abrasion resistance of the fabricated titanium alloy surfaces under harsh conditions. The results show that the prepared surfaces exhibit good underwater superoleophobicity, whose oil contact angle for dichloromethane in water is 158.9°± 1.7°and corresponding sliding angle is 6.4°± 1.4°. Our approach is simple, efficient and may broaden the potential applications of superoleophobic titanium alloy surfaces in underwater self-cleaning and anti-oil pollution fields.

Micro-fabrication techniques are developed rapidly because they offer numerous benefits for chemical and biological industries. Numerical simulations (based on incompressible Navier–Stokes equations) are presented of the two-phase flow in a cross-flowing T-junction micro-channel using the phase field method and the results are in agreement with experimental measurements. The leakage rate in the gap between the droplet and lower wall decreases during the droplet formation, the relationship between the leakage rate and the derivative of the up-stream droplet size is obtained, which is applicable when the droplet contacts with the lower wall on the wetted conditions or expands to the up-stream in the main channel. The droplet formation is related to several factors, including the capillary number, the contact angle, the flow rate ratio, and the micro-channel shape. The critical capillary number could distinguish between the squeezing and dripping regimes for the generation of different kinds of droplets. The simulations show that the critical capillary number is 0.012. Influence of those factors on the droplet length is related to the leakage rate. The leakage rate of the continuous phase decreases slowly as the flow rate ratio decreases or contact angle increases. In the squeezing regime, the leakage rate is weakly influenced by the contact angle at the small flow rate ratio and is different in three type micro-channels, the droplet length increases with the increase in contact angle which intensifies growth at the big flow rate ratio, and the longest droplet is obtained in the Y-junction micro-channel. In the dripping regime, at the big flow rate ratio the leakage rate is almost independent to the contact angle and micro-channel shape, and the droplet length also is same.

Free energy variations with contact angle.