Superhydrophobic Properties Of Stearic Acid Wet-Modified Stainless Steel And Its Heat Transfer Properties In Dusty Moist Air

In various industrial production,a large amount of industrial waste heat is generated.If this energy is not recovered and utilized,but dissipated in the ambient air,it will cause a lot of energy waste and reduce the energy utilization efficiency.Sludge drying exhaust gas contains a large amount of sensible and latent heat,and it is of great value to recover this energy by using heat recovery technology.Since the sludge drying exhaust gas contains a large amount of dust,this dust will easily adhere to the inner surface of the heat exchanger,resulting in unnecessary fouling and thermal resistance,thus reducing the heat exchange effect,which can seriously lead to blockage of the heat exchange pipeline,causing equipment downtime and increasing operating costs.To solve this problem,superhydrophobic materials have low adhesion and self-cleaning properties,and their surfaces can be easily carried away by water droplets at a certain inclination,thus reducing dirt adhesion to the heat exchanger surface,which is expected to solve the above problem.A green,low-cost,and time-saving process was proposed to prepare a superhydrophobic stainless steel surface,using dilute aqua regia and hydrogen peroxide solutions to construct rough micro-nanostructures on the stainless steel surface,followed by a low-cost fluorine-free stearic acid modification treatment to green and easily achieve a superhydrophobic surface with a water contact angle of up to 158.3°and a sliding angle of 2.3°on 304 stainless steel.In order to obtain a good rough structure and low surface energy for optimal superhydrophobicity.The effect of different etching parameters and modification parameters on the wettability of the stainless steel surface was investigated.The best superhydrophobicity was obtained at an etching time of 30 min,a molar ratio of H⁺to H₂O₂ of 1/0.4,a stearic acid concentration of 0.03mol/L,a modification time of 3 h,and a modification temperature of 70°C.The mechanism was characterized using field emission scanning electron microscopy（FESEM）,X-ray photoelectron spectroscopy（XPS）,and Fourier transform infrared spectroscopy（FTIR）.Various tests were performed on the properties of the prepared superhydrophobic stainless steel surfaces in order to better meet practical industrial applications.The results of durability,wear resistance,corrosion resistance,and thermal stability tests showed that the prepared superhydrophobic stainless steel surfaces have good durability,wear resistance,corrosion resistance,and thermal stability.This superhydrophobic material with good water repellency,durability,wear resistance,corrosion resistance,and high heat resistance has many potential applications in various industrial applications.The superhydrophobic stainless steel tube was prepared by the above method and applied to the heat transfer inner tube of the water-cooled jacket,and its heat transfer and fouling conditions under different moist air conditions were studied.The heat transfer coefficient of superhydrophobic stainless steel tubes is significantly higher than that of ordinary stainless steel tubes under dust-free and dusty working conditions with different Reynolds number Re.Under different heat transfer gas temperature conditions,the heat transfer coefficient of ordinary stainless steel tube and superhydrophobic stainless steel tube is increased with the increase in the temperature of the heat transfer gas,and the heat transfer coefficient of superhydrophobic stainless steel tube is always greater than that of ordinary stainless steel tube.Under different dust concentration conditions,the heat transfer coefficients of ordinary stainless steel tubes and super-hydrophobic stainless steel tubes decrease with the increase of dust concentration,and the heat transfer coefficient of super-hydrophobic stainless steel tubes is significantly larger than that of ordinary tubes,and the dust adhesion amount decreased.It shows that superhydrophobic materials have potential advantages in reducing fouling and enhancing the heat transfer effect.