Research On The Fouling Properties And Model Of Nano-composite Surfaces In Plate Heat Exchanger

In the development and application of heat exchange equipment with excellent performance,fouling is a high-hazard,common and very difficult problem.Especially for equipment with high heat exchange efficiency and compact structure,such as plate heat exchangers,the fouling problem is even more troublesome.Effective treatment of fouling problems is of great significance for achieving"carbon peak and carbon neutrality".The nano-composite surface of the heat exchanger is an effective method to inhibit the growth of fouling.In this study,the stainless steel 304 heat exchange plate is used as the base,combined with nanoparticles of different properties,to obtain the corresponding nano-composite coatings.Using a combination of experimental and theoretical analysis methods to explore the characteristics of fouling growth on heat exchange surfaces,and analyze fouling properties and fouling models on different surfaces.The main research content and methods of this article are as follows:（1）The Ni-P-PTFE and Ni-P-TiO₂nano-composite coatings were prepared on the stainless steel 304 plate heat exchanger plates by chemical composite plating method,and the surface structure,contact angle and surface energy of the three heat exchange surfaces were characterized.Compared with stainless steel 304,the Ni-P-PTFE and Ni-P-TiO₂ coatings have lower surface energy.（2）Heat exchange experiments were carried out on PHEs with three heat exchange surfaces of stainless steel 304,Ni-P-PTFE and Ni-P-TiO₂ at different flow rates.Compare and analyze the pressure drop and heat transfer coefficient of different heat exchange surfaces,and explore the influence of nano-composite surface and flow velocity on the heat transfer coefficient and pressure drop of PHEs.The results show that the two modified surfaces have little effect on the heat transfer performance of the heat exchanger,but both reduce its flow resistance.（3）Use numerical calculation to observe the temperature and flow velocity distribution in the PHE.The PHE has a large heat exchange temperature difference and a small end temperature difference,reflecting good heat exchange performance.The velocity of the fluid decreases slightly as it flows from the distribution area to the heat transfer area because it experiences more resistance than in the distribution area.（4）Accelerated fouling tests were carried out on PHEs with three different surfaces.Analyze the heat and mass transfer characteristics in the process of fouling growth,observe the microscopic morphology of fouling,and explore the anti-fouling performance of Ni-P-PTFE and Ni-P-TiO₂ nano-composite coatings.The Ni-P-PTFE and Ni-P-TiO₂ surfaces reduced the fouling thermal resistance of the PHE by 28.2%and 25.6%,respectively,showing excellent anti-fouling performance.（5）According to the experimental data,combined with the Von-Karman analogy and the Kern-Seaton fouling model,the influencing factors in the fouling process including mass transfer coefficient,friction factor,fouling bond strength and adhesion probability are theoretically analyzed.Among them,compared with stainless steel 304,Ni-P-TiO₂ and Ni-P-PTFE surfaces reduced the fouling bond strength by 42.1%and 30.5%,respectively.It is believed that the reduction of fouling bond strength is one of the main reasons for the excellent anti-fouling properties of the two nano-composite surfaces.The research results of this paper provide directions for the design and application of heat exchangers in industrial production,and accumulate fouling research data.At the same time,the paper has accumulated a certain amount of experience for the anti-fouling and anti-corrosion research of plate heat exchangers.