Effect On Ni-P-TiO₂ Modified Surface On Particles Fouling Deposition Characteristics Of Piate Heat Exchanger

The accumulation of particles fouling in the heat exchanger causes a number of problems such as fuel consumption,resulting in increased flow resistance and maintenance cost expenditures.There are still very limited the methods to deal with particles fouling in heat exchange equipment.The development of surface technology provides new ideas to inhibit the accumulation of particles fouling in heat exchange equipment.In this paper,Ni-P-TiO₂composite nano-modified surface was prepared on 316 stainless steel with the size of（30×30×0.2）mm³ by chemical composite plating method,and the properties of the surface were analyzed.At room temperature,MgO with particle size of 50nm and concentration of 1g/L was added into the cooling water to simulate the granular fouling medium,and the Ni-P-TiO₂ composite nano-modified surface MgO particle fouling experiment was carried out.In the static experiment,the relationship between the fouling adhesion and Ni-P-TiO₂ composite nano-modified surface was obtained under different process parameters.The surface energy of the Ni-P-TiO₂ composite nano-modified surface was measured by contact angle taster.Combined with the static experimental results and based on the extended DLVO theory,the optimal total surface energyγ^TOT which can minimal the adsorption and accumulation of particle fouling was obtained.In the dynamic experiments,the heat transfer characteristics and MgO particle fouling characteristics of the plate heat exchanger coated with Ni-P-TiO₂ composite nano-modified surface were studied by using the experimental platform which can monitor the particle fouling growth in real time.The results show that the total heat transfer coefficient of the Ni-P-TiO₂composite nano-modified surface is reduced by 9.63%～10.5%compared with that of the 316stainless steel heat transfer surface at different flow rates in the clean water experiment;At different temperatures,the total heat transfer coefficient of the Ni-P-TiO₂ composite nano-modified surface is reduced by 9.72%～12.01%compared with that of the 316 stainless steel heat transfer surface;After the MgO particle fouling experiment,when the inlet flow rate of low-temperature circulating medium is 0.1m/s,0.2m/s and 0.3m/s,the fouling thermal resistance of Ni-P-TiO₂ composite nano-modified surface is reduced by 27.85%,22.54%and 34.41%compared with 316 stainless steel,respectively;When the inlet temperature of low-temperature circulating medium is 30℃,35℃and 40℃,respectively,the fouling thermal resistance of Ni-P-Ti O2 composite nano-modified surface decreases by 25.15%,33.18%and 39.14%compared with that of 316 stainless steel,respectively;When the concentration of MgO nanoparticles is 100mg/L,200mg/L and 400mg/L,respectively,the fouling thermal resistance of Ni-P-TiO₂ composite nano-modified surface decreases by 26.15%,24.98%and 45.36%compared with that of 316 stainless steel,respectively.Combined with the calculated of surface free energy,the surface free energy of the Ni-P-TiO₂ composite nano-modified surface is less than that of the 316 stainless steel surface.Therefore,the fouling thermal resistance of MgO nanoparticles obtained in this experiment decreases with the decrease of surface free energy,which is consistent with the results of the shows static experiment.It is advisable to sacrifice a small of heat transfer coefficient in exchange for the service life of the heat exchanger.The plate heat exchanger coated with Ni-P-TiO₂ composite nano-coating shows excellent scale inhibition performance.