板式换热器Ni-P-TiO2复合纳米镀层微生物污垢特性

换热器微生物污垢问题普遍存在于能源化工领域，污垢的聚集会导致设备的流动阻力、燃料消耗和维护成本支出大幅度增加。本文采用复合纳米镀层来抑制和减轻换热表面的微生物污垢的附着和沉积。首先采用化学镀的方式，在板式换热器的不锈钢316板上镀覆 Ni-P-TiO₂复合纳米镀层和对照性的Ni-P 镀层。基于板式换热器的微生物污垢在线监测实验系统，研究了镀覆Ni-P-TiO₂复合纳米镀层的板式换热器微生物污垢特性。结果表明，清洁状态下，镀覆两种镀层的板式换热器其摩擦系数（f）和Nusselt数（Nu）相较未镀覆板式换热器均略有增加；微生物污垢实验后，相比较未镀覆的板式换热器，镀覆Ni-P镀层的板式换热器污垢热阻减少了8.36%~23.07%，而镀覆Ni-P-TiO₂复合纳米镀层的板式换热器污垢热阻减少了16.6%~30.96%；在相同微生物污垢实验工况下，镀覆Ni-P-TiO₂复合纳米镀层的板式换热器的摩擦系数（f）相比Ni-P镀层的低2.54%~11.82%，但Nu却明显高于Ni-P镀层达8.47%~9.45%，并且污垢热阻明显小于Ni-P镀层达10.66%~18.18%，镀覆Ni-P-TiO₂复合纳米镀层的板式换热器展现了优异的强化传热性能和抑垢性能。

Characteristics of microbial fouling on Ni-P- (nano) TiO2 composite coating of plate heat exchanger

The problem of microbial fouling of heat exchangers is common in the field of energy and chemical industry. The accumulation of fouling will lead to a substantial increase in the flow resistance, fuel consumption and maintenance cost of equipment. In this paper, a nano-composite coating was prepared to reduce the adhesion and deposition of microbial fouling on heat exchange surface. Firstly, the Ni-P- (nano) TiO₂ composite coatings and the controlled Ni-P coatings were prepared on stainless steel 316 plates of a plate heat exchanger by using electroless plating. Secondly, based on the heat exchanger microbial fouling on-line monitoring experimental system, the microbial fouling characteristics of plate heat exchangers coated Ni-P- (nano) TiO₂ composite coating were investigated experimentally. The results showed that the friction coefficient (f) and Nusselt number (Nu) of the two coated plate heat exchangers were a little higher than the uncoated one when it is in cleaning conditions. After the microbial fouling experiment, compared with the uncoated plate heat exchanger, the fouling resistance of Ni-P coated plate heat exchanger was reduced by 8.36%—23.07%, while the other one coated Ni-P- (nano) TiO₂ was reduced by 16.6%—30.96%. Under the same microbial fouling experimental conditions, the heat transfer and fouling characteristics of the two coatings were compared and analyzed further. The friction coefficient (f) of plate heat exchanger coated Ni-P- (nano) TiO₂ coating was reduced by 2.54%—11.82% compared with the coated Ni-P one, while Nu was increased by 8.47%—9.45%, and the fouling resistance was reduced by 10.66%—18.18% correspondingly. The plate heat exchanger coated Ni-P- (nano) TiO₂ composite coating showed an excellent microbial fouling inhibition performance in heat mass transfer process.