Numerical study on formation characteristics of particle-crystal mixed fouling in the heat exchanger tube

Abstract

A mixed fouling prediction model is developed to investigate the problem of heat exchanger fouling in cooling water systems, which considers the particle-crystal mixed fouling deposition and evolution processes. As the fouling thickness exceeds the fluid cell height, the fluid cell is converted into a porous media cell to represent the fluid flow in the fouling layer. The mixed fouling layer growth and evolution are simulated using the porous media model and a user-defined program. The fouling resistance obtained from the model agrees well with the experimental data in the literature. Additionally, the fouling thickness distribution on heat transfer surfaces is predicted. The differences between mixed fouling and single fouling are compared. Then the effect of fluid parameter variations on fouling characteristics is investigated within the heat exchange channel. The results show that fouling accumulates at the end of the pipe, exhibiting a distribution trend of being thin at the front and thick at the back. Moreover, the risk of fouling formation significantly increases with increasing inlet temperature, concentration and heat flux, while high inlet velocity leads to small fouling resistance. The asymptotic value of fouling resistance decreases by 59.1% when the inlet velocity increases from 0.25 to 0.65 m/s.