Real-time fouling characteristics of a typical heat exchanger used in the waste heat recovery systems

A numerical method was developed to investigate the fouling characteristics of a typical heat exchanger. Firstly, an integrated fouling model which consists of a deposition process and a removal process was developed to simulate the fouling characteristics. The deposition criterion was determined by the energy balance during the interaction of particle and surface, and the removal process was based on the local wall shear stress and the fouling thickness. Then, the fluid flow characteristics were calculated and the discrete phase model (DPM) was employed to trace the fly ash particles during the fouling process. Since the simulation time is much smaller in magnitude than the real time in fouling process, a fouling time ratio was proposed to enlarge the simulation time and results to the real time scale. The flow characteristics, real-time fouling characteristics and the effects of inlet velocity, particle diameter on the fouling resistance were investigated. At last, the comparison with experimental results was also conducted. The results show that the particle motion was easily controlled by different vortex structures and the fouling mainly occurred in the flow stagnation region and the recirculation region. The net fouling results shows an asymptotic characteristic of growth and the increase in inlet velocity and particle diameter would lead to a decrease in fouling results.