Simulation of ash deposition in different furnace temperature with a 2D dynamic mesh model

Ash deposit on the heat exchangers reduces the heat transfer efficiency and even threatens the operation of the equipment. The tool of computational fluid dynamics (CFD) allows for better understanding of the deposit formation and the prediction of the process. This paper presents an improved CFD model to reproduce the growth of ash deposition on a temperature-controlled probe in a pilot-scale furnace with the commercial software Fluent16.0. Dynamic mesh technique is included to investigate the shape variation of the ash deposit during the deposit growth. The model is improved by taking the changing surface temperature of the deposition into consideration. The deposition efficiency, surface temperature and heat flux through the deposit are monitored as the iteration. Three cases are presented to investigate the influence of furnace temperature (1473 K, 1523 K and 1573 K). The results show that the deposition efficiency increases with the increasing surface temperature of the deposit while the mass flow of impaction decreases with the changing flow field. The growth rates of the deposit for the three cases are 0.064, 0.079 and 0.103 mm/min within the simulation time which is consistent with experiment results. The simulated surface temperature shows the same trend of the experimental values. The heat flux in the simulation decreases with a range of 38.2%, 50.3% and 50% for the three cases, respectively. This method of modelling can be used to predict the growth of deposit accurately.