Numerical model of particle deposition on wet fin surfaces of heat exchanger under dehumidifying conditions

Abstract

Dusty particles may easily deposit on fin surfaces of heat exchangers under dehumidifying conditions and thus seriously deteriorate the heat transfer performance. The purpose of this study is to develop a numerical model for simulating the dusty particle deposition on wet fin surfaces in practical working processes, including the shape and mass of the deposited dusty particles in the process of particle-capturing by condensate water and that of particle adhesion on wet particulate layer. The prediction method of the dusty particle deposition in the process of particle-capturing by condensate water is to simulate the motion trajectories of all particles in the air flow at first and then to choose those particles intersecting with the water surface as deposited. The prediction method of the dusty particle deposition in the process of particle adhesion on wet particulate layer is to calculate the critical sticking velocity at first and then to choose those particles with the impact velocity being smaller than the critical sticking velocity as deposited. The validation results show that, the predicted shape of wet particulate layer agrees well with the experimental images, and the predicted mass of deposited particles agrees with 91% of the experimental data within a deviation of ±20% and the mean deviation is 11.8%. Prediction results of the quantitative influence of operation conditions with this model show that the parameters of inlet air relative humidity and particle concentration are the two most important factors on dusty particle deposition on wet fin surfaces.