Effects of solid particle surface roughness on particle velocity fluctuation in multi-zone waste heat recovery heat exchanger

Abstract

The velocity fluctuation affects the safe operation of the heat exchanger when the particles flow through the heat exchanger. The particle flow model of heat exchanger is established based on the discrete element method to investigate the correlation between surface roughness and particle velocity fluctuation. Many studies have used static friction coefficients to characterize the particle roughness. The particle velocity fluctuation in heat exchanger is analyzed, and the effects of the static friction coefficient on the particle velocity fluctuation are studied. The results showed that when the particles flow stably, the force chain structure between the particles is a process of breaking and rapidly reconstructing. This force characteristic of the particles causes the constant fluctuation of the particle velocity, which fluctuation frequency varies from 0.05 Hz to 0.08 Hz. The velocity fluctuations of the particles located at the top of the heat exchanger are particularly violent. The direction of the force chain distribution gradually moves horizontally with the increase of the static friction coefficient, and the velocity fluctuation in the vertical orientation becomes more intense. The amplitude of velocity fluctuation increases from 0.6 × 10−3 m/s to 1.3 × 10−3 m/s. The results are helpful to understand the dynamic behavior of particle in heat exchanger during flow and provide the basis for subsequent improvements.