Abstract
The effects of triboelectricity in a small-scale fluidized bed of polyethylene particles were investigated by imaging the particle layer in the vicinity of the column wall and by measuring the pressure drop across the bed. The average charge on the particles was altered by changing the relative humidity of the gas. A triboelectric charging model coupled with a computational fluid dynamics–discrete element method (CFD-DEM) model was utilized to simulate gas–particle flow in the bed. The electrostatic forces were evaluated based on a particle–particle particle–mesh method, accounting for the surface charge on the insulating walls. It was found that simulations with fixed and uniform charge distribution among the particles capture remarkably well both the agglomeration of the particles on the wall and the associated decrease in the pressure drop across the bed. With a dynamic tribocharging model, the charging rate had to be accelerated to render the computations affordable. Such simulations with an artificial acceleration significantly over-predict charge segregation and the wall becomes rapidly sheeted with a single layer of strongly charged particles.
Highlights
When two solid surfaces are brought into contact and separated, a net charge transfer may occur between the surfaces
We investigated the wall sheeting indirectly by measuring the pressure drop across the fluidized bed and directly by particle image velocimetry (Westerweel, Dabiri & Gharib 1997)
It was found that the charge acquired by polyethylene particles in a fluidized bed made of soda-lime glass walls depends heavily on the humidity of the fluidizing gas
Summary
When two solid surfaces are brought into contact and separated, a net charge transfer may occur between the surfaces. Most attempts to model triboelectric charging are based on the concept of effective work function difference or contact potential difference between surfaces (Harper 1967; Matsuyama & Yamamoto 1995; Tanoue et al 2001; Laurentie, Traoré & Dascalescu 2013; Korevaar et al 2014; Mizutani, Yasuda & Matsusaka 2015; Grosshans & Papalexandris 2016a,b), which can be regarded as the high-density limit of the surface state theory (Lowell & Rose-Innes 1980). A relatively simple condenser model is commonly used to determine the electric potential difference due to the transferred charge, usually by treating the contact areas as uniformly charged parallel plates (Matsusaka et al 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
