(419i) Interplay of Tribocharging and Transport on Particle-Laden Flows

¹Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA

²School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK

It is well known that materials can develop static charges upon mechanical contact with other materials [1]. Granular materials in transport lines and fluidized beds tend to become charged due to contacts with walls and other particles [2]. The charge distribution inside these devices remains poorly understood and has gained limited attention in the literature [3,4]. The charge distribution is affected by the interplay of timescales associated with tribocharging, charge diffusion and convection. In this study, we seek a qualitative understanding of this interplay in flow of a mixture of identical particles suspended by a gas.

To address this question, we first derive a Eulerian model for charge transport [5], which can be coupled to a kinetic-theory-based model for gas-particle flow, and supplement it with a boundary condition to capture charge transfer at bounding walls. We then examine fully developed steady state solutions afforded by this model for gas-particle flow in a channel to probe the role of the relative timescales associated with tribocharging and charge diffusion.

We then couple the charge transport model with a solver for two-fluid model and simulate flow in a model gas-particle flow problem. Comparison of the results for fully-developed flow in a channel from these unsteady simulations with those obtained with the steady-state model calculations above exposes the effect of meso-scale velocity fluctuations on the interplay between tribocharging and flow.

[1] Lacks, D., Mohan, S.. Contact electrification of insulating materials. Journal of Physics D: Applied Physics 2011; 44(45).

[2] Sowinski, A., Miller, L., Mehrani, P.. Investigation of electrostatic charge distribution in gas-solid fluidized beds. Chemical Engineering Science 2010;65(9):2771–2781.

[3] Lee, V., Waitukaitis, S., Miskin, M., Jaeger, H.. Direct observation of particle interactions and clustering in charged granular streams. Nature Physics 2015;11:733–737.

[4] Jalalinejad, F., Bi, X., Grace, JR, .. Comparison of theory with experiment for single bubbles in charged fluidized particles. Powder Technology 2016;290:27 – 32.

[5] Kolehmainen, J., Ozel, A., Sundaresan, S.. Eulerian Modeling of Gas-Solid Flows with Triboelectric Charging. Journal of Fluid Mechanics 2018: Under Review.