Electrostatic charges convected by flow of dielectric liquid through pipes of different length and different radii, (Theoretical model and experimental results)

Abstract When a dielectric liquid flows through a pipe, electric charges are generated, the magnitude of which depends upon the material properties of the pipe, the properties of the liquid and the parameters of the flow (1) (2) (3) (4) (5). A theory is presented for electric charging process. It is shown that the process can be characterized by the convection of a part of the double layer appearing at the pipe-liquid interface. The liquid is supposed electrically neutral at the entrance of the pipe, then an electrical diffuse layer is developed in terms of different parameters and specially the radius of the pipe, the Reynold's number of the flow, the conductivity of the liquid and the charge transfer at the wall. Such a model is analysed and theoretical results are obtained for the streaming current in the first part of the study. Then in a second part experimental data are presented on the charge convected in heptane liquid through pipes of radii ranging from 1.25mm to 0.24mm and of length ranging from 4.m to 0.08m. The comparison between experimental data and theoretical model shows good agreement, more so it points out that the process is mainly controlled by the wall current density and not the diffusion.