ABSTRACT
I. INTRODUCTION When a dielectric liquid flows through a pipe from one vessel to another, the potential difference that appears in the collecting vessel is due to the accumulation of charges. These charges result from the convection of a part of the electrical double layer existing in the tube at the contact be tween the liquid and the inner wall (Boumans, 1957; Klinkenberg, 1967; Gavis, 1964; Gibbings, 1970). Indeed, at the liquid/solid interface, the electrochemical reaction induces an electrical double layer composed of two layers in the liquid: the compact layer very close to the wall (unaf fected by the flow), and a diffuse layer that can be convected (Touchard et al., 1985). Then the space charge density Q convected in a pipe by a flow is given by the ratio of the charge convected to the flow rate Q = /spuds/JsQds, where s is the section of the pipe, p the space charge density, and ΰ the mean axial velocity. To compute this quantity, we need to know the velocity profile and the space charge density profile, which is a function of three parameters: the electrochemical reaction at the inter face, the diffuse layer thickness, and the characteristic of the flow. To analyze the phenomenon, first it is important to know the space charge density profile for a diffuse layer at rest in the pipe (without flow), and then we must understand how it is affected by the flow (Touchard, 1978).
