Numerical investigation on the installation effects of electromagnetic flowmeter downstream of a 90 degrees elbow-laminar flow case

Abstract

An electromagnetic flowmeter installed downstream of a 90 degrees elbow to measure the flowrate of laminar flow is numerically simulated to investigate installation effects by varying the location of the electromagnetic flowmeter at a distance up to 22D from the elbow, and the angle between the electrodes plane and the symmetry plane of the elbow at phi = 0, 45 and 90 degrees. Effects of the curvature radius (R,) and the Reynolds number (Re) based on a diameter D are also scrutinized in the range of 400 less than or equal to Re less than or equal to 1500 and R-c = 1.5D and 3.0D. For the simulation of an electromagnetic flowmeter, a commercial code FLUENT(ver. 4.4) is applied for flow field analyses and a three-dimensional numerical code is developed for analyzing the magnetic field. The developed code adopts a finite volume method to solve a Poisson-type voltage equation for the magnetic field. It is found that the deviations of the flow signal due to the disturbance from the elbow is strongly dependent on the pattern of axial velocity contours. Cases for phi = 45 degrees are found to permit significantly better measurement accuracy in comparison with phi = 0 degrees and phi = 90 degrees, and the effect of the curvature on the optimum installation distance depends on the Reynolds number. The present numerical simulation method is found to be a useful tool for the performance analysis of the electromagnetic flowmeter. (C) 1999 Elsevier Science Ltd. All rights reserved.