CFD Modeling of Elbow and Orifice Meters

Abstract

Elbow and Orifice meters are two of the common flow measurement systems which are used to determine the pressure difference occurring as a fluid flows change by resistance. This differential pressure exists when a flowing changes direction due to a pipe turn as in the case of Elbow meter. The pressure difference results from the centrifugal force. Since pipe elbows exists in plants and its cost is very low. However, the accuracy is very poor [2]. Due to the fine pressure measurements required for the orifice meter, small changes in the physical geometry leads to large errors in the flow meter calculation. For example, if the fluid flow rate is too large for a given orifice, cavitation can occur, causing wear on the orifice. The same would be true for fast moving fluid with solid particulates included in the flow. For this reason, an additional study was conducted on an orifice plate with a slightly enlarged orifice to determine the sensitivity of flow measurements in regards to the orifice diameter.

The purpose of this paper is to run a CFD Model (Computational Fluid Dynamics) at Elbow and Orifice meters using Solidworks Flow Simulation [1] with different pipe sizes, ranging from nominal diameter. The CFD Simulation will be extended to run with using different fluid

viscosities, varying as air, steam, oil and water. The goal is to determine the sensitivity of flow measurements in regards to these parameters. The results will be compared to a corresponding theoretical solution to investigate how much the accuracy can be improved by changing the geometry of the pipes and fluid viscosities.