EFFECT OF REYNOLDS NUMBER IN CORIOLIS （在科里奥利雷诺数效应）.pdfVIP

EFFECT OF REYNOLDS NUMBER IN CORIOLIS FLOW MEASUREMENT Christof Huber, Michael Nuber and Martin Anklin Endress+Hauser Flowtec AG, Kägenstr. 7, 4153 Reinach, Switzerland Abstract In hydrocarbon measurement changing process conditions are the norm. Studies with highly viscous fluids have indicated there may be a shift in the calibration factor of Coriolis mass flow meter (CMF). According to those studies below a certain Reynolds (Re) number, the meter reads below the actual mass flow. In highly viscous fluids it’s possible to achieve low Re numbers with a sufficient mass flow. As direct mass flow meters CMF are independent of the flow profile. Fluid structure simulations show that the shift is caused by an oscillatory shear or viscous effect in the CMF tubes due to the interaction between oscillating Coriolis forces and oscillating sheer forces. The ratio of these two forces is reflected in the Re number of the flow. This is a strongly deterministic effect only depending on the Re number. Some CMF are able to measure the Re number. Subsequently a correction of the meter factor on-line would be possible, giving even higher accuracy under harshest conditions. This paper explains the mechanism behind this effect and presents data from different Coriolis meters ranging from 3” up to 14” showing how to ensure highest accuracy and repeatability for very low to high Re numbers. The importance of accuracy and repeatability is tremendous considering the amount and cost of hydrocarbons flowing through pipes each hour. Introduction When measuring hydrocarbon fluids strong variation of their properties – namely density, viscosity and compressibility – may occur. This band-width of physical properties can increase variations in the behaviour of the fluid flow in pipe lines. A Coriolis mass flow meter should be able to compensate such changes in fluid-flow