Modeling Temperature Effects on a Coriolis Mass Flowmeter
Fabio O. Costa, Jodie G. Pope, Keith A. Gillis
Coriolis mass flowmeters are known to be stable, have low uncertainty (± 0.1 %), and are insensitive to fluid properties. This meter type is used for many applications, including as transfer standards for proficiency testing and liquified natural gas (LNG) custody transfer. The meters flow tubes are constructed of materials that can significantly affect the meters accuracy as the pressure and temperature of the fluid inside them changes. Stainless steels are commonly used for flow tube construction due to their corrosion resistance. We developed a model to explain the temperature dependence of a Coriolis meter down to cryogenic temperatures. We tested our model over the range of 285 K to 318 K in this work. The temperature dependence predicted by the model agrees with experimental data within ± 0.1 %, well within the model uncertainty of 3.5 % (k = 2) that is dominated by the uncertainty in the values of E and G from the literature. We disabled the manufacturers temperature compensation in a single, dual tube, 5 cm diameter Coriolis meter to test for the accuracy of our model. The manufacturers supplied pressure correction was verified to assure all observed deviations were due to temperature effects on the meter. The goal of this work is to: 1) quantify the errors due to inaccurate temperature corrections and thereby enable more accurate use of the meter as a transfer standard, and 2) allow Coriolis meters to be calibrated in water and used for LNG transfer with little loss of accuracy. At temperatures below 100 K, the Youngs modulus and shear modulus of stainless steels display nonlinear behavior. Therefore, our model includes corrections for these phenomena. Here, basic concepts of Coriolis flowmeters will be presented, and correction coefficients will be proposed that are valid down to 5 K based on literature values of material properties.