Evaluating measurement uncertainty in fluid phase equilibrium calculations

• Published in: Metrologia Vol. 55; no. 2; pp. S60 - S69
• Main Author: van der Veen, Adriaan M H
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.04.2018
• Subjects: Computational fluid dynamics; equation-of-state; flash calculation; Fluids; Iterative methods; Liquid-vapor equilibrium; Measurement; measurement uncertainty; Monte Carlo method; Phase equilibria; Physical chemistry; Propagation; Thermodynamics; Uncertainty; Vapor pressure; vapour pressure equation; vapour-liquid equilibrium
• ISSN: 0026-1394; 1681-7575
• DOI: 10.1088/1681-7575/aaa6dd

The evaluation of measurement uncertainty in accordance with the 'Guide to the expression of uncertainty in measurement' (GUM) has not yet become widespread in physical chemistry. With only the law of the propagation of uncertainty from the GUM, many of these uncertainty evaluations would be cumbersome, as models are often non-linear and require iterative calculations. The methods from GUM supplements 1 and 2 enable the propagation of uncertainties under most circumstances. Experimental data in physical chemistry are used, for example, to derive reference property data and support trade-all applications where measurement uncertainty plays an important role. This paper aims to outline how the methods for evaluating and propagating uncertainty can be applied to some specific cases with a wide impact: deriving reference data from vapour pressure data, a flash calculation, and the use of an equation-of-state to predict the properties of both phases in a vapour-liquid equilibrium. The three uncertainty evaluations demonstrate that the methods of GUM and its supplements are a versatile toolbox that enable us to evaluate the measurement uncertainty of physical chemical measurements, including the derivation of reference data, such as the equilibrium thermodynamical properties of fluids.