API MPMS 11.3.2.1:2013 pdf free download.Manual of Petroleum Measurement Standards Chapter 11.3.2.1 Ethylene Density
This standard identifies an equation of state (EOS) suitable for use in custody transfer measurement of pure ethylene(>99 %) in the gaseous, liquid, and super critical phases. Given flowing temperature and pressure, an EOS is capableof calculating density and other thermodynamic properties used to calculate mass and volumetric flow of ethylene tocustody transfer accuracy. All accuracy and uncertainty statements in this standard are limited to the EOS results anddo not include the uncertainty added by the primary and secondary measuring equipment.
2Normative References
The following referenced documents are indispensable for the application of this document. For dated references,only the edition cited applies.For undated relerences, the latest edition of the referenced document (including anyamendments) applies.
IUPAC-88 1,Ethylene(Ethene), International Thermodynamic Tables of the Fluid State,Volume 10(1988)3Terms and Definitions For the purposes of this document, the following definitions apply.
3.1
critical region
Thermodynamic state of a fluid in which phase boundaries cease to exist.
NOTE In the case of ethylene, a vapour-lquid critical region exists. Density determination is extremely sensitive in the criticalregion, as minor changes in flowing pressure can bring about significant changes in density for a given temperature.
3.2
equation of stateEos
Thermodynamic equation describing the state of matter under a given set of physical conditions.
NOTE AnEOS provides a mathematical relationship between two or more state functions associated with the material, such asits temperature or pressure.
4Ethylene Equations of State4.1General
This standard provides a reference for an ethylene EOs:
—IUPAC-88,part of the Ethylene,Intemational Thermodynamic Tables of the Fluid State，Volume 10 (1988)
publication.
IUPAC-88 is a publication that incorporates the work carried out by Jahangiri et al. 1l on ethylene. The paper”Thermodynamic Properties of Ethylene from the Freezing Line to 450 K at Pressures to 260 MPa” was published ayear or so before IUPAC published lookup tables in 1988.
he IPUAC EOS is acceptable for use in custody transfer applications. However, the user should be aware that a critical region for ethylene exists across pressures ranging approximately from 5171.1 kPa to 5860.5 kPa (750 psig to 850 psig) and temperatures ranging approximately from 10 °C to 21.1 °C (50 °F to 70 °F). Density predictions using the IUPAC EOS are not recommended in this region. For the IUPAC-88 density prediction, the estimated uncertainty of the EOS is less than ±0.08 % for pressures up to 260 MPa (65,266.9 psig) and temperatures up to 176.85 °C (350.3 °F), with the exception of the critical region.
4.2 IUPAC-88 Equation of State The paper by Jahangiri et al. [1] is the basis for the IUPAC-88 EOS. According to the paper, the Helmholtz energy for ethylene is given below by the fundamental equation:
(1) where is the ideal gas contribution to the Helmholtz energy of any state. The term is the contribution represented by the compressibility of the real gas. After additional manipulation, the functional form used for the fundamental equation for ethylene is a nondimensional Helmholtz energy potential function below:
Given the equations above, it is possible to derive functions for calculating properties of ethylene such as density. The equations and procedures described in Section 5.4 of Jahangiri et al.’s paper illustrate how density can be calculated from the methods above.
5 Implementation Procedures
To properly implement an ethylene EOS, the user should follow the implementation procedures in the IUPAC-88 publication. Through mathematical manipulation it is possible to derive a form in terms of density, pressure and temperature. However, it is recognized that tolerances for solutions and validation procedures are not provided in the publication itself. To maintain industry consistency, a technical report will be issued separate of this standard providing guidance on how to perform the calculations.
Ultimately though, the end use for an ethylene EOS will determine the procedures of implementation. In some custody transfer applications, programming support could be required to implement the proper code for each EOS. In other custody transfer applications, the EOS could already be in a compiled form and available for use. An example of this would be the use of an ethylene EOS in flow computing applications to determine mass flow rate.API MPMS 11.3.2.1 pdf download.API MPMS 11.3.2.1:2013 pdf free download
