Developing novel correlations for calculating natural gas thermodynamic properties

Abstract

Natural gas is a mixture of 21 components and it is widely used in industries and homes. Knowledge of its thermodynamic properties is essential for designing appropriate processes and equipment. This paper presents simple but precise correlations of how to compute important thermodynamic properties of natural gas. As measuring natural gas composition is costly and may not be effective for real time process, the correlations are developed based on measurable real time properties. The real time properties are temperature, pressure and specific gravity of the natural gas. Calculations with these correlations are compared with measured values. The validations show that the average absolute percent deviation (AAPD) for compressibility factor calculations is 0.674%, for density is 2.55%, for Joule-Thomson coefficient is 4.16%. Furthermore, in this work, new correlations are presented for computing thermal properties of natural gas such as enthalpy, internal energy and entropy. Due to the lack of experimental data for these properties, the validation is done for pure methane. The validation shows that AAPD is 1.31%, 1.56% and 0.4% for enthalpy, internal energy and entropy respectively. The comparisons show that the correlations could predict natural gas properties with an error that is acceptable for most engineering applications.

Effects of Natural Gas Compositions on CNG Fast Filling Process for Buffer Storage System

“…The method for calculating these properties are discussed in this section. The detailed methods for calculating most of natural gas thermodynamic properties are presented in Farzaneh-Gord and Rahbari [29][30]. The thermodynamics relationship presented here, could be also found in most of thermodynamic text books including Moran and Shapiro [31].…”

A novel method for calculating natural gas density based on Joule Thomson coefficient

“…Most broadly employed standard EOSs are AGA8 and GERG2008 [13][14][15]. EOSs also need the natural gas mixture temperature, pressure and compositions to calculate its density.…”

“…There are also other authentic references in this field [19][20][21][22][23]. In one of the last studies, Farzaneh-Gord and Rahbari [14] developed novel correlations for calculating most thermodynamic and thermal properties of natural gas such as density based on AGA8 EOS. In the study, each thermodynamic property is a functional of natural gas pressure, temperature and specific gravity.…”

“…In the study, each thermodynamic property is a functional of natural gas pressure, temperature and specific gravity. These methods were developed by Farzaneh-Gord and Rahbari [14] and were previously presented in Farzaneh-Gord et al [24,25] and Marić [26][27][28].…”

“…The JT coefficient is calculated by measuring pressure and temperature drop during pressure reduction process. Finally natural gas mixture density is calculated using the thermodynamic equations [14]. Note that, the presented method could be combined with any volume flow meters to calculate natural gas mass flow rate.…”