ISO 20765-1:2005"Natural gas—Calculation of thermodynamic properties—Part 1:Gas phase properties for transmission and distribution applications"(GB/T 30491.1-2014《天然气 热力学性质计算第1部分:输配气中的气相性质》)是以AGA8方程为基础计算管输天然气热力学性质,根据亥姆霍兹自由能及其关于温度和密度的导出函数来求解,推导严格.但是,标准中的计算公式仍然有些复杂,不容易理解,并且没有明确给出理想气体焓、熵的计算公式;经过研究,利用ISO 20765-1(GB/T 30491.1)中的数据,提出了6个计算理想气体焓、熵的新公式.新公式经过严格的数学推导,是带有双曲函数和指数函数的多项式,使用简单,精确度高,其相对误差平均值小于3×10-5.
New calculation formulas of ideal gas enthalpy and entropy
ISO 20765-1 is a method for calculating the thermodynamic properties of natural gas in pipelines based on the AGA8 equation.All thermodynamic properties are obtained according to the Helmholtz free energy and its derived functions for temperature and density and the derivation is rigorous.However,the calculation of the formula in the standard is still somewhat complicated and not easy to understand,and there is no clear formula for calculating the ideal gas enthalpy and entropy.After research,the paper derives the enthalpy and entropy formulas with the data in ISO 20765-1 and proposes separately the enthalpy and entropy six formulas of ideal gases.The proposed new formulas for calculating the enthalpy and entropy of ideal gas have been rigorously mathematically derived.They are polynomials with hyperbolic function and exponential function,which are simple to use and highly accurate.Their relative error average is less than three hundred thousandths.
sideal gasesthermodynamic propertiespredictionenthalpyentropynew formula
万方数据
维普
