基于IAPWS-IF97的第3区水和蒸汽密度的迭代计算

目前我国稠油油田开始使用额定工作压力接近临界状态的注汽锅炉。在开发注汽锅炉时,要涉及到接近临界状态的水和蒸汽性质的计算。临界状态在IAPWS-IF97工业标准中被划分为第3区,此区的水和蒸汽性质的计算公式都与水和蒸汽的对比密度有关,而标准中并没有具体给出密度的求解方法。基于IAPWS-IF97公式推导出密度的求根方程,再采用弦截法迭代求出。这种方法运算速度快,收敛性好,算出的密度值与性质表给出值十分接近。

Iterative Computation of Water and Steam Density Based on the Third Zone of IAPWS-IF97

At present, injected gas boilers, with their nominal working pressure approaching critical state, are adopted in the thick oil fields of our country. During the design of injected gas boiler, the character of water and steam under critical state needs calculating. The critical state was assigned to be the third zone in the Industrial standard of IAPWS- IF97. The computation formula for the character of water and steam of this zone is associated with reduced density, but the solving method of the density is not given by the standard. Based on the formula of IAPWS-1F97, the root equation of density was deduced and the result was got by the chord iterative method. The operating speed of this method is quick, the convergence property is good and the calculated value of the density is close to the value given by the property table.