Performance of models to determine flow rate using orifice plates

ABSTRACT This study aimed to evaluate three methodologies for orifice-plate water-flow estimation by quantifying errors in the flow determinations to propose an appropriate measurement range for each evaluated condition. Two orifice-plate models (nominal diameters of 100 and 150 mm) with 50% restriction in the flow section were evaluated. In the theoretical equations, the discharge coefficient was obtained using the Reader-Harris/Gallagher equation (Method 1) and approximated from experimental data using the angular coefficient of a zero-intercept straight line (Method 2). The recommended measurement ranges for errors that were lower than 5% for the 100 and 150 mm plates were 30 to 65 m3 h-1 and 70 to 130 m3 h-1 using the theoretical equation and 20 to 65 m3 h-1 and 40 to 130 m3 h-1 using the empirical equation, respectively. The Reader-Harris/Gallagher equation (Method 1) adequately estimated the discharge coefficient of the orifice plates; however, the use of empirical equations (Method 3) demonstrated smaller measurement errors and greater rangeability of the evaluated flow meters.

摘要 本研究旨在评估三种孔板（orifice plate）水流流量估算方法，通过量化流量测定过程中的误差，为各评估工况提出适宜的测量范围。本次评估采用两款流通截面缩径率为50%的孔板模型，公称直径分别为100 mm与150 mm。在理论计算框架下，流量系数通过Reader-Harris/Gallagher公式（方法1）获取，同时可通过零截距直线的斜率由实验数据拟合得到（方法2）。当误差低于5%时，采用理论公式时，100 mm与150 mm孔板的适宜测量范围分别为30~65 m³·h⁻¹与70~130 m³·h⁻¹；采用经验公式时，对应范围分别为20~65 m³·h⁻¹与40~130 m³·h⁻¹。Reader-Harris/Gallagher公式（方法1）可较好地估算孔板的流量系数；而采用经验公式（方法3）则展现出更小的测量误差与更宽的量程范围。