Abstract
The paper presents the results of the experimental and numerical analysis of a six-hole orifice flow meter. The experiments were performed on humid air in a 100 mm diameter duct. The aim of this research was to investigate the mass flow and pressure drop dependency in an orifice of a predetermined shape and to compare the results obtained with computational formulas recommended in the ISO 5167-2 standard for a single-hole orifice flow meter. The experiments and calculations were performed on several multi-hole orifice geometries with different contraction coefficient in a wide range of Reynolds numbers. The pressure was probed immediately upstream and downstream of the orifice. The flow coefficient determined for the six-hole orifice flow meter investigated was compared with the flow coefficient of conventional single-hole orifice with the same contraction coefficient. The results from computational formulas for single-hole orifice from ISO 5167 are also included in the paper. During some experiments, an obstacle has been introduced in the duct at variable distance upstream from the orifice. The effect of the thus generated velocity field disturbance on the measured pressure drop was then investigated. Numerical simulation of the flow with the presence of the obstacle was also performed and compared with experimental data.
Highlights
Accurate fluid mass flow measurement is required in many industrial applications
The mass flow rate was measured by the single-hole orifice
The experimental analysis showed that the empirical formula for pressure drop calculation in a single-hole orifice flow meter, included in the ISO 5167 standard [10], can be successfully used for the investigated six-hole orifice flow meters
Summary
Accurate fluid mass flow measurement is required in many industrial applications. Common flow measuring devices such as the orifice meter, venturi meter and nozzle meter use pressure drop for determining the mass flow rate. In ISO 5167-2 standard there is presented computational procedure [1,2] for mass flow determination for this kind of orifice. Such devices are characterized by simplicity of the design, reliability (no moving parts) and low manufacture cost. They have been standardized and approved for measurements relating to financial clearings. The main advantage of a multi-hole orifice is better resistance to flow disturbance [5,9], which should result in a shorter length of the required pipeline sections up- and downstream of the orifice. The recommended upstream section length, after 90◦ turn, for a single-hole orifice [10] can exceed 40 duct diameters, while using a multi-hole orifice could allow
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