Performance assessment of ISO-5167 and symmetrical Venturi meters for measuring low Reynolds number turbulent incompressible isothermal flow

Abstract

The selection of Venturis depends on the desired flow measurement sensitivity, permanent pressure loss, discharge coefficient, and relative pressure loss coefficient. The ISO-5167 standard specifies geometries for Venturi metres within the Reynolds number range of 200,000 to 2,000,000. This study evaluates the performance of ISO-5167 and six suggested symmetrical Venturis operating in both unidirectional and bidirectional flow conditions for flows with Reynolds numbers below 200,000. The performance of ISO-5167 and six suggested symmetrical Venturis with β-ratios of 0.4 and 0.55, and cone angles of 10°, 20°, and 40° degrees were evaluated. The study found that the ISO-5167 Venturi performed best in the conventional flow direction for flows with Reynolds numbers greater than ≈34,000. The symmetrical Venturi meter with a β-ratio of 0.55 and a cone angle of 10° (SVD4) exhibited performance comparable to the ISO-5167 Venturi for the conventional flow direction. The ISO-5167 Venturi exhibited a significant flow reversal when operating in the opposite direction to the conventional flow. The SVD4 Venturi metre demonstrated the potential to save 71 % of energy in the reverse flow direction compared to the ISO-5167 Venturi, suggesting an energy saving of up to 43 % in certain bi-directional flow scenarios.

Keywords

• Venturi flow meter
• Beta-ratio (β)
• Convergent cone angle
• Divergent cone angle
• Pressure loss
• Relative pressure loss coefficient (ζ)