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『Flow coefficient of Venturi flowmeter』Related information(clamp on meter|electromagnetic meter|venturi meterrotameter|orifice meter|ultrasonic flow meter|mass flow meter|coriolis mass flow meter|coriolis flow meter|magnetic flow meter|magmeter flow meter|magflow flow meter|mag meter flow meter|electromagnetic flow meter|vortex flow meter|turbine flow meter|thermal mass flow meter|thermal flow meter|rotameter flow meter)
1. What are the types of mass flow meters?
2. Can the flow coefficient of a Venturi flow meter be greater than 1?
It cannot be greater than 1, because the flow coefficient of a Venturi flow meter is equal to the ratio of the actual flow rate of the liquid to the theoretical flow rate of the Venturi flow meter. However, the actual liquid experiences head loss during movement, so the actual flow velocity is smaller than that of the Venturi flow meter. Since Q=AV, Q The Venturi tube flow rate calculation adopts the standard formula derived from Bernoulli equation and continuity equation, and the core parameters are upstream and downstream pressure difference, throat cross-sectional area, and fluid density. 1. The core calculation formula for the volumetric flow rate (Q) of a Venturi tube is: Q=C_d × A ₂ × √ {[2 × (P ₁ - P ₂)]/[ρ× (1- (A ₂/A ₁) ²)]}, where: • C_d: Discharge Coefficient, which needs to be obtained through real flow calibration. Ideally, it is about 0.98, and the actual value depends on the specific geometry and Reynolds number of the pipeline. • A ₁: Upstream pipeline cross-sectional area (m ²) • A ₂: Throat cross-sectional area (m ²) • P ₁: Static pressure measured at the upstream pressure tap (Pa) • P ₂: Static pressure measured at the throat pressure tap (Pa) • ρ: Fluid density (kg/m ³) 2. Key calculation steps 2.1 Measuring pressure difference: Accurately measure the static pressure difference between the upstream and throat using a high-precision differential pressure transm3. Venturi tube flow rate
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2.2 Determine geometric parameters to accurately measure the inner diameter of the upstream pipeline (D ₁) and the inner diameter of the throat (D ₂), and Calculate the corresponding cross-sectional area: A ₁=π× (D ₁/2) ² A ₂=π× (D ₂/2) ² 2.3 Obtain fluid properties by looking up a table or obtaining the density (ρ) of the fluid under current operating conditions through sensors. For compressible fluids (such as gases), it is necessary to introduce the coefficient of expansion (ε) for correction, and the formula will be more cumbersome.
2.4 The selection of flow coefficient and flow coefficient, C_d, is the key to accurate calculation. The coefficient must be selected based on manufacturing codes such as calibration curves provided by manufacturers or relevant standards (such as ISO 5167), which is the only starting function of Reynolds number and β value (β=D ₂/D ₁)
2.5. Perform calculations by substituting all the above parameters into the core formula for calculation. For ease of use, formula constants and geometric parameters are usually combined into one flow coefficient K, simplified as: Q=K × √ (Δ P/ρ)
3. Operation precautions Installation requirements: It is necessary to ensure that the length of the front straight pipe section is sufficient (usually 10-20 times the pipe diameter) to ensure the full development of the fluid, symmetrical and stable flow velocity distribution, which is the prerequisite for obtaining accurate pressure difference. Anti clogging maintenance: Used for measuring fluids containing impurities or prone to scaling, the pressure tapping hole is prone to clogging and requires a flushing or blowing interface desi