『Rainwater pipeline 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. Procurement of Doppler flow meters for sewers
2. Calculation method for rainwater volume
The amount of rainwater falling is measured by a self recording rain gauge (as shown in the figure). The runoff of rainwater can be measured by flow meters installed in channels or pipelines, or calculated from the amount of rainwater falling. There are various methods for calculation. The catchment area of rainwater pipelines is generally not large, so the determination of design flow is often based on the method of estimating small catchment surface runoff. Generally, the inference formula is used: rainwater volume Q=с Fq=167 с Fi, where Q is the design flow of rainwater pipelines (liters/second); с is the runoff coefficient (the ratio of rainwater runoff to precipitation); F is the catchment area (in hectares); Q is the design rainstorm intensity, in unit area rainfall flowmeter [L/(s · ha)]; I is the design rainstorm intensity, measured in rainfall depth (mm/min). Drainage pipelines are often designed in sections. The catchment area F of the rainwater pipeline design section can be obtained from the plan of the rainwater pipeline system. The runoff coefficient с is determined based on ground conditions and empirical data. For paved surfaces such as roofs, pavements, and sites, 0.8 or 0.9 can be used, while for green spaces, 0.1 or 0.15 can be used. Generally, it is used according to the specifications for rock dust meters. Due to the numerous and complex factors affecting the runoff coefficient, its numerical accuracy is not high. The design rainstorm intensity shall be selected according to the local rainfall records. Due to economic constraints, the maximum value that has occurred in history cannot be used
1, b, C, n are parameters related to regional meteorological conditions. It can be seen that the value of i is the average intensity during the time period t. There are many time periods and corresponding i values in a shower, and the i value in the equation is the maximum value among them. The instantaneous flow rate of the design section is collected by the rainwater at various points on the drainage surface, so the design rainfall duration should be equal to the time it takes for the farthest point on the drainage surface to flow to the calculation point. It consists of two parts: one is the surface water collection time, which can be estimated or estimated using certain empirical formulas, usually around 5 minutes; The other part is the duration of rainwater flow in the pipeline, which varies with the length of the process and can be calculated. For the same duration (e.g. 10 minutes), the corresponding i value (e.g. i10) for each shower is different, with heavy rain having a higher value and light rain having a lower value. The recurrence interval p also affects the magnitude of i value. For example, when p=2 years, the i10 value is (i10) 2, indicating that there is an average of one shower every two years, and its i10 is equal to or greater than (i10) 2; The larger the modulus p-value, the larger the (i10) p. The determination of design return period depends on the tolerance o
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