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Understand flow calculation formula of orifice flowmeter
2012-3-7 9:38:14

是将标准孔板与多参数差压变送器(或差压变送器、温度变送器及压力变送器)配套组成的高量程比差压流量装置,可测量气体、蒸汽、液体及引的流量,广泛应用于石油、化工、冶金、电力、供热、供水等领域的过程控制和测量。 HAKK-LG orifice plate flowmeter is a high-range specific differential pressure flow device composed of a standard orifice plate and a multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter). Measure the flow of gas, steam, liquid and diversion. It is widely used in process control and measurement of petroleum, chemical industry, metallurgy, electric power, heating, water supply and other fields. Throttle device is also called differential pressure type flowmeter, which is composed of a primary detection part (throttle part) and a secondary device (differential pressure transmitter and flow indicator) and is widely used in the measurement of gas, steam and liquid flow. It has simple structure, convenient maintenance and stable performance.
可广泛应用于石油、化工、天然气、冶金、电力、制药等行业中,各种液体、气体、天燃气以及蒸汽的体积流量或质量流量的连续测量。 Orifice flowmeter can be widely used in petroleum, chemical, natural gas, metallurgy, power, pharmaceutical and other industries, continuous measurement of volume flow or mass flow of various liquids, gases, natural gas and steam.
In simple terms, the differential pressure value requires a square output to correspond to the flow. In actual applications, the calculation is more complicated. Generally, it is rarely calculated by yourself. The following is a practical example to give you a look. 流量补偿概述差压式流量计的测量原理是基于流体的机械能相互转换的原理。 Orifice flowmeter flow compensation overview The measurement principle of the differential pressure flowmeter is based on the principle of fluid mechanical energy conversion. The fluid flowing in a horizontal pipeline has dynamic pressure energy and static pressure energy (equal potential energy). Under certain conditions, these two forms of energy can be converted to each other, but the total energy does not change. Take the volume flow formula as an example:
Q v = CεΑ / sqr (2ΔP / (1-β ^ 4) / ρ1)
Among them: C outflow coefficient;
ε expansion coefficient
Α Cross-section area of orifice, M ^ 2
ΔP Throttle device output differential pressure, Pa;
β diameter ratio
ρ1 density of measured fluid at II, kg / m3;
Qv volume flow, m3 / h
According to the compensation requirements, compensation for temperature and pressure needs to be added. According to the calculation book, the calculation idea is based on the process parameters at 50 degrees to calculate the flow rate at any temperature and pressure. The important thing is the conversion of density. Calculated as follows:
Q = 0.004714187 * d ^ 2 * ε * @ sqr (ΔP / ρ) Nm3 / h 0C101.325kPa
That is, the volume flow at the standard atmospheric pressure of 0 degrees required to be displayed on the screen.
Based on the density formula:
ρ = P * T50 / (P50 * T) * ρ50
Where: ρ, P, T represent values at any temperature and pressure
ρ50, P50, and T50 indicate that the process datum point at a 50-degree gauge pressure of 0.04 MPa can be compiled in the program by combining these two formulas.
two. Program analysis
1. Instantaneous temperature: Must be converted to absolute Celsius temperature; that is, +273.15
Pressure: Must be converted to absolute pressure for calculation. That is, the gauge pressure + atmospheric pressure compensation calculation is based on the calculation formula, and the data is stored in the PLC register. Monitor on the intouch screen at the same time.
2. Accumulation is triggered by a scanning rising edge in 2 seconds, that is, the compensation flow value (Nm3 / h) is converted into a flow value per 2S by 1800 units, and the sum is accumulated.