Orifice flowmeter can be widely used in petroleum, chemical, natural gas, metallurgy, electric power, pharmaceutical and other industries to continuously measure the volume flow or mass flow of various liquids, gases, natural gas and steam. But many people do not know how to calculate orifice flow meters. Today I will discuss with you the calculation formula of orifice flowmeterIn short, the differential pressure value must be a square output to correspond to the flow rateIn practical applications, the calculation is more complicated. Under normal circumstances, it is rarely calculated by yourself. This is calculated by software. Give an example1. Overview of flow compensationThe measuring principle of the differential pressure flowmeter is based on the mutual conversion principle of fluid mechanical energy. The fluid flowing in the horizontal tube has dynamic pressure energy and static pressure energy (the potential energy is equal). Under certain conditions, the two forms of energy can be converted to each other, but the sum of energy is constant. Take the volume flow formula as an exampleQ v=C&;ε;&;Alpha;/sqr(2&; Delta; P/(1-&;β;＾4) /&;ρ;1)Among them: C outflow coefficient&; ε; Expansion coefficient; Alpha; the cross-sectional area of the orifice of the throttle member, m 2And; Delta; P differential pressure output by throttling device, PA&; Beta; Diameter ratio; ρ; Density of the measured fluid at 1 I-I, kg/m3QV volume flow, m3/hAccording to the compensation requirements, temperature and pressure compensation should be added. According to the calculation book, the calculation idea is based on the process parameters at 50°C to calculate the flow rate at any temperature and pressure. In fact, the most important thing is the conversion of density. Calculated as follows:Q=0.004714187*d＾2*&;ε;*@sqr(&A); delta; P/ and; ρ;) Nm3/h 0C101.325kPaThat is, the standard atmospheric pressure that needs to be displayed on the screen at 0℃According to the density formula:&;Ρ;=P*T50/(P50*T)*&;ρ;50Among them: &; ρ第. T is the value at any temperature and pressure&; ρ; 50, P50, T50 are 50 degrees gauge pressure 0.04MPaThe process reference point below, combined with these two formulas, can complete the program2. Program analysis1. Instantaneous amountTemperature: must be converted to absolute Celsius; that is +273.15Pressure: Must be converted to absolute pressure for calculation. I.e. gauge pressure + atmospheric pressureCompensation calculation, according to the calculation formula, the data is stored in the PLC register. At the same time, on the touch screen2 to monitor. Cumulative amountUse the scanning rising edge trigger within 2 seconds for accumulation, that is, convert the compensated flow value (Nm3/h) into a flow value every 2 seconds, and perform the accumulation. The screen has reset and clear functions.
Post time: 21-09-21