On the issue of calculating the flow rate under operating conditions for orifice plate flow meters using a U-tube manometer
Thread Content
This post was last edited by SpeedyDriver on 2020-5-3 at 18:19. Flow rate under mixed conditions refers to the flow rate of fluid through a pipe under the existing temperature and gauge pressure. Standard condition flow rate refers to the flow rate at 0° (273 K; for natural gas, it is 20°, or 293 K) and 101.325 atmospheres of pressure. A standard-condition scalar quantity is defined as a standard-condition vector quantity multiplied by the gas concentration. To convert operating conditions to standard conditions, the ideal gas law should be applied: P1*V1/T1 = P2*V2/T2. This formula is used to transform operating conditions into standard conditions. According to the instructions in MT/T 642, the mixed flow rate should be calculated using the formula: Mixed flow rate = Orifice plate coefficient * Square root of pressure difference * Temperature correction * Pressure correction * Gas concentration correction; however, the value obtained by applying these corrections should represent the mixed flow rate under standard conditions. Moreover, this standard further states that the pure gas flow rate = mixed flow rate × gas concentration, which also confirms that the formula for calculating the mixed flow rate is one based on standard conditions. But this raises a question: how can the flow rate under operating conditions be calculated using an orifice plate and a U-tube manometer? Which formula should be used to calculate the flow rate under operating conditions based on the pressure difference across the orifice plate? There’s a problem with this that I just can’t figure out.
Go up there and ask the expert to take a look. . .
Go up there and ask the expert to take a look. . .
For each orifice plate, the operating conditions and the flow rate range for measurement are determined at the time of design; it simply corresponds to the differential pressure value – is any further calculation necessary? I didn’t understand the original poster’s question
This post was last edited by SpeedyDriver on 2020-5-14 22:59. I know this; if the operating conditions vary, I know which formula to use after determining the pressure difference For example, for a hole plate with a diameter of φ200mm and a water column pressure difference of 1200 Pa, what should be the corresponding flow rate under those conditions?
I’ve heard of operating conditions and standard conditions – why is there also some extra term included? I don’t understand. To determine whether differential pressure flow meters can accurately measure your natural gas, it is necessary to consult specialized research data or practical applications in this field; do not rely on basic formulas arbitrarily.
It needs to be stated in the calculation sheet provided by the orifice plate supplier; according to the data in my diagram, the flow rate and the square root of the pressure difference are directly linearly related
This post was last edited by zxg.wylton on 2020-5-15 at 11:06. Additional note: Middle school physics teaches that global communication is possible with just 3 satellites, but what about in practical engineering applications? Also, give me a fulcrum – can I leverage the Earth?:P
The last edit to this post was made by cqdfwy on 2020-6-11 at 16:05. It’s not enough to know the orifice diameter and the differential pressure to calculate flow rate; the flow coefficient C also needs to be determined. In other words, to calculate the flow rate of a gas using an orifice plate, it is also necessary to know the density of the gas (the components of the mixed gas and the molecular weights of those components). In short, flow rate calculation is quite complex, as it involves the computation of various intermediate parameters such as the gas compressibility factor, expansion coefficient, and heat of combustion, among others. The calculation for gases, which are mixed gases similar to natural gas, can be understood by referring to the example titled \"Calculation Example for Measuring Natural Gas Flow Rate Using a Standard Orifice Flow Meter\" posted on floor 9.