Compensation for high-temperature and high-pressure gas flow rates
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Could you help? In the P&I diagrams for ammonia synthesis, the \"flow display instruments\" are connected via electronic signal wires to the temperature and pressure sensors of the material being measured. According to experienced engineers, this is done for the purpose of compensating (correcting) the flow value based on temperature and pressure. In my understanding, for example, when using a orifice flow meter, since the density of gas varies under different temperatures and pressures, the pressure difference measured for a fluid with the same mass flow rate differs; therefore, there is a need for compensation (correction) of the flow rate based on temperature and pressure. Could someone explain the calculation principles and methods related to temperature and pressure compensation? Please, everyone! ! !
Flow meters require compensation, as the original poster mentioned; they measure only the pressure difference before and after, which is then converted into flow rate. The magnitude of the differential pressure depends on the flow velocity of the fluid passing through the flow meter; therefore, what the flow meter actually measures is the flow velocity. Flow rate is equal to flow velocity multiplied by the cross-sectional area. Liquids are generally not easily compressible, whereas the density of gases changes upon compression due to variations in temperature and pressure. The most common forms of temperature and pressure compensation for flowmeters actually involve, for greater accuracy, additional compensation from the compression system as well. The orifice flow meter is proportional to the square root of the temperature and pressure corrections, whereas the vortex flow meter is proportional to the first power of them.