Pressure measurement and temperature measurement are two commonly used methods for measuring saturated vapor density, each with its own advantages. The advantage of the pressure measurement method is that it adopts a segmented linearized density model, which is relatively simple to calculate, has high calculation accuracy and fitting accuracy, and the pressure sensor responds quickly to changes in steam pressure with good real-time performance. The disadvantage of the pressure measurement method is that the temperature resistance of the pressure sensor is poor, and cooling measures or isolation methods need to be taken during measurement. Alternatively, the sensor can be installed outside the pipe and the steam pressure can be measured using the induced pressure method, which complicates the pressure measurement device and increases installation costs. From the current market prices, pressure sensors are priced higher than temperature sensors.
The pressure transmitter is installed at a distance of 3D to 5D downstream of the flow meter. The pressure at this point represents the pressure at the outlet of the flowmeter, so the density calculated using this pressure is also the density at the outlet of the flowmeter.
According to the relationship between saturated steam density and pressure, using this set of piecewise linearized calculation formulas to calculate the density of saturated steam, the accuracy can reach ± 0.1%. If the accuracy of the pressure transmitter is 0.2% soil and the basic error of the flow meter is 1% soil, then the measurement accuracy of saturated steam flow can be better than 1.5% soil.
2、 Temperature measurement method saturated steam flowmeter
The temperature transmitter is installed at a distance of 6D to 8D downstream of the flow meter. The temperature of saturated steam at this point is basically the same as the temperature inside the measuring tube of the flowmeter, so calculating the density of steam based on the temperature measured at this point represents the actual density of steam. According to the relationship between saturated vapor density and temperature, the density of saturated vapor can be calculated.