What should you pay attention to when measuring steam with a vortex flowmeter?

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What should we pay attention to when measuring steam with a vortex flowmeter? What is the best method for installing a vortex flowmeter to measure steam? Can vortex flowmeter be used for steam metering? The measurement performance of vortex flowmeters is evaluated under single-phase flow conditions. There is currently no evaluation standard for system changes when flowmeters calibrated with single-phase flow are used to measure two-phase flow. However, two-phase flow exists objectively, and its impact on flow measurement is unavoidable. Although there are many difficulties, people are still trying to study the mechanism of its impact on flow measurement, and take corresponding countermeasures to improve flow measurement. Steam flow difficulties: During long-distance transportation, dry steam will partially condense due to heat loss, causing the dryness of the steam to decrease and turn into wet steam. The gas-liquid two-phase flow structure in horizontal pipes is related to the gas-liquid two-phase volume ratio and flow speed. In steam pipes, since the volume ratio of condensed water in wet steam is very small after all, the drain pipe led from the bottom of the horizontal pipe can achieve a good hydrophobic effect. When the flow rate is particularly high, it will also appear as annular flow, that is, there is a liquid film on the pipe wall, and the central part of the pipe is a gas core with liquid droplets. Due to the influence of gravity during horizontal flow, the lower liquid film is thicker than the upper pipe wall. In vertical ascending pipes, the basic structures of gas-liquid two-phase flow include fine bubble flow structure, elastic flow structure, block flow structure, annular flow structure with fibers and annular flow structure. However, since the volume of condensed water in wet steam is relatively small, the flow of excess water in the ascending pipe often appears as an annular flow structure. However, when the amount of water carried is particularly large, it may also appear as an annular flow structure with fibers. Among them, the fibrous fluid is actually condensation water connected into strips. Flow in a vertical descending pipe: In a vertical descending pipe, the structure of the gas-liquid two-phase flow is very similar to that of vertical ascending flow, but there is a difference. Not only is the flow direction opposite, but also when the average flow velocity is the same, the flow rate of the liquid in the vertical descending pipe is much faster than the flow rate of the liquid in the vertical ascending pipe. If you want to accurately measure steam with a vortex flowmeter, you should arrange the steam trap reasonably.: People have long discovered that when the steam contains a lot of water, the vortex flowmeter will have a "pulse leakage" phenomenon. That is, when the steam flow rate is stable, the vortex flowmeter should have a stable pulse output proportional to the flow rate. But sometimes it is found that the output pulses of the instrument are inexplicably less. From the distribution of the recorded output pulses on the two-dimensional coordinates, it can be clearly seen that the pulses that should be approximately uniformly distributed are missing one pulse at a certain place. In serious cases, there are many pulses missing, and in serious cases there are no pulses at all. This may be related to the fact that unevenly distributed larger droplets impact on the vortex generator, inhibiting the formation of vortex arrays. If you want to accurately measure steam with a vortex flowmeter, you should arrange the steam trap reasonably.: The reasonable arrangement of hydrophobic points plays a key role in sufficient hydrophobicity. Wet steam is a two-phase fluid in terms of properties, but when the humidity is not high, it can be treated as a single-phase fluid and measured with a general flow meter. If the steam is seriously laden with water, the vortex flowmeter will have a "pulse leakage" phenomenon. In more severe cases, the vortex flowmeter will have no pulse output at all. For situations where the steam is severely water-laden and affects the normal measurement of the vortex flowmeter, a common treatment method is to fully hydrophobicize the water at an appropriate position upstream of the vortex flowmeter. Reasonably arrange the steam trap to maximize the dryness of the wet steam and ensure normal measurement by the vortex flowmeter.