The average flow velocity in the piping can be easily measured with a porous pitot tube.
The Pitot tube has a rod-like shape. It is inserted vertically into the piping to measure flow rate. Holes are provided on the rod to detect total pressure and static pressure. By measuring the differential pressure (also called dynamic pressure), the flow velocity of the fluid flowing in the pipe can be determined. The multi-hole Pitot tube has multiple holes on the rod that comply with JIS B 8330, allowing for the measurement of average flow velocity. The two pressure sensing pipes that exit the Pitot tube are connected to the high-pressure and low-pressure sides of a differential pressure transmitter. The differential pressure is converted to flow rate through square root calculation processing by the differential pressure transmitter. It is often used for measuring exhaust gas flow rates in large-diameter ducts. Large-diameter ducts (300A or 500A and above) cannot be manufactured with orifice plates or are very costly, making the Pitot tube flow meter a strong option. Among flow meters, the Pitot tube is simple and relatively low-cost.
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basic information
The Pitot tube is characterized by very low pressure loss compared to differential pressure flow meters with orifice and other throttling shapes. In the case of gases, the resulting differential pressure is on the order of several tens of Pa. However, it is important to note that a differential pressure transmitter must also be selected for micro differential pressure. The relationship between flow velocity and differential pressure is derived from Bernoulli's equation. The flow velocity V when a differential pressure ΔP occurs in the Pitot tube is expressed by the following equation: V = K / √(2ΔP/ρa) where ρa is the density of the fluid (kg/m²), and K is a correction factor specific to the Pitot tube, known as the Pitot tube coefficient. Additionally, the equation to determine ΔP from the flow velocity V is as follows: ΔP = ρa/2 (VK)² Like other differential pressure flow meters such as orifices, the differential pressure is proportional to the square of the flow velocity.
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Large-diameter duct and exhaust gas flow measurement
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JMES Co., Ltd. was established in July 1976 with the keyword "environmental measurement." Since then, as a pioneer in environmental measurement in Japan, we have contributed to domestic environmental measures by starting with the import of excellent measuring instruments from overseas and engaging in domestic manufacturing. We have also expanded our business into energy conservation and plant corrosion prevention equipment as an extension of environmental measurement. In September 2003, we obtained ISO 9001:2000 certification (updated to ISO 9001:2015 in September 2021) (LRQA Limited). We promise to further enhance customer satisfaction with our products and services. We position compliance with laws and regulations as our top priority and are committed to advancing as a company to realize our motto, "Make Japan Beautiful."
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