So, with every collision, the kinetic energy is converted into pressure energy. This brings them to a full stop and they lose their kinetic energy.īut energy is never lost. Because the fluid can no longer enter the pitot inner tube, all molecules will collide at the front hole. However, the fluid continues to flow through the conduit and the molecules build up kinetic energy. So, once the tube has filled up, the fluid will come to a standstill (stagnation) inside the tube. This pressure is called static pressure.Īs soon as the fluid starts to flow, a part of the fluid will enter the pitot tube through its front hole, but it has nowhere to go because the inner tube is closed at the back as it is connected to the pressure transmitter. If the fluid is not flowing, the pressure will be the same in the inner and outer tubes. The drawing above is showing a classical pitot tube inserted into a conduit with the tube opening oriented against the flow. Both chambers come out separately at the top of the pitot tube for connection to the pressure instrument. More recent designs are made of a straight multi-chamber tube, perpendicular to the flow direction, with multiple holes in the front and the rear chamber of the tube. The inner and outer tube walls are connected to each other at the front hole, while at the other end both tubes are available for connection to a differential pressure instrument. What is a pitot tube?Ī pitot tube, named after the French engineer Henri Pitot, is the sensing element of a differential pressure measurement that is used to measure the flow velocity of liquids and gases, including steam.Ĭlassical designs have an L-shaped double-walled tube with the open end facing upstream and eventually one or more holes in the outer tube wall behind the open end. We will discuss the different pitot tube types and look for the underlying principles that ensure that the pitot tube does what it should do, that is to measure the flow velocity.īut let’s start from the beginning. In this post, we will take a closer look at the pitot tube flow meter. Home » Flow measurements » pitot-tube-flow-meter Pitot tube flow meter The working principle of pitot tubes for measurement of volumetric flow
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