Pitot Tube
It is also known as insertion tube
The size of the sensing element is small compared to the flow channel
One tube is perpendicular to the flow direction and the other is parallel to the flow
Two tubes are connected to the manometer
∆Hp = u2/2g
U2= velocity of the flow at the point of insertion
∆ HP= difference in head from monometer, m
A pitot tube is a pressure measurement instrument used to measure fluid flow velocity
The pitot tube was invented by the French engineer Henri Pitot in the early 18th century and was modified to its modern form in the mid19th century by French scientist Henry Darcy
It is widely used to determine the airspeed of an aircraft, water speed of a boat, and to measure liquid, air and gas velocities in industrial Applications
The pitot tube is used to measure the local velocity at a given point in the flow stream and not the average velocity in the pipe or conduit
Working
• Tube are inserted in the flow shown is the figure
U2 = Cv √2g. ∆H
• Cv = Coefficient of Pitot tube
Working of Pitot Tube
• A pitot tube is simply a small cylinder that faces a fluid so that the fluid can enter it
• Because the cylinder is open on one side and enclosed on the other, fluid entering it cannot flow any further and comes to a rest inside of the device
• A diaphragm inside of the pitot tube separates the incoming pressure (static pressure) from the stagnation pressure (total pressure) of a system
• The difference between these two measurements determines the fluid’s rate of flow
Advantages:
• Pitot tubes measure pressure levels in a fluid
• They do not contain any moving parts and routine use does not easily damage them
• Also, pitot tubes are small and can be used in tight spaces that other devices cannot fit into
Disadvantages:
• Foreign material in a fluid can easily clog pitot tubes and disrupt normal readings as a result
•This is a major problem that has already caused several aircraft to crash and many more to make emergency landings