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| speedpump |
 Posted: Wed Mar 03, 2010 8:52 pm Post subject: About Pitot tube, need help please |
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Joined: 03 Mar 2010
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I need additional information on pitot tube, I did a lot of research and I know how it works in general. But I need information in some details, escecially in straight type tubes. How do those side holes measure static pressure? What type of pressure transducer are being used? Can I possibly reduce the middle part of the tube as it's a bit thick? I dont need heating since I wont use it for avionic purpose. Greatly appreciated if anyone can answer any of my questions. Thanks.
http://www.spaceagecontrol.com/pm/uploads/Main.PitotAndPitot-StaticProbes/4207REFONLY.pdf
I forgot to add the link, sorry |
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| cypress |
| Posted: Thu Mar 04, 2010 8:24 pm Post subject: |
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Banned (Trolling)
Joined: 11 Sep 2009
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Location: New Orleans
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pitot tubes have and inner tube with no side holes to measure kinetic pressure at the tip and an outer tube with holes on the side to measure base or static pressure. They measure static pressure because the holes perpendicular to flow do not impede or block flow and therefore do not alter the localized pressure at that point. The tip tube blocks flow and causes the fluid or gas velocity to drop to zero right at the entrance to the tube. The kinetic energy is thus converted to potential energy in the form of higher pressure in the tube. The difference between the two pressures is therefore a function of the velocity of the fluid flowing past the tube.
You can make the middle part of the tube in tube assembly as thin as you like as long as it is structurally sound and requires no insulation to prevent condensation or icing. You can use a simple water/liquid column to measure differential pressure or a differential pressure transducer. In non-condensing air any transducer with sufficient range to measure maximum velocity is fine. Honeywell makes a variety of inexpensive transducers ($35-$150) including board mounted ones. In liquid applications, you have to be careful not to allow entrained gas to get into the tubes. Best is to keep the tubes nearly horizontal with a slight downward tilt and the tubes straight with constant slope.
Good luck.
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| speedpump |
| Posted: Fri Mar 05, 2010 8:45 am Post subject: |
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| THANK YOU!! i been looking for those answers for a while. The tube will be placed in horizontal position without problem. It's in a sealed environment, air and condensation is not a problem too. I will use column transducer leveled up with the tube from outside to measure the pressure. I juust have 1 addtional question, is it possible to make the inner tube about 0.2 mm and outer tube about 0.5 mm including the stainless steel body? thank you so much |
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| cypress |
| Posted: Fri Mar 05, 2010 11:02 pm Post subject: |
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I would think so. The inner tube of course has to be knurled outward at the tip and then the two must be sealed together so the outer tube does not get any airflow into it from the front.
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