The forced heat convection does NOT affect the pressure quantification as long as the sensor is compensated for the whole temperature range. If you look in ANY catalog for pressure transducers you will find what you need. You may select according to 6 criteria:
- expected pressure range
- expected temperature extreme value
- accepted uncertainty level
- compatibility to your fluid
- dynamic changes of pressure AND last but not least
- your laboratory financial possibilities.
I am sure you will find at least 50 sources !
Good luck
Dear Saad Najeeb
The best way to experimentally measure the pressure drop within the small heated channels is to use a pair of single pressure transducers, the first one located at the channel inlet and the second at the channel outlet.
Dear mr. Najeeb!
It is not clear what the problem is measuring pressure.
Is the channel is too small? Is the temperature too high? Is the process too fast? Are pressure gradients too high? Is the pressure too high?
Please clarify the question.
400 C is not very high temperature. You can use stainless steel impulse tubes to trasmitt pressure from channel to any pressure sensor.
If your channel is very short - you can use very think tube. In same situations i used syringe needle. If your impulse tube will enough long - pressure sensor will not damaged by high temperature.
You may use lower temperature sensors if you have a connection long enough to allow a consistent heat transfer to ambient and cool the fluid in the tube. The problem is that the tube content, its elasticity under pressure, the bulk module of the fluid and the cavity volume where you place the sensing element build a low pass filter. If you have in the main circuit fast changes (important dp/dt) they will NOT be correctly recorded.
Which is the fluid you heat and want to measure?
Suggested needles are of course OK but only if from the dynamic point of view you have a steady state to analyse. For the tube length you should as well consider heat conduction which implies a longer tube and leads to a lower cutting frequency.
Consider also the possibility to measure pressure via the channel wall deformation with a calibration at low temperature. In this case you can use other sensors as displacement which are with no contact to the wall en thus insensitive to temperature.
Dear mr. Najeeb! Pay attention to the advice of Mr. Nick, he is very correct. The rate of pressure change is important when using impulse tubes.
In addition, if a burning gas or a moist gas moves in your channel, then moisture can condense in thin impulse tubes. If the pressure in the channel is small (up to 100 Pa), the condensate in the impulse tubes can lead to errors.
I may add the dynamic impact of the condensation mentioned by Mr. V.A. Kapitanov.
If the condensate builds up a "plug" its mass, the wall friction and the effects of the superficial tension will add a supplementary braking effect and reduce even more the cutting frequency.
If you give more detailed information about the fixture and fluid the answers can be more centered on your real problem.
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