Calculating Volumetric Flow Rate Without Cross-sectional Area

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Discussion Overview

The discussion revolves around the question of whether it is possible to calculate volumetric flow rate without knowing the cross-sectional area of the flow. Participants explore various types of flow meters and their operational principles, including theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks if volumetric flow rate can be calculated without knowing the cross-sectional area, referencing a portable thermometer that displays flow rate without this information.
  • Another participant inquires about the specific type of flow meter being discussed, indicating that the type of device is crucial for understanding the question.
  • Several participants suggest measuring the flow by collecting it in a container and timing the collection, questioning whether the original inquiry is theoretical or practical.
  • A participant describes a calorimetric mass flow meter that measures heat carried off by the flow, explaining that it outputs a signal proportional to flow rate without needing the cross-sectional area.
  • Another participant notes that true mass flow meters can measure mass flow rate directly and convert it to volumetric flow rate, mentioning the principles behind thermal flow meters and Coriolis mass flow meters.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of knowing the cross-sectional area for calculating volumetric flow rate. Some argue that certain flow meters can provide flow rate measurements without this information, while others seek clarification on the types of flow meters being referenced.

Contextual Notes

Participants highlight the importance of calibration and the specific operational principles of different flow meters, indicating that the discussion may depend on the definitions and assumptions related to flow measurement technologies.

Ehsans
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hi ,
I have a question that if you answer it I would be so thankfull, Q is:
"Can we calculate volumetric flow rate without knowing cross-sectional area?
If,yes,How?"

I have this Q because I see a portable Thermometer,volumetric flow rate meter ,which show it without giving any area size!

Thanks lot,
Ehsan
 
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What flowmeter do you have?
 
Collect what is flowing in a measured container and time it.

Is this a theoretical question, or an aplication for which you need a calculation or measuring method?
 
Artman said:
Collect what is flowing in a measured container and time it.

Is this a theoretical question, or an aplication for which you need a calculation or measuring method?

Hi artman,
I want to know how it works,maybe Theoretical or aplication :)

thanks ,
Ehsan.
 
FredGarvin said:
What flowmeter do you have?

Hi Fred ,
I haven't it , just saw it in university.

thanks,
Ehsan.
 
You really do not provide enough information to enable a meaningful answer. What kind of flow meter are you talking about?

I am currently working with ftp://ftp.captor.com/docs/Datasheet_4311-30-US.pdf[/URL] it is a calorimetric mass flow meter, that is it measures the amount of heat carried off by the flow. The output is a 4-20ma signal which is proportional to the flow rate. Internal electronics "know" the physical parameters about the flow meter, so I do not need to.
 
Last edited by a moderator:
The whole point of the flow meter is to give you the flow rate. Granted, proper calibration is a must, but that is the point of the instrument. Rephrase your question so we can better understand what it is you are looking for.
 
I am a bit late. Actually true mass flowmeters can directly measure mass glowrate and then it will be converted to volume flowrate. Thermal flowmeters based on calorimetric principle, as suggested by Integral, measure mass flowrate by sensing increase in temperature as heat flows from a resistor to the flowing fluid. The simple equation used is Q = mxCpxdT. Q is the constant heat flowrate supplied by the resistor, m is mass flowrate of fluid, Cp is its specific heat and dT is temperature difference.

Corriolis mass flowmeters measure the force exerted upon a sensor(based on the mass flowrate). These two devices don't require pipe size input. However, for better accuracy and lower pressure drops, a velocity range is specified.
 

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