Volumetric flowrate of one substance to another

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Discussion Overview

The discussion revolves around converting a measured leak rate of air through a valve into an equivalent leak rate for Jet A jet fuel. Participants explore the implications of different fluid properties and conditions, including temperature and pressure, in the context of fluid dynamics and leak rate calculations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a leak rate of 0.046 lbs/min of air and requests assistance in converting this to a leak rate for Jet A jet fuel, providing relevant parameters such as temperature and pressure.
  • Another participant suggests that mechanical engineers are capable of handling this type of problem and references a document that outlines procedures for converting leak rates from gases to liquids.
  • A later reply clarifies that the conversion is not simply from gas to liquid of the same substance but involves estimating the leak rate for a different material based on the test results with air.
  • One participant proposes using conservation of mass or momentum equations, mentioning Navier-Stokes equations as relevant to solving the problem.
  • Another participant emphasizes the importance of knowing the dynamic viscosity of the fluids and the pressure differential across the leak to estimate leakage rates, regardless of whether the fluids are in different phases or entirely different substances.
  • One participant suggests using Bernoulli's equation to find nozzle efficiency based on the size of the leak and pressure, and then applying it to the other fluid.

Areas of Agreement / Disagreement

Participants express differing views on the approach to converting the leak rates, with some focusing on fluid properties and equations while others emphasize the context of the materials involved. No consensus is reached on a definitive method for the conversion.

Contextual Notes

Participants mention various equations and principles, such as Bernoulli's equation and Navier-Stokes equations, but do not resolve the specific mathematical steps or assumptions required for the conversion process.

CTTKDKing
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Basically we have a valve that was tested with air and gave us a leak rate (MFR) of 0.046lbs/min of air. We need to know how much that equates to in Jet A Jet Fuel. The stats are: temperature ranging from 120 F to 200 F. Fuel temperature will range from -40F to 150F. Air pressure in the line will range from ~ 20-40 psig. Fuel pressure could be as high as 10 psig. Density of Jet A jet Fuel is about 6.7 lbs / Gallon US.

Does anyone know how to figure out this conversion. Ask me any more info required and i'll see about getting it. Most of the people working on this are mechanical engineers and are not really good with this type of problem.
 
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CTTKDKing said:
Basically we have a valve that was tested with air and gave us a leak rate (MFR) of 0.046lbs/min of air. We need to know how much that equates to in Jet A Jet Fuel. The stats are: temperature ranging from 120 F to 200 F. Fuel temperature will range from -40F to 150F. Air pressure in the line will range from ~ 20-40 psig. Fuel pressure could be as high as 10 psig. Density of Jet A jet Fuel is about 6.7 lbs / Gallon US.

Does anyone know how to figure out this conversion. Ask me any more info required and i'll see about getting it. Most of the people working on this are mechanical engineers and are not really good with this type of problem.

Actually Mechanical Engineers are really good at this type of thing.

However, you can find the procedure for converting leak rates from gases to liquids on page 64 of this document:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680010920_1968010920.pdf

Hope this helps.

CS
 
stewartcs said:
Actually Mechanical Engineers are really good at this type of thing.

However, you can find the procedure for converting leak rates from gases to liquids on page 64 of this document:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680010920_1968010920.pdf

Hope this helps.

CS

Actually I meant electrical engineers, lol sorry about that.

It was tested with air, and now we need to know how much will leak through the same valve with Jet Fuel. It's not a matter of converting from a gas vapor to the same substance in liquid form, it's a matter of going from one material and based on the test results with that one material getting a measurement for the other material, if that makes sense. Thanks for any help that has been or can be offered.
 
CTTKDKing said:
Actually I meant electrical engineers, lol sorry about that.

It was tested with air, and now we need to know how much will leak through the same valve with Jet Fuel. It's not a matter of converting from a gas vapor to the same substance in liquid form, it's a matter of going from one material and based on the test results with that one material getting a measurement for the other material, if that makes sense. Thanks for any help that has been or can be offered.

You just need to use conservation of mass or conservation of momentum equation to solve this problem, remember navior stroke's equation to solve this. This question is very similar to my last week's homework question.
 
CTTKDKing said:
Actually I meant electrical engineers, lol sorry about that.

It was tested with air, and now we need to know how much will leak through the same valve with Jet Fuel. It's not a matter of converting from a gas vapor to the same substance in liquid form, it's a matter of going from one material and based on the test results with that one material getting a measurement for the other material, if that makes sense. Thanks for any help that has been or can be offered.

Doesn't matter...it can be the same fluid in different phases (i.e. gas or liquid) or it can be an entirely different fluid (i.e. air and jet fuel). You just need to know the dynamic viscosity of the fluids (which is indicative of the density of the fluid) and the pressure differential across the leak under test conditions.

Take a closer look at the link I posted and the relative equations (perhaps read back a few pages). There is a procedure to estimate the liquid leakage rate based on a known gas leakage rate.

CS
 
If you know the size (cross sectional area) of the leak and the pressure, bernoulli's equation will help you find the nozzle efficiency. Then apply Bernoulli's equation again to the other fluid, using the nozzle efficiency you just calculated.
 

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