Learning Forum

[soneill]

Has anybody had much success with calculating the CV of valves ? 

I can get calculations to work in the results section but the units seem to be off. I am double checking the equations to make sure units and order of magnitude is correct. Values I get are 150% too high. Geoetry scale imported is correct.

 

I'm also looking to capture this process in the ACT app builder too!

 

If anyone has any suggestions or recommendations that would be great. 

 

My method: 

Flow inputs:

20D upstream and 7D downstream

Mass flow inlet 40 kg/s

Pressure outlet: 997.7 kPa

Wall boundary

med-high mesh

Results:

Two planes created to capture deltaP

    1st Plane at 18D upstream

    2nd 1D Plane downstream

Calculation for deltaP executed

Calulation for Volumetric flow calculated form MassFlow

 

Cv eqaution then calculated. Please see images to help explain in more detail. 

 

The pressure drop should be 1 PSI or 6.89kPa or 0.00689MPa for a given flow to achieve Cv value. In the pictures the pressure drop is lower than 1 PSI and the CV calculated is 841 (750 expected as from physical testing)

 

Other than that maybe my geometry is wrong. 

 

Thanks for your help     

[Naresh Patre]

Hello soneill

Can you share the AIM project file (archived .wbpz file)?

[soneill]

Here you go

https://drive.google.com/file/d/1tJz4oKpLfAa_ArYg8e7zrCBBE6bopmxc/view?usp=sharing

[Naresh Patre]

Hello soneill

I am not able to access the google drive path due to some reasons. I will send you a secure transfer link through email using which you can send the file.

[Naresh Patre]

Hello soneill

Thanks for sending the file. I reviewed it and below are my observations:

1. The mesh seems to be too coarse as seen in the image below. I noticed that you have set the Solution Fidelity option to an extreme low. This will give you a very coarse mesh and reduce the accuracy of results. Please increase the mesh resolution so that you have reasonable mesh in the geometry. 

 

2. There are some steps in the geometry near the converging - diverging section of the pipe. Are the steps important in your simulation? If yes, then you need to have refined mesh to capture all the geometry details. If not, please clean up these geometry steps.

 

3. In your problem description, you mentioned that Mass flow at inlet is 40 kg/s. However, in the simulation you have specified mass flow as 135 kg/s. So please review your boundary conditions.

4. For units of Cv, please refer to this discussion thread.