8 replies to this topic

[panoska]

Hello everyone,

I was reading somewhere that the K value (resistance coeffecient) for tees can be negative. What is the reasin for that?

[breizh]

Hi,
weird, share the references.
Breizh

[panoska]

Hi Breizh,

It is weird? I cannot find the reference anymore!
That's why I am asking in case someone is aware of it.

Maybe the interpretation of negative is that
it goes to higher energy.

[latexman]

It is so in my 2018 version of Crane Technical Paper No. 410.

 

Energy is added to the slower moving fluid accelerating to the velocity of the total combined flow.

[panoska]

Hi Latexman,

I will check the Crane for more infos!

You are referring to the case of mixing, right?

[latexman]

Negative K value is a larger effect when both flows converge, but IIRC it is present to a lesser degree in one of the two diverging cases too. See Crane TP # 410.

[breizh]

consider this link,
https://www.google.c...ZDSwL4dPFLpgHFm

 

Note : Get a copy of "pipe flow a practical and comprehensive guide " by Rennels and Hudson for full explanation. 

 

Breizh

[fallah]

Hello everyone,

I was reading somewhere that the K value (resistance coeffecient) for tees can be negative. What is the reasin for that?

 

Hi,

 

The key point is pressure loss coefficients in tees are more impacted by flow distribution than velocity and diameter.

Then mixing flows in tees could result in negative pressure loss coefficients, which is due to a negative pressure created by the momentum of the large inlet flow.

[panoska]

Hello everyone,

Thank you for your explanations!