Hello, I am looking for pressure drop equation for T and y pieces

[Markus1]

Hello everyone,

I am searching a formula for calculation of pressure drops in T- pieces and Y-pieces in piping installations.

What equation or factors can be used, if two identical streams enter the T-piece and hit each other from the front. I hope somebody can give me a rough idea.

Thank you very much, Markus

 

[samuelliu]

For Tee: you can find EQUIVALENT LENGTH from various papers, text books, manuals, and handbooks. There are three types of tee, and the EQUIVALENT LENGTH relationships among them are:

Straight Thro Tee : Flow Out Thro Branch : Flow In From Branch = 1 : 3 : 4.35.

 

[Markus1]

Hello Samuelliu,

thank you very much for your answer.
When I checked different sources of literature I found equivalent lengths differing between 2,0 and 21,0 for a 14'-Tee. This wide range is useless for an estimate.

Do you think the factor 4.35 for Flow In From Branch is a good approach, if two identical flows flow in from both straight through openings and exit through the branch with 90° change in flow direction? Is there an additional pressure drop if two flows enter the Tee from opposite directions?

Best regards, MarkusL

 

[zdas04]

From Crane 410, flow through a branch on a tee has a k=60*f(t). For 14" pipe, f(t) is 0.013 so k=0.78. Going to chart A30, you get an equivilent length of 70 ft when the flow streams head into each other.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

 

[fvincent]

A quite complete study on such coefficients can be found in:

Author : Idel'cik, I E;
Title : Handbook of hydraulic resistance : coefficients of local resistance and of friction

You can also find a French version: Mémento des Pertes de Charge.

fvincent

 

[ivp]

Try this site

http://www.fluidflowinfo.com

Excellent demo software.

 

[hydsim]

Hi all from this thread.
I have the same problem as Markus and I found some equations and tables in the following books:

Idelchik: Handbook of Hydraulic Resistance

Miller: Internal Flow Systems

Unfortunatelly, there are not anything for the few flow types(for example, symetric combining and dividing flow with angle less than 90°), so if somebody knows for other literatures about Tee and Y junctions, please inform me.

Regards,
Dino Mandic

 

[fvincent]

hydsim

Idel'cik memento does give a lot of data about junctions and bifurcations for several values of angle - at least my French version... Can you describe exactly the kind of singularity you mean?



fvincent

 

[hydsim]

Hi fvincent,

I have no data for backward combining and dividing flows as well as symmetric combining and dividing flow, if angle between pipe and side branch is less than 90 deg.

See below:

Backward combining flow:

----------------------------------
Pipe branch
<---- <---

------------ -----------
/ /
/ /
/ /
/\ side branch
/
/


Backward dividing flow:

----------------------------------
Pipe branch
----> --->

---------- -----------
/ /
/ /
/ /
side branch
/
/
\/

Symmetric combining flow:

----------------------------------
Pipe branch
----> <---

----------- -----------
/ /
/ /
/ /
side branch
/
/
\/

Symmetric dividing flow:

----------------------------------
Pipe branch
<---- --->

---------- -----------
/ /
/ /
/ /
/\ side branch
/
/

If there is equations (or data) for resistance coefficients (two coefficients in each case) for above cases in Idelchick which you have, please inform me.

Regards,
hydsim

 

[fvincent]

hydsim,

I must confess that I was wrong concerning how comprehensive is the Idel'cik work ... I am sorry: there is no reference to such cases as you have pointed...

I will try to get some information... 'cause I think I am in debt...

regards

fvincent

 

[stanier]

Idelchik covers this in Flow Resistance A Design guide for Engineers. There are a series of nomographs and charts.

No one procrastinated their way to the top

 

[lilliput1]

Don't get too hung up on decimals. Be safe & use the high loss value. Don't forget to add friction drop allowance for aging. Usi minimum 15% more for open systems & 30% to 75% more for open systems. The 75% will get you to about 30 years.

 

[fvincent]

hydsim,

Finally I got some information about pressure drop coefficients for some of the cases you've described.
You find curves for backward combining/dividing flow in the
VDI-Wärmeatlas, 5 edition 1998 - on pages Lc3 to Lc4.

I don't know if more updated edition have enhanced this chapter.

Some references are made to works conducted by Vogel and by Petermann. These are very old studies (1926 and 1929). I have no idea how to obtain copies of the original papers.

Hope this helps, anyway






fvincent

 

[arto]

Try D.S. Miller &quot;Internal Flow Systems&quot; from the BHRA:

http://www.bhrgroup.co.uk/confsite/infobook.htm#iflow