12 replies to this topic

[ezralh]

Hi,

 

I would like to calculate pressure drop between point A and B. Valve z is closed. What K-value should I used for tee? Crane Technical Paper No. 410 M, suggest  K = 60f_t for flow thru branch, however , since valve z is closed, all flow will be directed to B.

 

 

 

Attached Files

•  Cheres_tee_140420.JPG   12.76KB   1 downloads

[Bobby Strain]

Look for tee as elbow.

[ezralh]

Thanks Bobby.. that was what I did.. Just want to check with experts

[breizh]

Hi,

You should consider Mitre Bends with alpha = 90 degrees , K = 60*ft  as suggested

Crane Flows of fluids - TP No 410 M - page A-30

notes : 

There is an empirical formulation for Mitre Bend for alpha between 0 and 150 degrees 

           K= 0.42*Sin (alpha/2)+ 2.56 * Sin^3 (alpha/2)  from pipe flow a practical and comprehensive guide 

 same publication  : K=1.2  

 

Good luck .

Breizh

Edited by breizh, 14 April 2020 - 11:19 PM.

[latexman]

The 2018 Crane TP No. 410 (no M) has a more detailed method for tees and wyes than previous versions I've seen.  For a diverging 90^o tee with Q_branch/Q_combined = 1 (your case), K_branch = 1.7.

[Napo]

Ezralh,

 

From Perry, 7th edition. K = 1.0.

 

Napo.

Attached Files

•  CHAP06.PDF.pdf   762.71KB   24 downloads

[breizh]

Hi,

To add to my previous answers a picture extracted from KSB pamphlet : K  tee= 1.28 when  Qa/Q =1 together with another reference for tee  Akatherm (table 7.5 and fig 7.4 ) : K=1.3 where V0/Vt =1 

Last data : french document : K=1.2 ref  Miller .

Good luck

Breizh 

Edited by breizh, 18 April 2020 - 08:03 PM.

[sarinvaibhav161286]

The 2018 Crane TP No. 410 (no M) has a more detailed method for tees and wyes than previous versions I've seen.  For a diverging 90^o tee with Q_branch/Q_combined = 1 (your case), K_branch = 1.7.

 Hi Latexman,

 

In 2009 version of Crane, for Q_branch/Q_combined = 1  and A_branch/A_combined = 1  , the resistance coefficient of K_branch for 90 deg diverging Tee was 0.78.

Has it really increased to 1.7 in 2018 edition of Crane?

[latexman]

I just double checked.  They have an equation and a graph.  Both say K = 1.69.

[breizh]

Hi,

To confirm :

                    K branch for diverging flow in tees and wyes (Qbranch/Qcombined =1 ) , 90 degrees 

                     was equal to   1. 09  in 2010 

                     and 1.69 in 2011 ,

 

                     data extracted from  TP 410M  (metric version)

 

hope it helps .

 

Breizh 

Edited by breizh, 07 October 2020 - 06:55 AM.

[katmar]

@latexman and @breizh - nobody has mentioned the size or the geometry of the tee, nor any mention of the Reynolds number. Do your references mention any influence by these factors?  I would imagine that the k value for a small threaded tee would be higher than for a large welded tee with a well radiused inner surface.

[breizh]

Hi Katmar ,

Please review the document attached ( TP 410 M /2011) with different tables associated .

Note : probably good to take a look at Handbook of hydraulic resistance by I.E Idelchik to confirm .

 

Breizh 

Edited by breizh, 08 October 2020 - 06:24 AM.

[katmar]

Thanks Breizh.  It seems that Crane does not take the radius of the inner surface into account.  I compared these values with Idelchik (3rd Ed), but even though I have an English translation it is VERY difficult to read.  On page 438 (Diag 7-10) Idelchik gives K values for tees with sharp corners (same as the Crane diagram). The value is 1.86 for the case of flow from the branch to only one side of the run, and with all diameters equal. This is quite close to the Crane value of 1.7

 

On page 462 (Diag 7-23 No. 4) Idelchik has tees with radiused corners - the translator calls these "wyes of improved shape".  For r/D (corner radius / pipe diameter) of 0.22 Idelchick gives a K value of 0.8 and for r/D of 0.07 the K value is 1.0.  From these values the radius is important in the determination of the K value, and this certainly reflects my own experience.

 

These values give me reassurance in the Darby 3K method that I used in AioFlo.  For a sharp cornered 1" tee and a velocity of 1 m/s the 3K method gives a K value of 1.7 - in line with the Crane value.  But if we go to a typical forged or cast tee with radiused corners - and using 2 m/s in a 8" pipe - AioFlo gives a K value of 1.06.

 

These differences will not have a large impact in practice, but they do highlight the improved performance of more modern methods like 3K.