Pressure Drop through 135 degree tee 2

[datsnl]

Hello,

I am using Crane technical paper 410 for calculating pressure drop but I am not able to find pressure drop for 45 degree or 135 degree tee. Can anyone help?

Also, I would like to know, what will be pressure drop of the mitre bend if it is a 2 cut or 3 cut mitre? Crane Technical Paper 410 only gives pressure drop for 1 cut mitre.

Cheers

 

[Yorkman]

Would a three cut miter be equal to the pressure drop of two 22.5 single cut miters?

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[datsnl]

I am not sure, but as far as I know, the calculation given in Technical Paper 410 suggest that there should be 1D spool left before and after the mitre cut, but in real practice when we use a 2 cut mitre or a 3 cut mitre, 1D before and after the cut is never achieved and so I doubt that multiplying the pressure drop of two 22.5 single cut mitre might help. But if you have better reasoning than this, please let me know.

Also in Crane technical paper 410 they give pressure drop for cut angle in the range of 0, 15, 30, 45, 60, 75 and 90 degrees, and it is not mentioned that for cut angle between the values mentioned in the paper, we can use interpolation. If you have another source that gives pressure drop for 22.5 cut, I would be glad to have a look at it.

cheers

 

[Yorkman]

Sorry disregard that post I misinterprited your description of two cut and three cut. We always refered to them as 2 piece (1 cut) and a three piece (2-cut)90s. I'm sorry to say I've not seen any data on pressure drop or equivalant pipe lengths for these type of fabricated fittings.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[datsnl]

Sorry for my way of explaining the problem. There are various methods of saying a technical word in a non technical way and the most you prefer is the one that is used in the place you work. Here they call mitre bends as lobster back, but i refrained from using that term.

cheers

 

[Yorkman]

Now that's one I haven't heard, the closest we get to marine life is a 90 degree saddled tee calling it a fish mouth.
In regards to the pressure drop vales I think I've got the same table giving "K" factors for the very same angles you had listed, sorry nothing more.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[katmar]

K values for mitred bends (which are also referred to as lobster backs here in South Africa) are given by the 2-K method proposed by W.B. Hooper in Chem Eng, Aug 24, 1981.

Darby's 3-K method (Chem Eng, April 2001) also has data, but comparing his values with Crane 410 leads me to believe that Darby has confused the K values per cut with those per 90 degree bend.

For fully developed turbulent flow I would use the following K values

1 weld, 90 degrees K = 0.85
2 weld, 45 degrees K = 0.44
3 weld, 30 degrees K = 0.34
4 weld, 22.5 degrees K = 0.32
5 weld, 18 degrees K = 0.30

For comparison, the K value for a 1.5 radius 90 degree pipe bend would be 0.21

I do not have any data for your 135 and 45 degree Tee's.



Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Yorkman]

datsnl,
Guess what, while searching through an old reference on centrifugal pumps I think I've found the data "K" factors for 45/135 degree laterals that you were looking for. The K values are listed in a nomograph, and vary depending on the path of flow through the fitting. It did not provide any values changes if the lateral was reduceing in nature.
Here are the "K" values hope they work for you;
(A) Staight flow through main of lateral: .15
(B) Flow going through lateral exiting main: 1.0
(C) Flow going through lateral entering main: .5
As a check/verification the graph plots,:

(A) style 20" lateral has an equivalent pipe length 9 Ft

(B) style 20" lateral has an equivilant pipe length 60 Ft

(C) style 20" lateral has an equivilant pipe length 30 Ft
The author did not reference who produced the graph. If I see anything else I'll post.


I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[datsnl]

Thanks guys,

Sorry for being dumb, but the K values provided by Katmar and Yorkman are the one that can be used directly in the formula

PD = K * (V^2 / 2*g) where PD is Pressure Drop V is velocity and g is gravitational acceleration.

Correct me if I am wrong.

Thanks

Dharmit

 

[Yorkman]

Dharmit,
That's correct I believe your PD will be in Ft/Hd loss according to my reference, not in psig. Multiply Ft/Hd by .433 to get to psig. Also changes in liquid density may affect this formula but for general purposes it will probably very only slightly. The ASHREA Fundamentals Handbook Chapter 36 (pg.36.1)has formulas that account for changes in density, you might want to check out.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[datsnl]

It depends which units you consider.

If I take velocity in m/s and gravitational acceleration in m/s^2 then the units of PD will be in meter, as K is not having any units, its dimensionless.

Then to get the PD in Pascal use the formula

PD(Pascal) = Density of fluid (kg/m^3) * gravitational acceleration (m/s^2) * PD(m).

Old University days are back. I hope my rusty mind have generated correct formulas. correct me if I am wrong.

Cheers

Dharmit
Hatch Associates

http://www.hatch.com.au

 

[Yorkman]

Dharmit,
Sorry I made that rude assumption that the world is flat, milk is sold by the gallon and potatoes by the pound!! I need to bone up on my SI units and start thinking in broader terms. I don't feel comfortable commenting on your units at this point in time.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[katmar]

Dharmit,
Yes - your units are correct.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[datsnl]

Thanks guys,

This was fun, Thanks for your help and research. This will be helpful to me.

Cheers

Dharmit
Hatch Associates

http://www.hatch.com.au

 

[katmar]

Yorkman,

I am interested in your data for the 45/135 degree Tee, but I don't quite follow your A, B and C descriptions. The terminology I would normally use is the "run" for the section that goes straight through, and the "branch" for the piece that sticks out the side of the run. If you think of a letter "T" the run is the piece across the top, and the branch is the piece sticking down. How do your "main" and "lateral" compare with these descriptions?

I would expect the 45 degree side to give different behaviour from the 135 degree side. Does your data distinguish bewtween the two possible flow directions? For flow through the "run" of a normal (symmetrical) pipe tee I use a K value of 0.045, and a value of 0.74 for flow from the run to the branch.

Please can you also give the reference where you found this data - I have access to quite a bit of old data and I may be able to find it here.

Thanks very much
Harvey

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[datsnl]

Harvey,

I think I am awaking from my winter sleep, but the values given by you for the k values for Mitre bend is for a single mitre. Wait let me make it more clear.

If I want to use 90 degree mitre bend with 3 weld, I have to use 3 * 0.34 = 1.02 for the value of k.

Correct me if I am wrong.

"My teacher used to say that I was a slow learner".

Cheers

Dharmit
Hatch Associates

http://www.hatch.com.au

 

[Yorkman]

Katmar,
the lateral term I'm using is the branch sorry about the confusion in terms. The 45 degree branch with the flow leaving the run has a "K" value of 1.0. The 45 degree branch with the flow entering the run has a "K" value of .5 The "K" value for the run is .15, it did not matter what direction the flow was through the run I guess as they only supplied one value.
As I mentioned in the ealier post the "K" values come from a "nomograph" and they didn't provide any data on a reduced branch configuration, and they only list the single set of "K" values if you know what I mean.

The book that I found this in is titled:
Centrifugal Pumps Selection, Operation, and Maintenance
by: Igor J. Karassik and Roy Carter
Publisher McGraw-Hill Book Company 1960

PS:Igor Karassik was a consulting engineer for Worthington Corporation if it helps.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[katmar]

Dharmit, the K values I gave are for the full 90 degrees so it is not necessary to multiply by the number of welds. Think of it as a gradual approach to a smooth bend, which has a K value of 0.21. Each time you add in a weld you reduce the overall K value for the bend because it gets closer to being a smooth bend.

Yorkman, thanks very much for the clarification and for the reference. I will look around for a copy of that book here.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[datsnl]

That makes sense. Infact a lot of sense now...........

Cheers

Dharmit
Hatch Associates

http://www.hatch.com.au

 

[Yorkman]

Katmar,
I found a copy of that book on line here's the URL:

http://www.amazon.co.uk/exec/obidos/Author=Karassik, Igor J./-30k

It's the book with the printing edition Dec. 1960

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI