4 replies to this topic

[Process Engineer_DES]

Hello,
I have a question regarding the topic of equivalent length. Le donates equivalent length. then what does Le/D donate? what is the significance of Le/D as a whole? Le is used for calculation of pressure drop, but what does Le/D stand for and its importance?
Thank you. Waiting for someone to answer.

[breizh]

http://www.engineeri...thod-d_804.html

Hi ,
This question is a very basic one and I would advise to find text book on fluid dynamic.

Let you try to get a copy of Crane TP 410.



Breizh

[ankur2061]

Athar,

Read the article on "Cheresources" provided as a link below:

http://www.cheresour.../eqlength.shtml

Regards,
Ankur.

[katmar]

Dividing the equivalent length Le by the pipe inside diameter (i.e. D) is a very useful concept because for a given type of fitting - say a long radius elbow - the ratio Le/D is virtually constant. This means that you do not have to tabulate and remember Le values for every different size available. You need only to remember the Le/D ratio for the type of fitting and then you can get the Le by multiplying by the actual pipe ID.

The alternative to using Le/D values is to use the resistance factor, or K-Value. If you use accurate K-Values that is probably the best way to go, but the difficulty is that K-Values vary with Reynolds number and with pipe size. On the other hand the Le/D ratio is almost constant for all Reynolds numbers and all pipe sizes. When you consider that the K-Value (and the Le/D ratio) for a typical fitting like a reducer will vary from manufacturer to manufacturer by 50% or more, and even within a batch from the same manufacturer, it is a fruitless exercise to try to be too accurate in calculating the pressure drop through fittings.

[Padmakar Katre]

it is a fruitless exercise to try to be too accurate in calculating the pressure drop through fittings.

Hi,
Well explained in case of revamps you have the isometrics available for accuracy to maintain and in case of grass root design you can keep some safety margins.