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Gravity Flow


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#1 ashishmishra1234

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Posted 08 June 2015 - 11:57 AM

Dear Memebers

 

I want to calculate the flow through vertical pipes as attached, problem is the flow from A and B should be same with out creating any turbulence in the tank even they are fitted at different levels . Please give me your experts advice so that i proceed.

 

Thanks

 

Ashish

Attached File  Flow from tank.xls   67.5KB   56 downloads



#2 Zauberberg

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Posted 08 June 2015 - 01:53 PM

Type "gravity flow" in the search window of ChE Forums. There is a plenty of spreadsheets, articles, and discussions on the subject.

The download section of ChE Resources contains Excel spreadsheet on gravity flow.



#3 ashishmishra1234

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Posted 08 June 2015 - 10:27 PM

Dear zauberberg

The problem is bit different as discussed later in this forum. Please look into it the container have one inlet and two outlets as in attached. Need equal flow form each outlet. Want to calculate the sizes of outlets.

#4 breizh

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Posted 09 June 2015 - 12:20 AM

Ashish ,
You should show us your work for us to support you .

I guess you can write a few equations about your system (continuity, static head should compensate the head losses) .

Hope this helps

Breizh

#5 Linda1978

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Posted 09 June 2015 - 12:36 PM

If the problem is sizing gravity lines use available software and webpages

 

usually the liquid line sizing for a gravity flow is performed based on criteria of 0.035 bar / 100 m. you can simply develop your own excel sheet and find the proper size. \

 

Good Luck



#6 samayaraj

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Posted 10 June 2015 - 05:49 AM

Ashish,

 

I have the following query to understand your problem better.

 

1. The outlet lines A & B are terminating at the same elevation where the water level is maintained?

2. Your intention is to maintain the water level constant by overflowing equal flow in both the lines?



#7 ashishmishra1234

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Posted 10 June 2015 - 05:58 AM

Yes Mr Samayaraj , the intention is to have equal flow from both pipes by maintaining water level constant.

#8 katmar

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Posted 11 June 2015 - 03:33 AM

The first question you need to ask yourself (and try to answer!) is what would make the flow rates different from each other.



#9 juche

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Posted 11 June 2015 - 06:03 AM

Ashis

 

i feel the flow rate will be always be same for both the pipes if they are of same size.

 

As it is a U tube the Hydrostatic heads will equal on both side and it will be neutralized the elevation (as shown in figure 5 and 10 m) will not make any difference to flow.

 

Yes if some different size of pipe is selected for both the pipes the flow may differ minutely due to different frictional losses which will be negligible.


Edited by Jutesh, 11 June 2015 - 06:05 AM.


#10 samayaraj

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Posted 11 June 2015 - 03:00 PM

Ashish,

 

Water level will be slightly higher than the terminal elevation of both pipe to accommodate the pressure drop taking place in pipe and in the entrance of pipe tapping. Let it be "H". (As linda said, you can keep 0.035 bar/100m as drop for your problem)

 

Here, pipe B length is more than pipe A. Hence, for the equal flow rate and same dia of pipe, pipe B will have slight more pressure drop than pipe A and for the same dia of pipe, you cannot get the equal flow rate in both pipes. For this, pipe B dia need to be increased little to match the same flow rate in pipe A. You can simply do calculation in excel by using below reference.

 

For both the pipes,

 

VA2/2g + h A loss = H = VB2/2g + h B loss

 

where,

 

A loss , h B loss head losses in pipe A & B.

(h A loss,  B loss= drop due to pipe + bend + entrance loss)

V& VB are the velocities in pipe A & B.

 


#11 ashishmishra1234

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Posted 12 June 2015 - 07:54 AM

Thanks Samayaraj

 

I will do this

 

 

Ashish



#12 ccjayesh

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Posted 29 June 2015 - 05:03 AM

Hi Ashish,

Samayaraj's Explanation is theoretically true. But if u have to apply it in an industry, u may not able to find a standard pipe size for correcting such a minute difference in velocity.






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