10 replies to this topic

[renjith553]

Hi,

 

I am in the process of designing a 2 m3 buffer tank install on water loop to break the loop pressure to facilitate the addition of treated water from RO units. The flow rate is as given below.

inflow - 250m3/hr

outflow - 250m3/hr.

As the flow is high , I will have the issue of Vortex..So I would like to know , what are the parameters I need to consider while designing it to avoid vortex formation.. 

[Lai.CY]

Hello Renjith,

 

Have you considered using a vortex breaker on the liquid outlet?

[markymaark]

Or internal baffles.

[renjith553]

Hi  Weiiskruez/  Marky Maark,

 

Yes , I am planning to put a Vortex breaker on the outlet nozzle.  But little bit confused about , how to design the best one for my application.. Right now , I thought of putting a normal cross shaped Vortex breaker welded at the entrance of the outlet nozzle..  Following are the other considerations I have taken.

1) I  calculated the minimum submergence height based on the outlet nozzle flow to the pump and kept it as my   low level for the tank to trip of the pump.

 

But I didn't consider the effect of the 250m3/hr of inflow that is coming in to the tank through inlet drop tubes ( 3 numbers).. so I am bit worried , whether this will accelerate the vortex creation, when i am near my low level in the tank.. 

 

Also will baffles help me in some way?  If Yes what type of baffles I need to go for..

 

Thanks in advance for your expert advice..

 

Renjith.

[Lai.CY]

Hello Renjith,

 

I think it'll be great if you could share more details, such as you pipe size, tank dimension, etc. So that others with similar experience can share their views.

With just the flowrate information, we can only assume/guess that your outlet velocity might be too high, you should increase your minimum low low liquid level (what is your current liquid level?), installation of calming baffles (perforated plates), and so on. While I have always seen the usage of simple vortex breakers on liquid outlets with a low low liquid level typically at ~150-200mm from bottom of vessel, I've not heard from other discipline's feedback that we have any gas bubble carry under with the liquid phase, just minor surface swirls, perhaps I deal more with oil (higher viscosity) and not much on pure water.

 

I apologize that I couldn't be of any help.

[markymaark]

There are many different types of baffles.  It's a quite easy solution.  However, if you are retrofitting this tank then you may have issues.

 

See the link below for a thorough report on baffles used in tanks to prevent vortex.

http://www.postmixin...les/baffles.htm

 

As post#5 said, knowing more of your application may help.  Is this JUST for RO water and pressure reduction.  Existing tank to be retrofit, or new tank design?

[renjith553]

Hi,

 

Please find attached , the initial design of the tank..   It will be a  brand new tank..  Now with this attachment I feel my question will be more clear..

 

I have calculated the minimum submergence required  and I got around 0.9 m which is pretty high..  I want to reduce it to the minimum possible ..  

 

The buffer tank concept is just to facilitate the connection of RO water to the loop without the  problem of varying back pressure..  

 

    

Regards,

Renjith.

Attached Files

•  Tank-design1.xlsx   53.92KB   82 downloads

[Marian1]

Ren,

design the outlet nozzle for 1 m/s velocity and put a standard cross-shaped vortex breaker.

There will be negligeable vortex depression.

Put the LLL switch setpoint at 200 mm (250-300 in  in case of thick wall vessels, requiring a higher welding line) above the tangent line.

[Dedi]

you can install your buffer tank diagonally to minimize the vortex. hope this helpfull

[breizh]

http://www.google.co...iw=1081&bih=592

 

Consider this resource

Breizh

[renjith553]

Thanks all for your valuable inputs... I have taken the final model for CFD.. Will keep you updated with the final result... :-)