3 replies to this topic

[Erica789]

Background: There are 12 tangential entry to wiped film reactor.pressure in the reactor is 50mmHg vac.(710 mmHg abs.)

 

i have to design distribution system such that equal flow goes through each entry

 

i am stuck and confused where to begin with.

what should  be the pressure at which it should enter so that it forms uniform film and also does not splash without forming film.

is there any mathematical model or reference paper to design same

[thorium90]

Such a complicated flow system might be better simulated with CFD.

[Bobby Strain]

You will likely need to provide control valves to each.

 

Bobby

[Saml]

You are asking two questions as I understand it:

 

- The first is how you make both flow to be similar. The way to do it is that the pressure drop at the entry point is the main pressure drop in your system and to ensure that on both inlets is equal at the same flow.

 

- On the second, the velocity and the way it should enter is very application specific since it depends on the rheology of the fluid, the way it wets the walls, the foaming tendency of the fluid, the presence of bubbles, etc, etc. As someone mentioned above, CFD is one way. Bench tests is another. But you should take into account that just a weld may cause the film to separate from the wall.

 

My experience on these type of distributors is that it is not easy at all (not exactly for a wiped film reactor, but a falling film  evaporator in one in one case and a separator with tangencial inlets in another).

 

- On one case, the distributors had to be modified at least 3 times. Always by the supplier. They finally got it working. But I felt that they were learning with a full scale plant experiment paid by our company. As far as I know, they used CFD but still went thru three iterations until they have it working right.

 

- In the other case, the internals had to be repaired every time we opened  the vessel. Maintenance people kept reinforcing the internals and looking at Process Engineers with that face of "what do we do now?". As far as I know (I don't work in that place now) they still have this problem. Some proposal that the engineering company implemented in other plants included a desing with specially built pieces of pipe (tapered, varying radius and plane curved piping). It was a CFD desing, but with no guarantee, so the decision at the time was wait and see.