• #### Perforated Pipe Pressure Drop

From ksepehrinia@gmail.com@21:1/5 to CKruger on Tue May 24 02:00:17 2016
On Tuesday, June 3, 1997 at 11:30:00 AM UTC+4:30, CKruger wrote:
Dear Ben

From you email address I see you are from Amoco, and even though I
have never worked for them, I can bet my right arm that there will be
someone in Amoco (actually more than one) that knows more than me
about distributors. But anyway, here goes.

It depends on what the distributor is for, for example:

1) Equal distribution between all holes. In this case the pressure
drop across the holes must be high enough compared to the pressure
drop through the pipe (I think a guy called Simpson wrote an article
on this quite some time ago, and he is also quoted in Perry). An easy guideline that I have seen is to make the hole velocity twice the pipe velocity, with some upper limit on hole velocity (say 10 ft/s,
although some companies will limit it to 4-5 ft/s in some cases) to
prevent excessive turbulence/disturbances. The pressure drop thru the
hole can be calculated with the normal orifice equations, which are
normally simplified for this application and exclude any pressure
recovery term. A special case is maybe very long distributors such as
for irrigation. I would tend to do a detail pressure drop analyses
over the entire pipe for such cases.

2) Proper entry into vessel. The idea here is to put the liquid/vapor
into a vessel with minimum turbulance to improve phase separation,
etc. Here an easy guideline is to make the total hole or slot area
twice the pipe area.

3) Proper contact. Sometimes you want to limit the drop size to
enhance interphase transport/extraction. I don't know what the maximum
is, but I have often seen sizes in the range of 10 mm (0.5 in ID) and smaller.

Hope it helps
Christiaan

Ben Walker <zbjw17@amoco.com> wrote:

Has anybody got anything on pressure drop/flow distribution for
perforated pipe flow distributors. I looked in Perry's and they only had >a brief blurb and a formula for pressure drop that doesn't work with any >length/diameter. Any help would be appreciated. Thanks.

Ben

I want to calculate the pressure drop in a perforated pipe which is responsible for distributing a two phase flow in a stripping tower. The vapor volume flow rate is 68% of total flow rate. Perforated pipe diameter, the holes quantity and their diameter,
vapor and liquid phase flow rates, their composition and density are known. Please let me know how can I calculate the pressure drop? (specially pressure drop through the holes) It would be appreciated, if you could introduce me a reference (or a few
good references) as well.

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• From Lynn McGuire@21:1/5 to ksepehrinia@gmail.com on Wed Jun 1 15:15:36 2016
On 5/24/2016 4:00 AM, ksepehrinia@gmail.com wrote:
On Tuesday, June 3, 1997 at 11:30:00 AM UTC+4:30, CKruger wrote:
Dear Ben

From you email address I see you are from Amoco, and even though I
have never worked for them, I can bet my right arm that there will be
someone in Amoco (actually more than one) that knows more than me
about distributors. But anyway, here goes.

It depends on what the distributor is for, for example:

1) Equal distribution between all holes. In this case the pressure
drop across the holes must be high enough compared to the pressure
drop through the pipe (I think a guy called Simpson wrote an article
on this quite some time ago, and he is also quoted in Perry). An easy
guideline that I have seen is to make the hole velocity twice the pipe
velocity, with some upper limit on hole velocity (say 10 ft/s,
although some companies will limit it to 4-5 ft/s in some cases) to
prevent excessive turbulence/disturbances. The pressure drop thru the
hole can be calculated with the normal orifice equations, which are
normally simplified for this application and exclude any pressure
recovery term. A special case is maybe very long distributors such as
for irrigation. I would tend to do a detail pressure drop analyses
over the entire pipe for such cases.

2) Proper entry into vessel. The idea here is to put the liquid/vapor
into a vessel with minimum turbulance to improve phase separation,
etc. Here an easy guideline is to make the total hole or slot area
twice the pipe area.

3) Proper contact. Sometimes you want to limit the drop size to
enhance interphase transport/extraction. I don't know what the maximum
is, but I have often seen sizes in the range of 10 mm (0.5 in ID) and
smaller.

Hope it helps
Christiaan

Ben Walker <zbjw17@amoco.com> wrote:

Has anybody got anything on pressure drop/flow distribution for
perforated pipe flow distributors. I looked in Perry's and they only had >>> a brief blurb and a formula for pressure drop that doesn't work with any >>> length/diameter. Any help would be appreciated. Thanks.

Ben

I want to calculate the pressure drop in a perforated pipe which is responsible for distributing a two phase flow in a stripping tower. The vapor volume flow rate is 68% of total flow rate. Perforated pipe diameter, the holes quantity and their
diameter, vapor and liquid phase flow rates, their composition and density are known. Please let me know how can I calculate the pressure drop? (specially pressure drop through the holes) It would be appreciated, if you could introduce me a reference (or
a few good references) as well.

Is the pipe capped?

I would guess that each hole can be treated as an orifice?

Lynn

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