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Approach In Co Current Flow Shell And Tube Hear Exchanger


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#1 S.R.Shah

S.R.Shah

Posted Yesterday, 05:23 AM

I want to keep outlet temperature of process steam coal seam to cooling water outlet temperature using co current shell and tube heat exchanger considering sacrifice in LMTD.My question is how much practical approach should be consider in co current heat exchanger.For example if we assume 5 deg C as approach limit for counter current shell and tube heat exchanger,what shall we achieve in co current heat exchanger.What are other alternatives in design other than co current heat exchanger
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#2 Zauberberg

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Posted Yesterday, 01:21 PM

Which exchanger type and what configuration you are using? Please submit more information about the application.


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#3 S.R.Shah

S.R.Shah

Posted Yesterday, 10:56 PM

Single pass shell n tube heat exchanger BEM type
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#4 S.R.Shah

S.R.Shah

Posted Yesterday, 10:57 PM

My application is liquid liquid cooling.Cooling of liquid process stream by cooling water

Edited by S.R.Shah, Yesterday, 10:58 PM.

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#5 Zauberberg

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Posted Today, 01:48 AM

Without knowing stream flows, properties, inlet temperatures, allowable temperature rise for cooling water, allowable pressure drops, as well as other parameters/constraints immanent to the design, it is virtually impossible to provide you with any specific comment.

 

In general, 5 degC temperature approach is achievable in the co-current flow arrangement with liquid streams on the tube side and shell side of the exchanger. The exact dimensions and configuration of the exchanger will depend on the parameters mentioned in the first paragraph.

 

If you want us to be more specific, please supply all the necessary data for thermal design.


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#6 S.R.Shah

S.R.Shah

Posted Today, 04:07 AM

Thanks Zauberberg.I have asked General question to select co current in place of counter current shell and tube heat exchanger.
It is 85 % Sulfuric Acid cooling with cooling water inlet and outlet temperatures 34 and 37 deg c.process steam itemperature has to be limited by 42 or less
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#7 S.R.Shah

S.R.Shah

Posted Today, 07:13 AM

I have to still do thermal design of said STHE
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#8 Zauberberg

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Posted Today, 01:34 PM

I don't know all the details of this particular application, but having water-cooled S&T exchanger in this service might not be the best practice - for several reasons:

 

1) Inlet (distribution) temperature of cooling water (CW) varies all year-round due to changes of ambient conditions and/or water demand, hence it seems impossible to meet the design requirements in all cases. If I understood well, CW inlet temperature (probably for the summer case) is 34 degC whereas the Acid outlet temperature is limited to max 42 degC. The difference is only 8 degC which will result in very high CW flows (HTFS shows 7:1 flow ratio for Water:H2SO4) and you may be robbing other users in the CW network, and also end up with a very high surface area (length) of the exchanger.

 

2) For fixed tubesheet (BEM) design, you will likely have to place H2SO4 on the tube side and CW on the shell side due to corrosion/fouling management. For carbon steel tubes, maximum velocity in Sulfuric Acid service is limited to 1 m/sec. For SS316 this limit goes up to 2.5 m/sec. As well as the exchanger cost. All this applies if we are talking about concentrated Sulfuric Acid at moderate temperatures. If the case is about diluted and/or hot Acid, a very exotic metallurgy will be required.

 

I'd suggest to look for other solutions (air-cooled exchanger or a special plate and frame exchanger may be better options). Consult with the manufacturers - Alfa Laval, Tantaline, MECS, Ultramet, and please make sure you provide all the details.


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#9 Zauberberg

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Posted Today, 05:30 PM

N.B. I assumed certain inlet conditions for Sulfuric acid. Otherwise it would be difficult to perform any kind of analysis.
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#10 S.R.Shah

S.R.Shah

Posted Today, 10:20 PM

Zauberberg

 

Thanks for  Analysis.

 

For this case ,I do not have chilled water and only to use Cooling Water.

 

Cooling Water Inlet temperature 340C is Summer Conditions

 

If Counter flow Current Heat Exchanger is chosen, Approach shall be more .For Cooling Outlet temperature 37 or 39 does have effect on LMTD  but marginal as Sulphuric Acid Outlet temperature is 420c. So area shall increase but in Marginally lower. Again Flow Rates are Smaller .

 

 

 

Whether in this Condition can one can go to Co-Current in place of Counter Current to keep Exit temperature of Sulphuric Acid close to

420C  ?

 

I have taken care of Material of Construction for this case.


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