12 replies to this topic

[jaggu27]

I am a newbie to Process engineering. In my workplace we have a vessel with agitator. Now we want to cool the vessel contents by providing either jacket or limpet coil. For this we have calculated the total heat requirement and cooling water requirement. By applying the Nusselt number correlations I can find the area required in limpet coil side. Now with this area can any one please tell me the basis for choosing the coil size, and velocity of the cooling water. Also I want to know the effect of coil diameter. Kindly help me in this regard.

 

Thanks in advance

Jagadeesh

[latexman]

An existing vessel?  Is it already in the structure or is it on the ground/in the bone yard?  Will the vessel be sent to a shop for the limpet coils or will it be attempted in place?  Have you thought about a strap-on jacket?  It might be worth considering.  It depends on the heat transfer coefficient needed.

[jaggu27]

Sir its is an existing vessel and is in the structure. Our people will do the welding work in site itself. Kindly tell me how to calculate no of coils for a given area.

[breizh]

http://www.cheresour...-and-full-coil/
Hi,
Consider this resource available in the forum ( search engine :limpet coil).

Breizh

[latexman]

Calculations are great, but to maximize productivity (cool as fast as possible) the heat transfer area should be maximized where wetted inside the vessel.

 

Also, look at limpet coils on similar sized vessels, I think you will find the size of coils, pitch, spacing, etc. are pretty standard.

Edited by latexman, 21 April 2015 - 07:40 AM.

[curious_cat]

Can you post actual numbers? What is your heat load? Vessel dia? CW temp? Process Temp.? That will constrain your choices. 

 

e.g. Your heat load may be so high that using a circulation loop with a HEX is your only cooling option. 

 

Or the allowable pressure drop might constrain how many turns you can use. Or what lowest half pipe dia. 

[Napo]

Dear Jaggu27,

 

Maybe the attached information help you.

 

Regards,

 

Napo.

Attached Files

•  Coil heat exchanger.pdf   2.53MB   1859 downloads

[jaggu27]

Dear all 

 

I want to cool, the mixture from 40 to 10 degrees celsius. Details are as follows

 

hot side

 

density : 1000 Kg/m³

viscosity: 10 CP

Heat capacity : 1.791 KJ/kg. ^oC

Initial temp : 40^oC

Final temp: 10^oC

 

Vessel

T.L to T.L 2400mm

2:1 ellipsoidal

1800mm ID

 

Agitator

 

115 PM

3.7 KW motor

 

 

Cooling side

Chilled water

initial temp : 5^oC

heat capacity :4.1868KJ/Kg. ^oC

 

For this I got the heat transfer area as 9.3 m2 from the consultant. I need the nusselt number correlation as well as the formulas to find the number of coils required to give the above heat transfer area. Also how to choose the size of limpet coil ? Kindly help

 

Regards

Jagadeesh

[breizh]

Hi ,
For correlation refer to the document attached.

Good luck

Breizh

[curious_cat]

 

 

For this I got the heat transfer area as 9.3 m2 from the consultant. I need the nusselt number correlation as well as the formulas to find the number of coils required to give the above heat transfer area. Also how to choose the size of limpet coil ? Kindly help

 

 

How could the "consultant" calculate the heat transfer area without knowing / assuming coil dimensions? Won't flow rate / velocity on the coil side matter?

 

Or was this an approximate estimate?

[latexman]

I think the time to go from 40^oC to 10^oC is critical too.  Refer to Kern's Process Heat Transfer for the solved differential equations for many batch cooling and heating processes.

[breizh]

Hi ,
In line with Latexman's suggestion ,consider this resource.

[curious_cat]

I think the time to go from 40^oC to 10^oC is critical too.  Refer to Kern's Process Heat Transfer for the solved differential equations for many batch cooling and heating processes.

 

Often, a spreadsheet where you approximate the ODE by piecewise approximations will give you a fairly close answer. 

 

In light of the uncertainity in all the other parameters the error isn't too large.