Internal Heating Coil Design

[takiyasamsama]

Hi,

We are going to design a vessel with a coil and I am not very familiar to design of heating / cooling coil. How may I find a reference to design of heating or cooling coil. Our problem now is that we need to find the height of the coil and to determine the length of the coil as well.

 

[pv_mkk]

you need

-flow rate to obtain diameter of coil
-internal pressure/temp and material to obtain thickness of coil
-surface area for obtain length and height

 

[takiyasamsama]

How about the height? How do we determine the height? Is there any formula to determine the height? Specifically starting center to end center.

from a book I refered to states that the pitch between the two diameter equals to 1.5*outside diameter, and the outside diameter spacing equals to 0.5*outside diameter.

So based on those two formulas, let say I have 7 no. of turns, so it would be:
(1.5*outside diameter)*6 + (0.5*outside diameter)*6

is this calculation valid to determine the height of the coil?

 

[georgeverghese]

And also calculate overall U for the coil based on calculated value for hi and ho - it might help to go through that heat transfer text book that is collecting dust on the shelf!
There is simply too much to tell to be of much use at the moment - you can come back to this forum when you have gone through chapters on forced and natural convection.
Pressure drop can influence the design of this coil also.

 

[takiyasamsama]

Can someone verify that to find the starting-center to end-center height equals to pitch multiply by the number of turns of the coil.

 

[georgeverghese]

Get the impression this is a vertical helical coil with natural convection on the outside - can't find correlations for ho specific to this configuration for external natural convection in DQ Kern or Perry. In my opinion, we could approximate this as unimpeded natural convection up along a vertical plate, for which correlations are easily found. You could run a check / comparison calc with this approximation also to get some confidence in the value for ho.
For internal hi, there are correlations available in Perry for coils.
Most likely, ho will control the value for U if this is clean service inside and outside.