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# calculate the Internal area of a tube in an evaporizer

## calculate the Internal area of a tube in an evaporizer

(OP)
[b]Dear friends,
I am trying to calculate the Internal area of a tube in an evaporizer. I am using the formula (pi*D^2)/4, How to I determine the D? I understand that's the diameter of the tube.

### RE: calculate the Internal area of a tube in an evaporizer

That's the cross sectional area, the inside surface area is based on the cross sectional area and length.

Is it an existing unit that you are inspecting? D would be based on on the tube outside diameter and the wall thickness...

### RE: calculate the Internal area of a tube in an evaporizer

In most evap application the tube walls are thin enough (compared to diameter) that people use use pi*D*L and ignore that the ID surface is slightly smaller.
If your walls are heavier and you want to correct the use pi*(D-2w)*L Where w is the nominal (ordered) wall thickness. The actual walls will be slightly less than this but you have no way of knowing the actual wall thickness.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

### RE: calculate the Internal area of a tube in an evaporizer

Don't you have a fabrication drawing or the old spec? If so, the do, di, and L should be on there, or it will define the nominal size and standard you need to refer to.

Good Luck,
Latexman

### RE: calculate the Internal area of a tube in an evaporizer

(OP)
I am actually designing the evaporizer of a Process Plant that produces acetone.

A = N. Π. Do. L

### RE: calculate the Internal area of a tube in an evaporizer

(OP)
@GEOGERVERGHESE,
What is N, Do, L. How do i find out the Do(assuming thats the outside diameter????

### RE: calculate the Internal area of a tube in an evaporizer

N = Number of tubes
Do = od of tube - you will find this on the TEMA datasheet for the vaporiser
L = length per tube

Most heat exchanger TEMA datasheets would state explicitly the total heat exchange surface area also

### RE: calculate the Internal area of a tube in an evaporizer

#### Quote (Vivaldi SMITH)

How do i find out the Do(assuming thats the outside diameter????

The designer (you) has to decide what size tubes to use.

Too small and they may plug up easily. Too large and your heat transfer may be low. Any past experience from similar operations to guide you?

Good Luck,
Latexman

### RE: calculate the Internal area of a tube in an evaporizer

You need to estimate the heat load, efficiency, HT coef, and then you can arrive at a total surface area.
People use the sizes that they do because of the tradeoffs with thermal eff, hydraulic eff, and fabrication costs.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

### RE: calculate the Internal area of a tube in an evaporizer

WOW ......

MJCronin
Sr. Process Engineer

### RE: calculate the Internal area of a tube in an evaporizer

@vivaldi, Your line of queries tells me you have a long way to go before you can confidently do a thermal design for a vaporiser. Dig up your heat transfer textbook that is obviously collecting dust and start at page 1. A practicing engineer's heat transfer textbook that you must have is "Process Heat Transfer" by DQ Kern. Do not attempt any computer thermal simulations until you have read through these books and done most of the questions at the end of each chapter. Also get a copy of the TEMA book for heat exchangers.

### RE: calculate the Internal area of a tube in an evaporizer

Looking at OPs history, it is likely this is a student question...

### RE: calculate the Internal area of a tube in an evaporizer

Perhaps an 8th Grader or High School Student .....

MJCronin
Sr. Process Engineer

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