Insulation calculation to prevent condensation 2

[ivoryhorseman]

Hello people

I need to calculate the thickness of insulation required for a cylinder of inner radius 20cm. The temperature inside the cylinder is -165°C and
outside temperature being 25°C.

similarly how does it vary for a wall of thickness 50cm.

Do i need to provide any more information or is this sufficient.

the insulation coating is intended to prevent condensation.
can somebody provide the formulae for the calculation.

thanks in advance .............

 

[IRstuff]

What's the dewpoint of the air?

The air temp minus the dew point minus some margin is what the allowable convective temperature drop is. Use the convection equation to determine how much heat is allowed to flow inward. The allowable heat flow divided by surface temp minus the interior temp divided by thermal conductivity will get you to the required thickness.

TTFN
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[willard3]

You can find this in ASHRAE volumes.

 

[ivoryhorseman]

Willard3 can you please provide a link

 

[willard3]

You have to own ASHRAE volumes or know somebody who does or be a member and subscribe to the publixcations.

Your best bet here may be to consult an Engineer who does HVAC.

 

[sspeare]

ivoryhorseman: possible typo in your post? If the radius is 20 cm, then diameter = 40 cm, or 15.7 inches. But you said the wall thickness was 50 cm (= 19.6 inches ?) I'm lost. Anyway, just to get you "in the ballpark", you might try a few possibilities out at the attached site. Also, as others have said, you should study how to do the heat transfer calc by hand, so you really learn how the numbers work. Good luck!

 

[MintJulep]

And it sort of matters if the insulation is vapor permeable or not.

 

[ivoryhorseman]

Thank you.