Amount of N2 needed to reduce the dew point of a piping system.

[Hruine123]

Hi Everyone,
I need some help regarding using nitrogen to reduce the dew point of a piping system.
How would you calculate the amount of N2 gas needed to reduce the dew point of a 30m3 piping system to -25c?

I assume i would need to use the Q=m*CP*dT formula but not sure whether to use ambient temp or dew point temp for the dT.
Thanks in advance.

 

[csk62]

If you need to dry out a system to a specified dew point it is much easier to flow warm dry N2 gas through it than simply put a specified amount of gas in a closed volume.

 

[LittleInch]

So is this:

An existing pressurised gas with an dewpoint of ??
A system open to atmosphere that you want ot condition to -25
Something that has liquid inside that you want to condition?
Or something else?

Q is flow rate and that's a heat flow equation.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

This gets complicated. What is the temp and humidity to start with? What is the surface?
The big problem is absorbed moisture on the walls, this is why it has been suggested to flow warm dry nitrogen.
Shape matters also, if this is a long run of 2" with no branches then it should be straight forward.
The more complex the piping the harder the job.
You are likely talking about flowing warm nitrogen at a good flow rate for many hours in order to get that dry.
Is there any free water in the pipe? If so you might want to think about first flushing with a solvent (alcohol?).

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P.E. Metallurgy

 

[Iomcube]

Hruine123, you will require psychometric charts to accurately determine dewpoints. However if you provide further info for instance chemical composition of the fluid inside the pipe you can then use DWSIM opensource simulator to 'adjust' feed N2 flow to acquire desired dewpoint