Cold Pipe

avp081090 · Post by **avp081090** » Mon Apr 28, 2014 2:25 am -1100

Greetings

It is possible to model condensation on a cold pipe wrapped in a insulating material? My biggest issue is the circular geometry - can this be made?

Best regards.

Christian Bludau · Post by **Christian Bludau** » Tue Apr 29, 2014 3:12 am -1100

Hi,
for that you can use the calculation with radial geometry. Go to the computational parameters, enhanced. Scroll down the list with the control parameters. Here you will find the "Radial Diameter". This diameter is the distance from the left side of you construction to the rotation axis which is left of your construction.
So if you set it to zero, that will be the rotation around the left side of you construction.
I attach you a pic for better understanding.
Christian

Please note:
R = 0m is only working with WUFI Pro. For WUFI 2D R has to be larger than 0 (R > 0). For no radius please use something like R = 1e-6 m .

fostertom · Post by **fostertom** » Tue Apr 29, 2014 11:38 pm -1100

Cool!

avp081090 · Post by **avp081090** » Wed Apr 30, 2014 2:37 am -1100

Christian Bludau wrote:Hi,
for that you can use the calculation with radial geometry. Go to the computational parameters, enhanced. Scroll down the list with the control parameters. Here you will find the "Radial Diameter". This diameter is the distance from the left side of you construction to the rotation axis which is left of your construction.
So if you set it to zero, that will be the rotation around the left side of you construction.
I attach you a pic for better understanding.
Christian

Thanks - So should I model a cold pipe as shown in the the attached pic.? what about the height/length of the tube? and boundary conditions?

Best regards

veitner · Post by **veitner** » Wed Apr 30, 2014 3:02 am -1100

In this case I would suggest at top and bottom adiabatic and whatever you want left and right - so this special case would be also possible in WUFI1D

Christian Bludau · Post by **Christian Bludau** » Wed Apr 30, 2014 3:11 am -1100

I think the hight of the section does not have to be very high. I would try something like half a meter. The radial diameter is the inner diameter, thats right. As veitner wrote: set inside the inside climate and out side the surrounding climate. Keep in mind that radiation/rain would be a problem, as there is no certain orientation. Upper and lower end set as adiabatic. If you want to model the dew water forming on the surface of the tube, you have to add a layer which can store the dew water (eg. 1-5mm mineral wool), as at the surface itself there can be no dew water in WUFI.

avp081090 · Post by **avp081090** » Wed Apr 30, 2014 3:26 am -1100

veitner wrote:In this case I would suggest at top and bottom adiabatic and whatever you want left and right - so this special case would be also possible in WUFI1D

Okay så maybe i just need to model it as the rectangle shown in my picture without adding a radial diameter?

Best regards

veitner · Post by **veitner** » Wed Apr 30, 2014 5:55 am -1100

No - add the radial diameter. Supplying this parameter WUFI switches to cylindrical coordinates (https://wufi.de/literatur/K%C3%BCnzel%2 ... nsport.pdf, page 40).

Lafont Antoine · Post by **Lafont Antoine** » Tue Dec 06, 2016 11:15 pm -1100

avp081090 wrote:Greetings

It is possible to model condensation on a cold pipe wrapped in a insulating material? My biggest issue is the circular geometry - can this be made?

Best regards.

Dear Wufi team,

I have to work on quite the same topic. My aim is to evaluate the mass condensation product on a simple steel pipe. The pipe is cold inside (around 8°C) but it crosses a boiler room.
I use cylinder geometry and put very high Sd-values between exterior and interior surface so that the material pretends to be steel.

Can we consider the "total water content" (kg/m2) as the mass condensation product?

Many thanks,

Regards,

Antoine

Christian Bludau · Post by **Christian Bludau** » Thu Dec 08, 2016 4:09 am -1100

Usually you can that.
Unfortunately you did not post the information about the construction you are looking at or the layers you are simulating. Please describe your construction.

Lafont Antoine · Post by **Lafont Antoine** » Thu Dec 08, 2016 4:43 am -1100

Dear Wufi team,

thank you very much for your quick answer. Much appreciate!

I'll to be a bit more precise with a small scheme.

To sum up:
- a steel pipe crosses a warm ambiance (around 25°C and let's assume 50% HR).
- liquid inside the pipe is 8°C.
- according to psychrometrics curves, there will be condensation on the pipe if surface temperature goes under 14°C.

My question is:
Could we assess mass of condensation products on the pipe throughout a year?

Thanks a lot!

Best regards,

Antoine

Christian Bludau · Post by **Christian Bludau** » Thu Dec 08, 2016 4:51 am -1100

Ah, now I can see the problem. WUFI can not calculate condensate on the surfaces. For doing that you have to add a thin layer, which can store the water, e.g. mineral wool with the thermal conductivity of air.

Christian

Lafont Antoine · Post by **Lafont Antoine** » Thu Dec 08, 2016 5:16 am -1100

Dear Christian,

Thanks a lot for your advices. In that case, what is the thikness you would advice for your "virtual mineral whool layer"?

Regards,

Antoine

Christian Bludau · Post by **Christian Bludau** » Thu Dec 08, 2016 8:34 pm -1100

That depends on the amount of water. maybe something between 1 mm and 1 cm. If the layer is to thin, dew water will saturate it to fast and will not get an realistic amount.

Christian

Alberto Morales · Post by **Alberto Morales** » Thu May 26, 2022 1:07 am -1100

hi,

Could you update this link https://wufi.de/literatur/K%C3%BCnzel%2 ... nsport.pdf please? it does not work anymore

Could you repeat plase the concept of Radial Diameter using a real example/image? it is not very clear in your previous feedback, apologise

Thanks in advance

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