Learning Forum

[MToTheE]

Hello Community,

my goal is to look how a block of wood reacts, when it cools down. My setting  is quite simple. I have a cubic block of wood which is isolated all around with EPS. At the top the block gets cooled down from 20 to -160 C°. As solution I just want the temperature distribution. The complete bottom of the modell has a steady temperature of 20°C. Also the upper layer of the EPS. 

So the highest temperature in the System is 20°C and the lowest -160° but the max. and min. temperature shown in the solution is +72°C and -340°C. Do anyone know, how that can happen and how I maybe should change the model to get the solution fixed? Actually the grafic output looks logical and right but there are still this way to high and low temperatures. 

 

[MToTheE]

Please let me know which files you need from me to answear the question. Thanks for your help!

[peteroznewman]

What is EPS?

[MToTheE]

Oh excuse me, its a german shortcut. I thought its international. Its styrofoam.

[peteroznewman]

ANSYS Staff are not permitted to open attachments. Please use the Insert Image button to put images into your post.

Did you run a Steady State Thermal model and get the same result?

Here I see you have a Heat Flow in the model. What is that doing?

[MToTheE]

The heatflow is actually unnessecary. I deleted it and nothing changed. It was a perfect insulation at the outer surfaces. So I did the steady state thermal analysis and there are different results, but still confusing ones. The hightest temperature is now 60C° and the lowest -220C°. 

 

Unfortunately it is not possible for me to attache pictures, because there occures an error also on different devices. Thanks for your help!

 

[peteroznewman]

The website is broken today and no one can attach images.

If you make the element size half of the current size, do the results improve?  If you are not on a Student license with node/element limits, you can cut the element size in half again. Plot out how the maximum and minimum values change as a function of element size.

[MToTheE]

I did a parametric study and it didnt solve the problem completely. The maximum temperature gets near the implemented one, but the minimum temperature stays at -200C°.

So now I also can send the pictures of the setup.

At first the perfectly isolated outside.

 

The Temperatue at the top of the wooden block sinking over time until -160C°.

The isolation which stays at 20C° because of the overall environmental temperature.

And at last the visualization of my first test.

[Whiteney1991]

Hi,nI am cooling down the cylindrical part initially at 168 oC using the coolant in the coiled parts at 25 oC. Why could the maximum temperature in results exceed the maximum input temperature of 168 oC yet I am cooling it down? The anticipated average temperature seems okay but the max and min temperatures exceed the expectations in some instances.n

[YasserSelima]

How many elements you have in this cylindrical part. Specifically, how many elements in the radial direction?n

[Whiteney1991]

I have 4828 nodes and 2353 elements.n

[YasserSelima]

in the radial direction? please show a sketchn

[Whiteney1991]

please see what I have attached. I am not sure whether the attachment shows what you require. If it does not, kindly explain to me how I can obtain that. nn

[YasserSelima]

Yes, the attachment shows what I need. Of course you know that temperature distribution in conduction heat transfer is a logarithmic relation. Can you plot an accurate logarithmic relation with two points? This is what you are asking fluent to do. You have two cells in your flange and you are expecting that fluent will estimate the right temperature distribution.nIncrease the number of cell ... probably you need 4-5 times this number of cells.n