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Thermal Simulation with hotter and colder temperatures than boundary conditions - suggested Solutions didnt work

Question asked by Andreas Lunzer on Aug 23, 2016
Latest reply on Aug 23, 2016 by Jay Seaglar

I have a question regarding thermal simulation. First of all - I tried to duplicate the study from a steady state study and copy the mash with the same result and already looked for answers. I realized some people have the same problem, but I didn't find a solution

 

I am simulation a cooled metal block, in which a hot object cools down in a hole. I chose the body for the initial temperature from the tree menu and for the constant temperature i chose the surface of the "cooling tunnel" an set it to 21°C.

 

My hot part was set to initial 200°C

The metal part was set to initial 25°C

and the cooling tunnel so a constant temperature of 21°C

 

I let it cool for 8 sec and experienced at the beginning weird results. Ranging from negative temperatures to higher temperatures than 200°C.


So i simplified it an those mistakes occur on the touching surfaces of 2 blocks. One block is 25°C and the other one is 200°C at the beginning.

 

 

as a result i get a not as dramatic but similar result of non logical temperatures.

Simplified Heat Problem.PNG

if i increase the time-step my coolest temperature drops under 20°C.

 

I reduced the mesh size and time steps with no success.

 

I guess the problem in my more complex part is similar to this one

 

I appreciate any help and ideas!


Greetings

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