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Thermal transient study positive heat flux leads to temperature drops?

Question asked by Vincent Dai on Jul 3, 2018
Latest reply on Jul 3, 2018 by Vincent Dai

So I am using a Solidworks simulation to simulate a energy beam colliding with a heat dump, and I am using heat flux to act as the energy transfer the beam is leaving on the beam dump. For some reason using heat flux with a transient study on the surface of the beam dump causes the temperature in certain areas to fall beneath the initial temperature of 300K, which does not seem to make thermodynamic sense to me.


I already checked that I selected the whole bodies and not just the faces; when I run without any heat flux the whole assembly is consistently 300K. It is only when I add in some heat flux that some areas fall beneath 300K. There are no other thermal loads on my model besides the heat flux and the initial temperature, so I do not understand why the temperature would fall beneath 300K. I also checked with a steady state study, and in that the model did not fall beneath 300K at any point.


In the image that I attached, you can see that the thermal component on the side goes down to 299.2K; near the top left there is a sensor that says Model Min and records 299.245K @ 0.01s. With the laws of thermodynamics I fail to see how the temperature could drop even this small amount.Dump Problem.png


Any advice is greatly appreciated, this problem has been completely baffling me.