Learning Forum

[mobleysn]

Project is a temperature-over-time simulation of a battery pack with user-defined heat generation from the batteries.

Whenever I run the simulation, it runs as I would expect (batteries heating up slowly and the pack around it heating up slower) for about 40 seconds (8 time steps, 5s each) and then it begins displaying an odd message in the TUI: "temperature limited to 1.0000e00 in __ cells in zone __." The cells and zones change as the simulation continues. The scaled residuals graph begins well, with vertical zig-zags that I am accustomed to seeing, but then abruptly becomes a constant upward slope until it hits 1e0, where it levels off. 

The temperature display is very odd as well. The expected values are somewhere around 60C max and 40C minimum, but the contour instead shows very unrealistic results with a max of 1200C and a min of -1500C. 

The simulation has this issue whether using a user-defined function for heat generation or using a constant, so I don't think the heat generation is causing this problem.

I would like advice on where I am possibly doing something wrong to cause this issue, please!

[Konstantin]

1) can you tell us more about this case: dimension of the pack, boundary conditions (specifically thermal conditions), source strength (assuming constant-value source), source location (is it restricted to a region inside the battery or applied to the entire volume).

2) tie up temperature limits to be closer to what you expect, but still leave some leeway for the temperature to fluctuate during the iterative process (on the order of 50 to 100 K)

 

[mobleysn]

The pack is about 130mm by 45mm. The pack is a phase-change material, I have it listed as a fluid in the simulation for melting purposes. There is a convection coefficient on external surfaces of 5 W/m^2-K. The initial temperature of the system is 22°C, with a heat generation coming from the entire volume of the batteries (in "cell zone conditions" I have the entire battery selected as the source). The batteries are aluminum (from the engineering source in ANSYS) but with cylindrical orthotropic thermal conductivity instead of the constant conductivity that it defaults to. 

The source strength I have been using is a user defined function, but I have also tried a constant of 2500 W/m^3 as a test to see if the UDF was the issue (it was not). I am not sure if 2500 is reasonable, honestly, since I don't have much knowledge about battery heat generation. 

How do I set temperature limits? I know approximately what range I need, but I don't know how to set that up in the software. 

[DrAmine]

Only solid zones? Can you list the zones and the materials used.

[Konstantin]

try with constant conductivity to confirm it runs fine. This will make the ortho conductivity the main suspect. Hint for setting the solution limits: read Fluent User Guide.

[mobleysn]

Well, I'm not sure what exactly was the issue in this specific simulation, but I made a new one from scratch and for some reason this time around it worked fine. However, now I am having issues with initialization. Should I make a new thread for that issue?

[Konstantin]

please start a new thread to have discussions focused on a specific topic, and we'll reply you there

[Battery]

I did have similar issues in the past, I'm curious what causes this.