Learning Forum

[tandinhtamky]

Hi there,

I working for heat generation simulation of 18650 Li-ion batt, natural convection only.

All properties i had. In order to simplify a model, 1 batt cell is a homogeneous solid, with thermal conductivity in axial & radial is different. I am trying to write a udf code for heat generation rate of battery material. But, something were wrong.

To ensure all parameters except heat generation rate value work, I setup a heat generation rate with constant value (instead of udf code) is 10 000. And result show good.

Now, i keep all parameters not change, just setup a heat generation rate is UDF code. It's divergence. And I dont know why it happened !! Please give me a solution. I'm so grateful for that.

Below are some my setup. Thank you so much !!

Mesh: (~300k cells)

[DrAmine]

Hi, can you perhaps first start debugging the functions used in the UDF if the are returning correct values?

for (i=0;i<6;i++)
{
u=u+(c[i]*pow(soc,i)); /* u equal to dE/dT ; mV/K */
}
q=u/1000*I*temp;
R=-1329.9*pow(soc,5)+4183.3*pow(soc,4)-5084.9*pow(soc,3)+2971.2*pow(soc,2)-825.17*pow(soc,1)+141.47;
Also check the return values and also verify if they result in W/m┬│. Probably you need to divide by the whole cell zone volume.
Moreover your expression is not really complicated: why not using Fluent Expressions instead.