PDE tool box, internal heat generation and BC conditions

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Dear all,
I am currently using the PDE tool box to model the thermal behavior of a cylindrical lithium-ion battery (2D,x-y). The main experiment consists on cycling a battery inside a climatic chamber. The cell has a heat generation which is used as InternalHeatSource (Joule heat [W]) and the heat exchange with the climatic chamber is only done by convection.
After running the model, I got some weird results which I suspect are due to the internal heat generation or boundary conditions functions. As a result, I would like to know if the following settings are correct:
  • Thermal prorperties : Thermal conductivities given as c=[kx ; ky] [W/ m.K], Density [W/m^3], specific heat capacity [J/ kg.K], geometry in [m]
  • Boundary conditions : Convection coefficient h [W/m^2], (equal to 10(natural convection) in my case) and Ambient Temperture [°C]
thermalBC(Thermal,'Edge',[1 2 3 4], 'ConvectionCoefficient',10,'AmbientTemperature',25)
  • Internal heat generation: The value (heatSourceValue) is given to internalHeatSource in [W/m^3]
HeatSource= @(region,state) heatSourceFun(region,state,IntHeat);
function heatSourceValue = heatSourceFun(region,state,IntHeat)
Volume_cell= (0.07)*pi*(0.0105)^2; % Battery volume in m^3
if isnan(state.time)
heatSourceValue= NaN(size(region.y));
elseif state.time==0
heat=abs(IntHeat(1,2)- (mean(state.u)+273.15)*IntHeat(1,3));
heatSourceValue= (heat/Volume_cell)*ones(size(region.y));
elseif state.time<= max(IntHeat(:,1))
heat=abs(IntHeat(floor(state.time),2)-(mean(state.u)+273.15)*IntHeat(floor(state.time),3));% floor = arrondir
heatSourceValue= (heat/Volume_cell)*ones(size(region.y));
else
heatSourceValue= zeros(size(region.y));
end
When I look at the results, the temperature estimations given by the model are considerably higher than the results measured by the surface-mounted thermocouples.
Thanks in advance,
Juan.
  2 Comments
Ravi Kumar
Ravi Kumar on 22 May 2019
Hi Juan,
Is your model axisymmetric. You say "cylindrical lithium-ion battery (2D,x-y)", what does this mean? If its axisymmetric, then you need some additional modificaiton to formulaiton of the probelm to solve.
Regards,
Ravi
juan ugalde
juan ugalde on 22 May 2019
Hi Ravi,
The model geometry is indeed axisymettric. The cylinder is approched as a 2D surface.
Thanks
Juan

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Answers (1)

Ravi Kumar
Ravi Kumar on 22 May 2019
If the problem is axisymmetric, then you need follow the approach similar to this example:
Note that you have to account for the axisymmetric modification in all your operations, like postprocessing, all of which might not be covered in the example. Let me know if you get you temperature distribution matches expectaion using the axisymmetric approach.
Regards,
Ravi
  4 Comments
juan ugalde
juan ugalde on 24 May 2019
Dear Ravi,
I tried to add the attachements to this message but it didn't work. Can I send them to you in private?
Thanks again,
Juan.
tar abu
tar abu on 20 Jun 2020
Dear Juan Ugalde,
hey do you still have the attachements? if so please send them to me .
Thank you,
Tar.

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