NTGK Low heat generation problem

[1929974]

Hi all,

I'm simulating a 1S3P cylindrical 21700 battery module using the MSMD-NTGK model in Fluent 2024 R2, and I’ve encountered a puzzling result regarding heat generation.

What I did:

1. Using SpaceClaim, I created a single 21700 cell with positive and negative tabs.
2. I copied that cell-tab set to build a 1S3P configuration (three parallel cells in one series).
3. Then I created busbars to connect the tabs accordingly.
4. In Fluent, I assigned the NTGK battery model properly, defined the pack as 1S3P, and applied a 3C-rate discharging condition.
5. Each cell is defined as an individual solid zone (cell_1_1s1p, cell_2_1s2p, etc.), and I confirmed that the total current is correctly distributed (14.4 A total, 4.8 Ah × 3 × 3C).

The issue:

- In my previous single-cell 1.5C simulation, the volume average heat generation rate was about 60,000 W/m³.
- But in this 1S3P module 3C simulation, the volume average heat generation rate was about 60,000 W/m³.
- This seems too low, and no increase in heat generation is observed despite increasing the overall current and cell count.

What I already checked:

- The 1S3P connection is correct (battery pack: 1S3P confirmed in console).
- All cells are separate solid zones (not merged).

What I want to understand:

Why is the heat generation lower than that of a single-cell 1.5C discharge, even though both the number of cells and the discharge C-rate have increased?
I would appreciate it if you could point out where I might be making a mistake.

Thanks in advance for any insight or advice!

 

Battery Network Zone Information:

----------------------------------------------------------
Battery 1s1p
Active zone: cell_1_1s1p
Battery 1s2p
Active zone: cell_2_1s2p
Battery 1s3p
Active zone: cell_3_1s3p

Passive zone 0:
bar2
n_tapzone_1
n_tapzone_2
n_tapzone_3
Passive zone 1:
p_tapzone_1
p_tapzone_2
p_tapzone_3
bar1
----------------------------------------------------------

Number of battery series stages = 1; Number of batteries in parallel per series stage = 3
*************END OF BATTERY CONNECTION INFO***********