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© 2011 ANSYS, Inc. June 26, 2014 1

Thermal Transient Simulation with ANSYS Software – Case Studies

Sandeep Sovani, Ph.D.

Manager, Global Automotive Strategy

ANSYS Inc, Ann Arbor, MI, USA

Xiao Hu, Ph.D.

Principal Engineer

ANSYS Inc, Ann Arbor, MI, USA

© 2011 ANSYS, Inc. June 26, 2014 2

New Paradigm 1 – Multidomain Simulation

Phenomena at one level affect those at other levels and need to be simulated in simultaneous co-simulation

Electrode Level

•Electrode layout •Manufacturing process development •Life

Molecular Level

•Material innovation •Material selection

Cell Level •Charging, dischar-ging profiles •Heating •Safety under abuse •Swelling, deformation

Pack Level •Thermal Mgmt •BMS Logic •Safety •Durability •NVH •EMI/EMC

Powertrain and Vehicle Level

•System Integration

Smal

l Sca

le

Larg

e S

cale

© 2011 ANSYS, Inc. June 26, 2014 3

A Total Li-Ion Battery Simulation Solution

© 2011 ANSYS, Inc. June 26, 2014 4

Newman’s 1D Electrochemistry Model Electrode Level

Manufacture Material selection Electrochemistry

Starting from the electrode level . . .

3D Electrochemistry Simulation

Multidomain Simulation

© 2011 ANSYS, Inc. June 26, 2014 5

Multidomain Simulation – Electrode Level

Li concentration in electrodes during discharge

ANSYS Case Study – 3D Electrochemistry Modeling

© 2011 ANSYS, Inc. June 26, 2014 6

ANSYS Simplorer’s Results

x=0

x=Lp+Ls+

Ln

x=Lp+Ls

x=Lp

1/10 C

1/2 C

1 C

2 C

4 C

6 C

8 C

10 C

White et al’s Results

Multidomain Simulation – Electrode Level

ANSYS Case Study – Pseudo 2D Electrochemistry Newman Model – Quantitative Validation

Long Cai, Ralph E. White, Journal of Electrochem. Soc., 156 (3), A154-A161 (2009)

Xiao Hu, Shaohua Lin, and Scott Stanton, SAE 2012-01-0665

© 2011 ANSYS, Inc. June 26, 2014 7

ANSYS Simplorer’s Results White et al’s Results

Multidomain Simulation – Electrode Level ANSYS Case Study – Pseudo 2D Electrochemistry Newman Model – Quantitative Validation

Long Cai, Ralph E. White, Journal of Electrochem. Soc., 156 (3), A154-A161 (2009)

Xiao Hu, Shaohua Lin, and Scott Stanton, SAE 2012-01-0665

© 2011 ANSYS, Inc. June 26, 2014 8

Newman P2D Electrochemistry Model in Fluent (CAEBAT project)

0 Li

s j

r

cr

rr

D

t

c sss 2

2

0ln Li

eDe jckk

Li

eeee j

F

tcD

t

c

1)(

RT

F

RT

Fij ca

a

Li expexp0

Domains

• negative electrode

• separator

• positive electrode

• spherical particles

A system of DAEs are solved for every CFD cells:

- Total number of equations: (n_Cs+2) *n_NE + 2n_SP+(N_Cs+2) n_PE

- Memory requirements: N_cell*{(n_Cs+1) *n_NE+ n_SP +(N_Cs+1) n_PE)}

L. Cai and R.E. White, “Reduction of Model Order Based on Proper Orthogonal Decomposition for

Lithium-Ion Battery Simulations” J. of Electrochemical. Soc. 156(3) A154-A161 (2009).

© 2011 ANSYS, Inc. June 26, 2014 9

Temperature Results Based on Electrochemistry

-110

-90

-70

-50

-30

-10

10

30

50

0 200 400 600 800 1000 1200 1400

Cu

rre

nt

(A)

Time (s)

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. . . incorporating electrode level effects into the cell level . . .

Cell Thermal Model with Electrochemistry Cell Level Electrical Model Heat Generation Abuse Nail Penetration Crush

Multidomain Simulation

© 2011 ANSYS, Inc. June 26, 2014 11

Cell Level – Equivalent Circuit Model (ECM)

Battery Equivalent Circuit Model (ECM)

Simulation Testing

X. Hu, L. Collins, S. Stanton, S. Jiang, "A Model Parameter Identification Method for Battery Applications", SAE 2013-

01-1529.

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• 28 cells are connected in a module

• 4 modules are connected to the final configuration

Module/Pack Level – ECM

X. Hu, L. Collins, S. Stanton, S. Jiang, "A Model Parameter Identification Method for Battery Applications", SAE 2013-

01-1529.

Battery Pack ECM

Simulation Results

© 2011 ANSYS, Inc. June 26, 2014 13 X. Hu, L. Collins, S. Stanton, S. Jiang, "A Model Parameter Identification Method for Battery Applications", SAE 2013-

01-1529.

Cell Level – ECM Extraction Tool

ECM Extraction Toolkit

ECM Model Workflow

© 2011 ANSYS, Inc. June 26, 2014 14

Module Level – CFD Thermal

Temperature Distribution

Temperature and Pathlines Temperature Distribution

Temperature Distribution

© 2011 ANSYS, Inc. June 26, 2014 15

Battery Thermal Behavior via ROM

Type 1: Thermal Network

• Careful calculation and calibration needed

• Accuracy compromises

Type 2: LTI – state space

• Can be as accurate as CFD

• No calibration

LTI t t Step

Input

Step

Respons

e

1

© 2011 ANSYS, Inc. June 26, 2014 16

1. Create the CFD model

2. Generate step responses Icepak has specialized tools

Other CFD codes are fine

4. Simulate inside Simplorer

3. Extract LTI ROM Use Simplorer

LTI ROM for Battery Cooling ANSYS CFD

© 2011 ANSYS, Inc. June 26, 2014 17

LTI ROM gives the same results as CFD.

LTI ROM runs in less than 2 seconds while

the CFD runs 2 hours on one single CPU.

X. Hu, S. Lin, S. Stanton, W. Lian, “A Foster Network Thermal Model for HEV/EV Battery Modeling,” IEEE

TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 47, NO. 4, JULY/AUGUST 2011

X. Hu, S. Lin, S. Stanton, W. Lian, “A State Space Thermal Model for HEV/EV Battery Modeling", SAE 2011-01-1364

Heat Profile

LTI ROM for GM Battery Module

© 2011 ANSYS, Inc. June 26, 2014 18

Module Level – ROM for Thermal

ROM vs CFD ROM for the Battery Module

© 2011 ANSYS, Inc. June 26, 2014 19

SVD+LTI technology allows for quick temperature distribution calculation in addition to average temperature calculation.

Using a heat source from GM, SVD+LTI ROM is applied to the GM 16 cell case.

SVD+LTI ROM : GM 16 Cell Test Case

Heat source used

© 2011 ANSYS, Inc. June 26, 2014 20

1. Create the Fluent CFD model

2. Generate step responses

3. Extract SVD+LTI ROM • Use Simplorer

4. Simulate inside Simplorer

SVD+LTI ROM for Battery Cooling

ANSYS CFD

© 2011 ANSYS, Inc. June 26, 2014 21

SVD+LTI ROM Validation: GM 16 Cell Test Case

CFD (200 sec)

SVD+LTI ROM (200 sec)

CFD (400 sec) CFD (600 sec) CFD (800 sec)

SVD+LTI ROM (400 sec)

SVD+LTI ROM (600 sec)

SVD+LTI ROM (800 sec)

© 2011 ANSYS, Inc. June 26, 2014 22

SVD+LTI ROM Statistics for GM 16 Cell Test Case

CFD mesh size 3,025,067

Number of steps in step response run 180

Size of matrix A 3,025,067×180

Number of snap shots used for SVD calculation 180

SVD calculation time 4 min 50 sec

SVD calculation memory usage 8.1 G

SVD+LTI ROM extraction time 5 min

CFD validation simulation time on single CPU 5 hr

SVD+LTI ROM simulation time on the same

single CPU

a few seconds

© 2011 ANSYS, Inc. June 26, 2014 23

SVD+LTI ROM Validation

CFD (10 sec)

SVD+LTI ROM (10 sec)

CFD (20 sec) CFD (30 sec) CFD (40 sec)

SVD+LTI ROM (20 sec)

SVD+LTI ROM (30 sec)

SVD+LTI ROM (40 sec)

© 2011 ANSYS, Inc. June 26, 2014 24

SVD+LTI ROM Statistics for the Test Case

CFD mesh size 12,209,486

Number of steps in step response run 120

Size of matrix A 12,209,486×120

Number of snap shots used for SVD calculation 60

SVD calculation time 3 min

SVD calculation memory usage 18 G

SVD+LTI ROM extraction time 5 min

CFD validation simulation time on six CPUs 20 hr

SVD+LTI ROM simulation time single CPU a few seconds

© 2011 ANSYS, Inc. June 26, 2014 25

ECM calculates heat source and sends it to the two ROMs.

LTI ROM calculates average temperature and sends it to ECM.

SVD+LTI ROM calculates temperature distribution.

GM Battery Module – ECM Coupled with ROMs

© 2011 ANSYS, Inc. June 26, 2014 26

ROM Results

LTI ROM calculates average temperature.

SVD+LTI ROM calculates temperature field.

Average Temperature Heat Source for One Cell

© 2011 ANSYS, Inc. June 26, 2014 27

Module/Pack Level – Bus Bar Model

Electromagnetic FEA Analysis for Busbar RLC Network Extraction

© 2011 ANSYS, Inc. June 26, 2014 28

Full Battery Simulation

Voc = -1.031*exp(-35*(abs(IBatt.V/Vinit))) + 3.685 +

0.2156*(abs(IBatt.V/Vinit)) - 0.1178*(abs(IBatt.V/Vinit))^2 +

0.3201*(abs(IBatt.V/Vinit))^3 +

0.3/30.0*(U1.Temp_block_1-273)

© 2011 ANSYS, Inc. June 26, 2014 29

Full Battery Simulation

© 2011 ANSYS, Inc. June 26, 2014 30

Conclusions

Battery is a multi-scale multi-physics application.

ANSYS provides tools for all aspects of battery simulation.

Furthermore, ANSYS integrates different models into battery system level simulation through model order reduction.

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