air cooling technology for power electronic thermal control · air cooling technology for power...

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Air Cooling Technology for Power Electronics Thermal Management

P.I.: Jason A. Lustbader National Renewable Energy Laboratory May 15, 2012

Project ID #: APE019

This presentation does not contain any proprietary, confidential, or otherwise restricted information.

2

“ Everything on a vehicle

is air cooled…

3


is air cooled…

ultimately ”

4


is air cooled…

ultimately ”

Goal: Develop air-cooled thermal management system solutions that help meet DOE’s 2015 technical targets by 2014

5

Challenges and Barriers − Relevance • In current designs, heat is transferred from the source through a heat

exchanger to a liquid, which is pumped to a remote location, and then the heat is rejected to air through another heat exchanger

• Air cooling has the potential to improve thermal management system cost, weight, volume, and reliability, helping to meet Advanced Power Electronics and Electric Motors (APEEM) technical targets

• Air is a poor heat-transfer fluid – low specific heat – low density – low conductivity

• Parasitic power • Perception and novelty

The Challenge • Everything on a vehicle is ultimately air-

cooled

• Rejecting heat to air can eliminate intermediate liquid loops

• Air is benign and need not be carried

• Air is a dielectric and can contact the chip directly

Advantages

6

It Can Be Done….When?….How?

Photograph references: Left 1st row [1], Left 2nd row [2], Right 1st row [3], Right 2nd row [4]

Honda Insight Power Rating 12 to 14 kW

AC Propulsion AC-150 Power Rating 150 kW

7

Overview

Phase II start date: FY10 Project end date: FY14 Phase II complete: 50%

• Cost – Eliminate need for secondary liquid coolant loop and associated cost and complexity

• Weight – Reduce unnecessary coolant, coolant lines, pump and heat exchangers for lower system-level weight

• Performance – Maintain temperatures in acceptable range while reducing complexity and system-level parasitic losses

Vehicle Technologies Program 2015 Targets 12 kW/l, 12 kW/kg, $5/kW

Total Project Funding: DOE Share: $1,650K

Funding Received in FY11: $700K

Funding for FY12: $550 K

Timeline

Budget

Barriers

• Oak Ridge National Laboratory (ORNL) – Madhu Chinthavali

• GE, Momentive Performance Materials, and Sapa

Partners

8

FY12 Plan – Relevance 2011

Oct

Nov

Dec

2012

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Develop device- level test bench

Design and build system- level test bench

Go/ No-Go

2

Go/ No-Go Decision Points: 1. Use modeling to determine feasibility of design, use device-level testing to validate models and use in conjunction

with models to determine promising cooling approaches 2. Confirm module-level improvement over baseline and that inverter is on track to meet targets 3. Use module-level data and fan testing results to confirm adequate system performance for FY13

Demonstrate module-level

thermal performance

Go/ No-Go

1 Device and module-level modeling, validation, and feasibility analysis

Fan and ducting testing

Module testing attachment design and build

Thermal module prototype build and test

Prototype design Go/

No-Go 3

Device-level testing

Module and system level modeling

Advanced device testing Update electrical design based on thermal management results

ORNL Supporting Tasks NREL Tasks

9

Milestones Date Milestone or Go/No-Go Decision

05/11 Go/No-Go 0: Using NREL’s system-level analysis method, found that it may

be possible to approach liquid-cooling power density using advanced technology for air cooling

09/11 Synthetic and steady jet study showed a 30% improvement in heat transfer with synthetic jets

12/11 Completed device-level test bench

02/12 Baseline device-level testing

02/12 Model validated

03/12 Go/ No-Go 1, Initial design feasibility: Use modeling to determine feasibility of design, validate with device-level testing

04/12 Complete system-level test bench and begin fan and ducting experiments

06/12 Go/ No-Go 2, Module prototype design review: Confirm system-level improvement over baseline and that system will meet targets

09/12 Go/No-Go 3, Module level demonstration: Use module-level data and fan testing results to confirm adequate system performance for FY13

10

Approach

11

Approach

Photograph references from left to right: 1. Top [1], Right [2]; 2. Bottom [3]; 3. [4], 4. [5]

FY10 – Fundamental Heat Transfer

FY11 – System R&D

FY12 – FY13 Application

FY14 – Demonstration

12

• Air flow rate control • High accuracy heat transfer measurement • Velocity field characterization

– Hotwire anemometry – Particle image velocimetry

• Computer programmable

Cooling Technology Air Cooling Technology Characterization Platform

[1]

[2]

13

Steady and Synthetic Jet Impingement Advanced technology research

Suction Ejection

Square Heater

y

H

S

Nozzle

Steady Jet Synthetic Jet

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

10

20

30

40

50

60

time (ms)

Vel

ocity

(m/s

)

Maximum V =51.08 m/sVmean =17.00 m/s

x

Cen

ter V

eloc

ity a

t 0.5

x D

h (m

/s)

t1

Ejection t2

Suction

Maximum V = 51.2 m/s Vmean

= 17.0 m/s

14

Steady Jet vs. Synthetic Jet Synthetic jet improved heat transfer coefficient by 30%

• Reynolds number calculated using the center-line time-averaged mean velocity

• Developed steady jet heat transfer correlation

• Introduced dynamic Reynolds number concept to collapse steady and synthetic jet data

f

h

kDhNu =Nusselt Number:

Reynolds Number: νhVD

=Re

• He, X., Lustbader, J., Arik, M., Sharma, R. “Characteristics of Low Reynolds Number Steady Jet Impingement Heat Transfer Over Vertical Flat Surfaces.” ITherm 2012. San Diego, CA. May 20 – June 1, 2012. (pending publication)

• Arik, M., Sharma, R., Lustbader, J., He, X.“Comparison of Synthetic and Steady Jets for Impingement Heat Transfer Over Vertical Surfaces.” ITherm 2012. San Diego, CA. May 20 – June 1, 2012. (pending publication)

* Data normalized, pending approval for publications given below

15

Balance-of-System Understand parasitic loads and system coefficient of performance (COP)

• Measure – Fan performance and power – Ducting systems – Module level – Full System level

• Phase I: Build complete in March • Phase II, Noise Measurement:

Build complete in September.

16

Mechanical Package Inverter Case Study - Air Cooled

1/6 of one inverter leg

Air direction

Air direction

[1]

17

1/12 of one inverter leg One inverter leg

[1] [2]

Mechanical Package Inverter Case Study – Liquid Cooled

Application Specification

Power Level

Geometry Restrictions

Package Geometry

Thermal Environment

Package Materials

Package Mechanical Design

Cooling Technology Selection

Cooling Mechanism (Fin, Jet, etc…)

Area Enhancement Geometry

Balance-of-System

Fluid Flow Rate

Flow Path (Series Parallel)

Temperature Constraints Package Thermal

Interfaces

Efficiency Specification Targets

Thermal Load per Package

Unit

Heat Exchanger Performance

(R”th,ha)

Cooling Tech. Performance

(UA)

Package Thermal Performance

Loss Calculation Thermal Design Targets

Cooling Design Targets

Package FEA

Interconnected Calculations

Thermal Performance

Pressure

COP

System-Level Analysis

19

Example air cooling fins

Example liquid cooling

Air-Cooled System Comparison Example design trade-offs

Liquid Cooled, Tinlet = 70°

C

Tj,max = 125°

C

•450 VDC, 400 Arms, 0.5 power factor, and 125°C temperature limit •Power factor adjusted to provide 3:1 heating of IGBT and diode •Assumes capacitor size of 59.5 kW/L (10.53 μF/kW and 1.596e-3 L/μF)

Go/No-Go 0 Proof-of-Principle

Air Cooled, Tinlet = 40°

C

Tj,max = 150°

C Tj,max = 200°

C

Baseline

Tj,max = 125°

C Tj,max = 150°

C

Concept Spreader

20 20

• Device type • Device locations • Electrical duty cycles • Temperature-dependent loss

equations • Inverter efficiency

Thermal Constraints

Full Numerical Design

Thermal Design

Feasibility / Trade-Off

Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Electrical Design

High Temperature Air-Cooled Inverter

y = 0.0362x + 0.7628R² = 0.9982

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

Vf [V

]

Ic [A]

Diode Single Device

25°C

150°C

Linear (Series1)

*

*Chinthavali, M. “Wide Bandgap Materials.” Section 2.1. DOE 2010 Annual Progress Report for Advanced Power Electronics and Electric Motors. Susan A. Rogers. January 2011.

21 21

• Maximum junction temperature

• Coolant temperature

• Heat generation – Efficiency estimate – Analytical method – Switching model

• Heat exchanger thermal requirements

Thermal Constraints


Thermal Design


Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Thermal Constraints


22

Thermal Constraints


Thermal Design


Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Feasibility/Trade-off

Single Fin CFD

Extrapolate system

Add fan


23

Tchip=150°C - 200°C

Feasibility Study: Single-Channel Model Case Conjugate heat transfer model for a single channel

24

Extrapolation for Box Array Target heat dissipation 3.2 kW

• 3 by 3 array

• 9 by 1 array

Chip Temperature [°C] 150 200

Required inlet volume flow rate [cfm] 72 45

Pressure loss [Pa] 768 374

Chip Temperature [°C] 150 200

Required inlet volume flow rate [cfm] 150 102

Pressure loss [Pa] 143 84 0

1

2

3

4

5

0

0.1

0.2

0.3

0.4

0.5

0 50 100 150 200 250 300

Pres

sure

Loss

(kPa

)

CFMH

eat D

issi

patio

n (k

W)

0

1

2

3

4

5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 20 40 60 80 100 120

Pres

sure

Loss

(kPa

)

CFM

Pressure LossHeat Dissipation_150CHeat Dissipation_200C

Hea

t Dis

sipa

tion

(kW

)

Heat Dissipation 150oC Heat Dissipation 200oC

Pressure Loss

25

0

1

2

3

4

5

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450 500

Pres

sure

Dro

p [P

a]

Flow Rate Through 9-Box Array [CFM]

Heat

Dis

sipa

tion

[kW

]

Example System Flow Study 9-by-1 array design, 175°C

Heat

Pressure

26

0

1

2

3

4

5

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450 500

Pres

sure

Dro

p [P

a]


Heat

Dis

sipa

tion

[kW

]


Heat

Pressure Example Fan 50W

Cross point of the fan curve and pressure loss

27

0

1

2

3

4

5

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450 500

Pres

sure

Dro

p [P

a]


Heat

Dis

sipa

tion

[kW

]

Maximum flow rate: 150 cfm


Heat


28

0

1

2

3

4

5

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450 500

Pres

sure

Dro

p [P

a]


Heat

Dis

sipa

tion

[kW

]

Maximum flow rate: 150 cfm

Maximum heat dissipation: 3.5 kW


Heat


Go/No-Go 1

29 29

Thermal Constraints


Thermal Design


Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Thermal Design

Design concept and balance-of-system testing

Model validation and design optimization


30

Device Test Results

100 200 300 400 500 6000

20

40

60

80

100

120

140

Flow Rate [SCFM] ----9 by 1 Array Design

Qch

ip [W

]

150 oC, Center175 oC, Center200 oC, Center150 oC, 5mm175 oC, 5mm200 oC, 5mm

100 200 300 400 500 6005

10

15

20

Flow Rate [SCFM] ----9 by 1 Array Design

Hea

t Tra

nsfe

r Enh

ance

men

t (%

)

Center vs. 5mm

150 oC

175 oC

200 oC

31

Model Validation Less Than 6.5% error between model and experiment

• Chip temperature: 150°C, 175°C, 200°C • 5 W/mK heat transfer coefficient at the exterior walls • 70% thermal contact between device and fin

70%

0

200

400

600

800

1000

1200

1 2 3 4 5 6

Pres

sure

Dro

p (P

a)

Inlet Flow Rate (CFM)

Averaged error =5.2% Pressure U95= ± 0.5 %

40

50

60

70

80

90

100

110

120

130

1 2 3 4 5 6

Out

let T

empe

ratu

re (o C

)


Averaged error = 4.5% Temperature U95= ± 0.12 °C

0

20

40

60

80

100

120

1 2 3 4 5 6

Heat

Dis

sipa

tion

(W)


Test_150CTest_175CTest_200CModel_150CModel_175CModel_200C

Test 150oC Test 175oC Test 200oC Model 200oC Model 200oC Model 200oC

Averaged error =6.5% Power U95= ± 0.5 %

32

Module Design Improvement Parametric study: Chip location

Inle

t Flo

w R

ate

(CFM

)

Dimensionless Chip Location0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

90

100

110

120

130

140

150

160

Minimum inlet flow rate is required. ( L* = 0.47)

L*= Lchip

Lmodule

L*=0.26 L*=0.47 L*=0.74

33 33

Thermal Constraints


Thermal Design


Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Full Thermal Design

• Large conjugate heat transfer model to finalize prototype design

• Couple module model to balance-of-system test results

• Design drawings to build thermal management prototype

• System-level model

High Temperature Air Cooled Inverter Go/No-Go 2

34 34

Thermal Constraints


Thermal Design


Hardware

Elec

tric

al D

esig

n (O

RNL)

Design

Prototype Dev.

Validation

Hardware

• Build prototype thermal management system and test on bench

• Use results to feedback and improve design

• Test 2nd generation with electrical hardware

High Temperature Air Cooled Inverter Go/No-Go 3

35

Proposed Future Work

• FY13 • Build and test air-cooled module-level thermal

management with electrical design from ORNL • Test system-level thermal management system.

Demonstrate with lower power inverter from ORNL • Projected Go/No-Go Decision Point: If projected results

meet the DOE inverter target for volume and weight, pursue full build

• FY14 • Work with ORNL to build and test full air-cooled inverter

system • Projected Go/No-Go Decision Point: If test results meet

the DOE inverter targets for volume and weight, then vehicle-level demonstration will be pursued

36

Summary

• Overcome barriers to adoption of low-cost air-cooled heat sinks for power electronics; air remains the ultimate sink.

• Create system-level understanding and designs addressing advanced cooling technology, balance-of-system, and package thermal interactions; developing solutions from fundamental heat transfer, then system level design, to application − culminating in vehicle-level viability demonstration with research partners.

DOE

Mis

sion

Su

ppor

t Ap

proa

ch

37

Summary

• Showed 30% better heat transfer performance for synthetic jets than steady jets

• Using NREL’s system-level analysis method, found that it may be possible to approach liquid-cooling power density using advanced technology for air-cooling

• Completed device-level test bench, tested baseline fin design, and validated CFD model

• Completed initial design feasibility study

• Strengthened collaboration with ORNL for collaborative high-

temperature air-cooled inverter project • Researching advanced air-cooling technology in collaboration with GE,

Momentive, and Sapa • Interacting with auto OEMs and suppliers for test data, review, and

validation activities

Tech

nica

l Ac

com

plis

hmen

ts

Colla

bora

tions

38

For more information contact: Principal Investigator Jason A. Lustbader [email protected] Phone: (303)-275-4443 APEEM Task Leader Sreekant Narumanchi [email protected] Phone: (303)-275-4062

Acknowledgments:

• Susan Rogers and Steven Boyd U.S. Department of Energy

• Madhu Sudhan Chinthavali Oak Ridge National Laboratory

Team Members:

Kevin Bennion Xin He Charlie King Kyu-Jin Lee Tim Popp Stephen Harmon

Acknowledgments and Contact

39

References Slide 4 1. Honda Insight photograph: John P. Rugh, NREL 2. Honda power electronics photograph: Oak Ridge National Laboratory 3. Electric Mini Cooper photograph: DOE Advanced Vehicle Testing Activity & Idaho National Laboratory 4. AC Propulsion AC-150 photograph: Jason A. Lustbader & Dean Armstrong, NREL Slide 9 1. Synthetic jet photograph: Gopi Krishnan and Charlie King, NREL 2. Micro-fin photograph: Charlie King, NREL 3. Inverter photograph: Mark Mihalic, NREL 4. Inverter photograph: Mark Mihalic, NREL 5. Prius photograph: NREL PIX15141 Slides 10 1. Test bench photograph: Jason A. Lustbader, NREL 2. Constant temperature anemometer, Jason A. Lustbader, NREL Slide 13 1. Air cooling system test bench nozzle chamber: Tim Popp, NREL 2. Air cooling system test bench nozzle chamber: Tim Popp, NREL Slide 14 1. Inverter cold plate: Kevin Bennion, NREL 2. One leg of an inverter: Kevin Bennion, NREL Slides 27-29 1. Device-level test bench setup: Xin He, NREL

Technical Back-Up Slides

(Note: please include this “separator” slide if you are including back-up technical slides (maximum of five). These back-up technical slides will be available for your presentation and will be included in the DVD and Web PDF files released to the public.)

41

Air-Cooled Results Example design trade-offs


Air-Cooled, Tinlet = 40°

C

Tj,max = 200°

C Tj,max = 150°

C Tj,max = 125°

C

Baseline

IGBT Diode

Tj,max

Coolant

Heat Exchanger

•450 VDC, 400 Arms, 0.5 power factor, and 125°C temperature limit •Power factor adjusted to provide 3:1 heating of insulated gate bipolar transistor (IGBT) and diode

42



C

Example Air-cooling fins

Tj,max = 200°

C Tj,max = 150°

C Tj,max = 125°

C

Baseline

Tj,max = 150°C

Tj,max = 125°C

Concept Spreader

IGBT Diode

Tj,max

Coolant

Heat Exchanger

•450 VDC, 400 Arms, 0.5 power factor, and 125°C temperature limit •Power factor adjusted to provide 3:1 heating of IGBT and diode

43



Example liquid cooling


C

Tj,max = 125°

C Tj,max = 150°

C Tj,max = 200°

C

Baseline

Tj,max = 125°

C Tj,max = 150°

C

Concept Spreader

Liquid-Cooled, Tinlet = 70°

C

Tj,max = 125°

C

•450 VDC, 400 Arms, 0.5 power factor, and 125°C temperature limit •Power factor adjusted to provide 3:1 heating of IGBT and diode

44

Steady Jet Nusselt Number Correlations Correlations accurately fit experimental data

44

Dh: nozzle hydraulic diameter a, b, c: least-squares fit based on experimental data Kf: air thermal conductivity

• H/Dh=5

• H/Dh = 10, 15 and 20; y/x ≥ 8

0 500 1000 1500 2000Re

h =

Nu*

Kf/D

h (W/m

2 .k)

H/Dh=10

H/Dh = 15

H/Dh = 20

2nd Order Polynomial Fit

45

Correlating Synthetic and Steady Jet Heat Transfer Dynamic Reynolds number collapses steady and synthetic jet Nusselt number

Dynamic Reynolds Number Conventional Reynolds Number

45

• Unsteady heat transfer coefficient – A function of the changing rate of gas flow – Collapse to the steady jet heat transfer coefficient by introducing dynamic

correction term in Reynolds number • Introducing Dynamic Reynolds number for synthetic jet

C1 is a calibration constant, determined based on the experimental results

0 500 1000 1500 2000 2500Re

Nu

f = 200 Hzf = 300 Hzf = 400 Hzf = 500 Hzf = 600 HzSteady Jet

0 500 1000 1500 2000Dynamic Re

Nu

f = 200 Hzf = 300 Hzf = 400 Hzf = 500 Hzf = 600 HzSteady Jet

air cooling technology for power electronic thermal control · air cooling technology for power...

Documents