( microscale transport ... · enhancing two-phase heat transfer in microchannel flows. experiments...

Purdue University - School of Mechanical EngineeringSuresh V. GarimellaSuresh V. Garimella

• Microscale Transport and Microchannels– Two-Phase Transport of Dielectric Fluids through

Silicon Microchannel Heat Sinks

– Enhancement of Boiling in Microchannels

– Infrared PIV for Non-Intrusive Microfluidic

Measurements

– Micro-scale Temperature Measurement

– Laser-Induced Flourescence Thermography

Measurements of Flow Boiling Heat Transfer

– Inlet Manifold Considerations for Microchannel Heat

Sinks

– Effects of Surface Roughness and Wettability on

Nucleate Boiling Heat Transfer

– The Effects of Surface Roughness on Flow Boiling in

Microchannels

– Numerical Simulation of Condensation in

Minichannels

– Rarified Gas Flow in Microtubes

– Experiments and Models for Two-Phase Transport of

Water in Microchannels

– Non-intrusive Microscale Temperature

Measurements

– Single-Phase Microchannel Heat Sinks

– System-level Analysis of Microchannel Heat Sinks

– Microchannel Inlet Manifold Analysis

Dr. Suresh V. Garimella Research Program

Director of Cooling Technologies Research Center(https://engineering.purdue.edu/CTRC)

• Electrically Actuated Microscale Flows − Microscale Ion-Driven Air Flow

− Micromechanical Electrohydrodynamic Pump

− Microscale Ionic Winds for Local Heat Transfer

Enhancement

− Microscale Electromechanical Flow Actuation

− Modeling of Microscale Electrohydrodynamics

• Thin-Film Transport, Wicks and Heat Pipes− Fundamental Experimental Investigation of Thin-

Film Evaporation

− Reverse-engineer Microstructures for Optimal

Thin-Films

− Thin Film Evaporation in V-groove Geometry

− Transport in Wick Sturctures

− 3-D Transient Models for Miniature Flat Heat Pipes

− Characterization of Heat Pipe Wick Fluid Transport

and Thermal Performance

− Heat Transfer During Evaporation of Binary

Liquids from Wick Microstructures

− Numerical Modeling of 3D Vapor Chambers

− Characterization of Composite Heat Spreaders

− Theory of Thin-Film Evaporation

− Modeling of Flow Boiling and Thin Film

Evaporation using the Material Point Method


• Novel Air Cooling Approaches – Two Phase Liquid Jet Impingement Cooling

– Fluid-Structure Interaction in Vibrating Cantilevers

– Thermal-Fluidic Performance of Piezoelectric Fans

– Miniature Piezoelectric Fans

– Reduction of Noise Emissions from Small Fans

– Confined and Submerged Jet Impingement

– Waste Heat Recovery

• Thermal Materials R&D – Transport in Porous Foams

– Phase Change Energy Storage

– Analysis of Transport in Porous Microstructures

– Low-Temperature Synthesis and Bonding of CNT

Thermal Interfaces

– Carbon Nanotube Electrical Interfaces for

Thermoelectrics

• Thermal Interfaces– Thermal Analog to AFM Force-Displacement

Measurements for Interfacial Contact Resistance

– Low-Temperature Synthesis and Bonding of

Carbon Nanotube Thermal Interfaces

– Thermomechanical Modeling of Thermal Contact

Conductance

– Thermal Contact Conductance Measurements

Dr. Suresh V. Garimella Research Program(Continued)

• Thermal Interfaces (continued)– Particulate Thermal Interface Materials

– Compliant Thermal Interface Adhesives

• Small-scale Refrigeration – Refrigerant Flow Boiling in Microchannels

– Miniature Diaphragm Compressors for Electronics

Cooling

– Miniature Linear Compressors for Electronics

Cooling

– Miniature Vapor Compression for Electronics

Cooling

• Exploratory and Novel Concepts – Electrical Actuation of Droplets for Microelectronics

Cooling

– Droplet Actuation and Motion under various

Actuation Forces

– Alternative Heat Rejection Methods for Power

Plants

– Thermal Ratcheting Prevention of a Molten-Salt

Thermocline

– Electroosmotic Pumping through Porous Anodic

Alumina Templates

– Bridgman Growth in a Transparent Material

– Direct Cooling by Electron Field Emission

– Microscale Electromechanical Flow Actuation

– Solar Thermal Energy Storage


Two-Phase Transport of Dielectric Fluids in Silicon

Microchannel Heat Sinks

Faculty: S. V. Garimella Student: Tannaz Harirchian

Approach

Selected

Publications

Objective

Investigate boiling phenomenon in micro scale

Perform high-speed visualizations

Conduct local measurements of wall temperature & heat flux

T. Harirchian and S. V. Garimella, ASME

Journal of Heat Transfer Vol. 130,

080909, 2008.

T. Harirchian and S. V. Garimella,

International Journal of Heat and Mass

Transfer Vol. 51(15-16), pp. 3724-3735,

2008.

T. Chen and S. V. Garimella, Int J

Multiphase Flow, 32:957-971, 2006.

T. Chen and S. V. Garimella, IEEE

Transactions on Components and

Packaging Technologies Vol. 30, pp. 24-

31, 2007.

Explore, quantify and model

boiling heat transfer in silicon

microchannel heat sinks

using dielectric fluids.

microchannel width=400µm

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 50 100 150 200 250 300

q" (kw/m2)

h (

w/m

2K

)

250

700

1150

1600

kg/m2s

kg/m2s

kg/m2s

kg/m2s

Microchannels

Heaters,

PCB

Underfill

Solder bumps (Pb/Sn)

NOT TO SCALE

passivation layertemperature sensors,

Can achieve extremely high heat transfer rates

Provides the ability for chip-integration

Impact


Enhancement of Boiling in Microchannels

Faculty: S. V. Garimella Students: B. J. Jones and J. P. McHale

Impact

Approach

Selected

Publications

Objective

Develop a better understanding of the role of surface

effects on boiling in microchannels

Develop techniques to enhance the boiling process in

microchannels

To develop techniques for

enhancing two-phase heat

transfer in microchannel

flows.

Experiments are performed using flat surfaces (pool boiling) and

microchannels (flow boiling) with varying surface characteristics.

B. J. Jones and S. V. Garimella,

ASME-JSME Thermal Engineering

Summer Heat Transfer Conference,

HT2007-32230, Vancouver,

Canada, July 8-12, 2007.

Pool boiling curves for surfaces with

varying roughness.

Polished Surface EDM Surface

Experimental Setup

Microchannel Test Piece


Infrared Micro-Particle Image Velocimetry for Non-Intrusive Microfluidic

Measurements

Faculty: S. V. Garimella Student: B. J. Jones

Impact

Approach

Selected

Publications

Objective

Extends the capabilities of particle image velocimetry, allowing

for the measurement of flow fields inside silicon microdevices

This technique is ideally suited for measuring flow patterns

inside silicon microchannel heat sinks, without optical access

Develop a novel, non-intrusive

diagnostic technique for

measuring sub-surface fluid

flows in silicon microdevices

The principles of particle image velocimetry are employed using

infrared light. Silicon is transparent to wavelengths > 1200 nm

IRPIV System Layout

B. J. Jones, S. V. Garimella, 13th Int

Heat Trans Conf, EXP-07, Sydney

Australia, 2006.

D. Liu, S. V. Garimella, S. T.

Wereley, Exp in Fluids, 38: 385-392,

2005.Velocity Measurements

inside Microtube

PIV Image Capture

Purdue University - School of Mechanical EngineeringSuresh V. Garimella

Measurement of Brownian motion of suspended particles is used to extract temperature information from low-speed, steady flows. A novel technique is being developed to measure temperature at higher velocities.

2222

, /)8(2 tDMds eco 20

30

40

50

60

70

80

90

20 40 60 80Measured temperature (

oC)

Te

mp

era

ture

usi

ng P

IV (

oC

)Shows the effect of Brownian motion in PIV analysis

and the equation that relates it to temperature.

Plots shows the measured temperature vs the

actual temperature. Uncertainty involved in

the method is ±1 K.

22

, /2 eco ds

Micro-scale Temperature measurement

Faculty: S. T. Wereley and S. V. Garimella Student: P. Chamarthy

Novel non-intrusive temperature measurement technique to be applied in microchannels

Micro-scale Temperature measurement

Faculty: S. T. Wereley and S. V. Garimella Student: P. Chamarthy

Objective

Approach


Explore the heat transfer mechanisms

associated with single bubble growth

under forced-convection conditions using

a laser-induced fluorescence

thermography technique.

B.J. Jones and S.V. Garimella,

Laser-induced fluorescent

thermography measurements of

nucleate flow boiling, 14th IHTC,

2010 (submitted abstract).

B.J. Jones and S.V. Garimella,

Measurements of temperature

field around a growing vapor

bubble using laser-induced

fluorescence thermography,

ITherm, 2010 (abstract accepted).

Experiments will further elucidate the

important heat transfer mechanisms occurring

during nucleate flow boiling.

Develop a laser-induced fluorescence

measurements system for studying

temperature fields around a growing vapor

bubble

Conduct measurements and analysis to

ascertain the important mechanisms behind

nucleate flow boiling heat transfer

LIFT Calibration Cell

LIFT Optical System

Test Section Design

LIFT Images – Before & After Boiling

Laser-Induced Fluorescence Thermography Measurements of Flow

Boiling Heat Transfer


Objective

Impact

Approach

Selected

Publications


Inlet Manifold Considerations for Microchannel Heat Sinks


Impact

Approach

Selected

Publications

Objective

Develop an understanding of underlying causes of flow

maldistribution

Develop guidelines to avoid flow maldistribution in

microchannel heat sinks

To study effects of inlet

manifold designs on flow

maldistribution in

microchannel heat sinks.

Numerical simulations are used to predict the

fluid behavior inside a microchannel heat sink,

and are validated against experimental (IR-

PIV) measurements.

B. J. Jones, P. S. Lee, and S. V.

Garimella, International Journal of

Heat and Mass Transfer, Vol. 51,

pp. 1877-1887, 2008.

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38

Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

Re = 10.2

Re = 102

Exp.

Num.

1 38Channel Number

Ma

ss

Flu

xR

atio

,u

c/m

c"

10 20 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

1 38

Manifolds

Channels

Velocity Contours and Streamlines

Comparison of Numerical

Results to IRPIV Experiments


Quantify the effect of random surface

roughness on nucleate boiling

characteristics for a variety of

conditions.

Quantify bubble nucleation characteristics

from realistic surfaces in a statistically

meaningful way

Improve modeling of nucleate boiling heat

transfer

Assist in improved modeling of two-phase

flow at the microscale

Develop high-speed digital measurement

techniques for bubble geometry near surfaces

Wall Superheat, Tw

- Tsat

(K)

He

at

Flu

x,q s

(kW

/m2)

0 5 10 15 20 25 30 35 400

20

40

60

80

100

Polished 0.03 m - q

Polished 0.03 m - q

EDM 1.08 m - q

EDM 1.08 m - q

EDM 2.22 m - q

EDM 2.22 m - q

EDM 10.0 m - q

EDM 10.0 m - q

Random surface roughness

produced by consistent

method

Wide range of surface

roughness

Working fluids include

different wetting

characteristics

Effects of Surface Roughness and Wettability on Nucleate Boiling Heat

Transfer

Faculty: Suresh V. Garimella Student: John P. McHale

Objective

Approach

Impact


Conduct exploratory experiments on

the effect of surface roughness in

microchannels.

B.J. Jones, and S.V. Garimella, Surface

roughness effects on flow boiling in

microchannels, ASME Journal of Thermal

Science and Engineering Applications, (in

review).

B.J. Jones and S.V. Garimella, Surface

roughness effects on boiling heat transfer,

IMAPS Advanced Technology Workshop and

Tabletop Exhibition on Thermal Management,

Palo Alto, CA, October 5-8, 2009.

B.J. Jones and S.V. Garimella, Surface

roughness effects on flow boiling in

microchannels, 2009 InterPACK, San

Francisco, CA, July 19-23, 2009, paper no.

IPACK2009-89168.

Surface roughness has a notable

impact on flow boiling heat transfer and pressure drop

Considering the typical uncertainties in flow boiling correlations,

the added uncertainties due to surface roughness do not lead to a

significant loss in predictive accuracy

Develop method of producing microchannel

surfaces of varying roughness

Conduct experiments to establish the

dependence of surface roughness on heat

transfer and pressure drop

Evaluate the suitability of flow boiling

correlations over a wide range of roughness

(a) G = 200 kg/m2s (b) G = 600 kg/m2s (c) G = 1000 kg/m2s

Figure 8. Influence of surface roughness on channel pressure drop at different mass fluxes.

XXX

Heat Flux, q (kW/m2)

Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX


Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

X

XX


Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX


Figure 8. Influence of surface roughness on channel pressure drop at different mass fluxes.

XXX


Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX


Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

X

XX


Pre

ssu

reD

rop

,

Pc

(kP

a)

0 1000 2000 30000

20

40

60

80

100

120

140

160 Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX

Pressure

Drop

Saw Cut EDM


X

XX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX

X

XX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

Figure 7. Influence of surface roughness on saturated heat transfer coefficients at different mass fluxes.


X

XX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX

X

XX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

CHFX


He

at

Tra

nsfe

rC

oe

ffic

ien

t,h

sa

t(k

W/m

2K

)

0 1000 2000 30000

20

40

60

80

100

120

Ra

= 1.4 m

Ra

= 3.9 m

Ra

= 6.7 m

Figure 7. Influence of surface roughness on saturated heat transfer coefficients at different mass fluxes.

Heat Transfer Surface Map

Flow LoopTest Section

Test Piece

The Effects of Surface Roughness on Flow Boiling in Microchannels


Objective

Approach

Impact

Selected

Publications


Numerical Simulation of Condensation in Minichannels

Faculty: S. V. Garimella Student: E. Da Riva

Impact

Approach

Objective

Study the condensation

process inside minichannels

with different geometries

Direct tracking of the vapour-

liquid interface by means of

the VOF method

-0.5 -0.25 0 0.25 0.50

1

2

3

4

5

6

y [mm]

Axia

l ve

locity [

m/s

]

AXIAL VELOCITY PROFILE

CIRCULAR CHANNEL

VAPOUR-LIQUID INTERFACE

IN SQUARE CHANNEL

Refrigerant charge minimization is one of the most

important targets for HVAC applications to cope with the

new environmental challenges

Minichannels appears to be a good opportunity to

minimize the charge in HVAC without loss in energy

performance


Rarefied gas flow is important for:

Gas dynamics in high vacuum environments – orbital science,

vacuum pump, etc.

Compressible gas flow in micro/nano-structures

Develop a model that can

predict mass flowrate and

streamwise pressure

distribution of rarefied gas

flows in microtubes

Mass flowrate

o

oo

oo

bKn

bKnPKnbP

KnP

RTL

prQ

1ln1

4

4

8

1

2

22

0

24

0

Pressure distribution

o

o

oo

o

o

oo

bKn

bKnPKnPbPPKnP

bKn

bKnpKnpbppKnp

x

1ln81421

1ln81421

122

22

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

0 10 20 30 40

Experiment

Theory

Valve #1 Valve #2

Voltage reader Microscope

Meniscus

Enclosed gas reservoir

Capillary tube

Thermocouples

Valve #3

Filter

Pa

Rarefied Gas Flow in Microtubes

Faculty: S. V. Garimella Post-doc: Z. Yang

Objective

Approach

Impact

Results &

Comparisons


Microscale Ion-Driven Air Flow

Faculty: S. V. Garimella, T. S. Fisher ; Students: V. Bahadur, W. Zhang, D. Schlitz, M. Peterson

Objective

Approach

Selected

Publications

Impact


Micromechanical Electrohydrodynamic Pump

Faculty: S. V. Garimella Student: B. D. Iverson

Impact

ApproachSelected

Publications

Objective

Chip-integration of micro-scale pumping can:

Increase power dissipation while maintaining small form factor

Significantly reduce packaging thermal resistance

Provide flexibility in component constraints and layout

B. D. Iverson and S. V. Garimella,

Microfluidcs and Nanofluidics, DOI

10.1007/s10404-008-0266-8

V. Singhal and S. V. Garimella, IEEE

Transactions on Advanced Packaging, vol.

28, pp. 216-230, 2005.

V. Singhal, S. V. Garimella, and A. Raman,

Applied Mechanics Reviews, vol. 57, pp.

191-221, 2004.

Design and fabricate a pump

that is scalable to the micro-

domain for liquid pumping

and electronics cooling

Piezoelectric

Patch

Diaphragm with

Electrodes

Channel

Substrate

Combined

StackHeat Flux

(Active Device)

Enhance induction EHD with fluid

motion from a vibrating diaphragm.

Charge Clouds

Increasing Electrical Conductivity

+ V + V/2+ V/2- V - V/2- V/2

Fluid Velocity

Traveling-wave sinusoid

Heat Flux

Bus bars and electrodes

Microfabricated channels


position [m]

T[o C]

-400 -200 0 200 400

40

40.5

41

Tbottom

tb_left

T_b_right

Tmean

tavg-

tavg+

Ttop

T_f+error

T_f-error

Liquid

Region

Dry

Region

Constant

heat flux

quartz

substrate

Fundamental Experimental Investigation of Thin-Film Evaporation Faculty:

S. V. Garimella and J. Y. Murthy Student: H. K. Dhavaleswarapu

Impact

Approach

Selected

Publications

Objective

H. K. Dhavaleswarapu , P.

Chamarthy, S. V. Garimella, and J.

Y. Murthy, Physics of Fluids,19,

2007.

H. K. Dhavaleswarapu, S. V.

Garimella, and J. Y. Murthy

IMECE2007-42398, Seattle WA.,

2007.

P. Chamarthy H. K.

Dhavaleswarapu, S. V. Garimella,

J. Y. Murthy and S. T. Wereley,

Experiments in Fluids, 44, 2008.

Develop a comprehensive

understanding of the transport

phenomena occurring at the

thin liquid film near the

contact line

Thin-film region associated with very high heat transfer rates

Provide accurate measurements of thin-film evaporation rates

and thermocapillary convection which is critical for boiling and

heat pipe design

Develop methods for sustaining and enlarging thin-film area

Temperature suppression in the thin-

film region indicating its high efficiency

Thin-film evaporation in a V-groove

investigated through microscale

infrared temperature measurements

Temperature valley

indicating high

efficiency of thin-film

region

~2.5K

~17.5K

Line

BB

Dry

region

Liquid

Film

V-GrooveMeniscus

Thin-film region

Meniscus

Wall temperature along Line BB

Dry region

Liquid Film

Edge of the

substrate

IR

cameraImaged

area

(c)‏

Heptane meniscus in a

500 μm channel

Wall temperature along V-groove

Wall temperature near thin-film region


• Optimization of the performance of evaporator in a two-phase

cooling device

• Capability to remove ultra-high heat flux in electronics by

optimizing the microstructure based on developed models

R. Ranjan, S V. Garimella and J. Y. Murthy,

ASME 2008 Summer Heat Transfer

Conference, Paper no. HT2008-56170.

H. Wang, J. Y. Murthy, S V. Garimella,

IJHMT, 2007, vol. 50, pp. 3933-3942

H. Wang, J. Y. Murthy, S V. Garimella,

IJHMT, 2008, vol. 51, pp. 3007-3017

Develop physics-based models

to analyze wicking, permeability,

thermal conductivity and thin-

film evaporation characteristics

of microstructures

Compute liquid meniscus shapes in

microstructures

Packed bed of spheres

(sintered particles)

Horizontal wires (wire mesh)

Model evaporation from liquid meniscus in

microstructures

Superheated solid wall

Liquid-vapor

interface

Liquid inlet

90% of the evaporation occurs from

the thin-film region

Reverse-engineer Microstructures for Optimal Thin-Films

Faculty: J. Y. Murthy, S. V. Garimella Student: Ram Ranjan

ObjectiveImpact

Approach

Selected

Publications


Thin film evaporation in V-grooves will:

Enhance understanding of the physics of thin film evaporation

Enable better design of heat pipes

Investigate heat transfer from

evaporating meniscus in V-

grooves

Experiment and Modeling

Dark region in temperature

profile indicates lower

temperature near contact line

due to thin film evaporation

liquid

wallqappliedModeling efforts will focus on

the 3D flow and temperature

fields in the V-groove

Temperature contours Flow field

Wall temperature map

Thin Film Evaporation in V-groove GeometryFaculty: S. V. Garimella Student: C. P. Migliaccio

Objective

Approach

Impact


Transport in Wick Structures

Faculty: S. V. Garimella Student: Brian Iverson and Tyler Davis

Impact

Approach

Selected

Publications

Objective

B. D. Iverson, T. W.

Davis, S. V. Garimella,

M. T. North, and S.

Kang, AIAA Journal of

Thermophysics and

Heat Transfer Vol. 21,

No. 2, pp. 392-404,

2007.

T. W. Davis and S. V.

Garimella,

Experimental Heat

Transfer, Vol. 21(2), pp.

143-154, 2008.

Experimentally determine the

performance of wicks under

typical heat pipe operating

conditions

A better understanding of the

performance and limits of operation of

heat pipe wicks is essential for design

improvements and miniaturization efforts.

Two novel setups are

developed to evaluate

heat pipe wicks in

environments typical of

operating conditions

(partially saturated,

evacuated), and

measure mass flow rate

and wick conducitivity

HeaterClamp

Condensate

Collection

Annulus

Liquid

Pool

WickConical

Cap

Thermocouple

Pass-throughVacuum

Pressure

Gage

Depth

Width

Length

(b)(a)

(c)


• Determine the capillary fluid transport properties of

porous wick materials

• Parametrically characterize the thermal performance

of conventional sintered copper powder and screen

wick materials

• Investigate the possible thermal performance

enhancement due to integration of carbon nanotubes

into conventional wick structures

• Optimize heat pipe wick design for minimum

thermal resistance

vapor flow

capillary wicking

Condenser Side

boiling/evaporation

porous wick material

Heat Pipe Thermal Spreader

Capillary Wicked Boiling and

Evaporation Test Facility 0

100

200

300

400

500

600

0.0 15.0 30.0

Tsubstrate - Tref (C)

He

at

Flu

x (

W/c

m2)

Thermal Performance

Characterization: Boiling Curve

Sintered Copper Powder

SEM Image

Numerical Modeling Optimization of

Mass Transport for a Nanostructured

Wicking Surface

Cu Powder

Test Sample

FEM Grid Geometry

Fluent Flow Solution

Characterization of Heat Pipe Wick Fluid Transport and Thermal

PerformanceFaculty: S. V. Garimella Student: Justin Weibel

Approach

Objective


Wang, H., Murthy, J. Y., and Garimella, S. V., 2007,

“Transport from a Volatile Meniscus inside an Open

Microtube”, Int. J. Heat and Mass Transfer , 51, pp.

3007-3017.

Dhavaleswarapu, H. K., Chamarthy, P., Garimella, S. V.,

and Murthy, J. Y., 2007, “Experimental Investigation of

Steady Buoyant-Thermocapillary Convection near an

Meniscus”, Physics of Fluids, 19, pp. 082103.

Ranjan, R., Murthy, J. Y., and Garimella, S. V., 2009,

“Analysis of the Wicking and Thin-film Evaporation

Characteristics of Wick Microstructures”, ASME J. Heat

Transfer, 331, pp. 1-10.

Dalal, A., Ranjan, R., Murthy, J. Y., and Garimella, S.

V., “Heat Transfer during Evaporation of Binary Liquids

in Wick Microstructure”, 2010 ISHMT-ASME Heat and

Mass Transfer Conference, IIT Bombay, Mumbai, India.

The addition of 1-propanol is found to increase the overall evapoartion rate

and hence the overall heat transfer

It is found that the water evaporation rate exhibits a maximum at 3.26% mass

fraction (Y); correspondingly, the heat flux also exhibits a maximum at this

value

Development of a numerical

model for computing the

evaporation of binary liquids

from wick microstructures under

saturated vapor conditions. Geometry of the problem

User -Defined functions have been developed in

Fluent to implement the evaporation model

The shape of the liquid-vapor interface in the wick

structure is obtained using Surface Evolver

The binary fluid mixtures contains water-liquid and 1-

propanol-liquid as species

The wick is made of copper

Heat Transfer During Evaporation of Binary Liquids from Wick

Microstructures

Faculty: S. V. Garimella and J. Y. Murthy Postdoc: Amaresh Dalal

Objective

Results

Evaporative

Model

Selected

Publications


• Micro-level effects (thin-film evaporation, Marangoni convection)

are captured in the vapor chamber model

• Vapor chamber performance with different wick structures can be

predicted using the coupled model

Develop physics-based numerical

models to determine the dry-out of

vapor chamber heat spreaders for

different wick structures.

Couple Evaporation Micromodel

with Vapor Chamber 3D Model

3D Vapor Chamber Simulation Results

Temperature Contours

Particle Paths

Compute pressure gradient across interface in the

device

Compute interfacial mass transfer

coefficient including thin-film evaporation and Marangoni effects

Get corresponding contact angle from

Surface Evolver model

Macromodel1

Surface Evolver

Model2

Evaporation

Micromodel3

[1] R. Ranjan, J. Y. Murthy and

S. V. Garimella, 2010 ITHERM

Conference, Paper no.

ITHERM10-2586..


S. V. Garimella, ASME JHT,

2009, vol. 131, 101001.


S. V. Garimella, ASME IMECE

2009, Paper no. IMECE09-

11326.

[4] U. Vadakkan, S. V.

Garimella and J. Y. Murthy,

ASME JHT, 2004, vol. 126,

347-354.

Numerical Modeling of 3D Vapor Chambers

Faculty: J. Y. Murthy, S. V. Garimella Student: Ram Ranjan

Objective Impact

ApproachSelected

Publications


Plasma enhanced chemical

vapor deposition of CNTs

3-D method for thermal

characterization

Optimization of CNT growth

parameters and materials

selection for composites

Low temperature growth and optimization of CNT growth parameters on composites

Establishment of robust thermal characterization strategy for multi layered materials

Combining industrial composite manufacturing with direct growth of CNTs will yield a cost-effective solution to replace copper with high conductivity composite heat spreaders and interfaces.

J. Xu and T.S. Fisher, Int. J. Heat Mass

Trans. 49 1658 (2006).

X. Hu, A.A. Padilla, J. Xu, T.S. Fisher,

K.E. Goodson, J. Heat Transfer, 118

(11) 1109 (2006).

D.G. Cahill, Rev. Sci. Inst. 61 (2) 802

(1990).

K. Goodson, O. Kading, M. Rosler R.

Zachai, J. Appl. Phys. 77 (4) 1385

(1994).

Low cost manufacture of diamond-metal composites has become commercially viable

Leverage group’s expertise and industry partnership for carbon nanotube (CNT) synthesis on composites

V +ve

I +veI -ve

V -ve

Composite substrate

Deposited 3- element

Characterization of Composite Heat Spreaders

Faculty: T.S. Fisher S. V. Garimella Student: S. V. Aradhya

Objective Technical Challenges

Approach Selected PublicationsMethod for Conductivity


Develop a comprehensive evaluation

of two-phase liquid jet impingement

cooling in confined conditions and

provide guidelines for optimal design.

The study will provide:

Evaluate correlation in the literature with experimental data

Provide optimal nozzle plate design for a given height for two phase

cooling

Improve details on cross flow affects between nozzle jets

Perform experimental measurements

Compare data to established correlations

Develop an optimization study with

experimental dataD.E. Maddox and A. Bar-Cohen, “Thermofluid Design of

Submerged-Jet Impingement Cooling for Electronic Components,”

ASME, Heat Transfer Div Publ HTD, Vol. 171, pp. 71-80, 1991

D. Copeland, “Enhancement of Direct Liquid Cooling of Electronics

Doctor of Engineering (DrEng) thesis,” Department of Mechanical

and Intelligent Systems Engineering School of Engineering, Tokyo

Institute of Technology Adviser: Professor Wataru Nakayama,

February 1996

T. Brunschwiler, H. Rothuizen, M. Fabbri, U. Kloter, and B. Michel,

“Direct Liquid Jet-Impingement Cooling with Micron-Sized Nozzle

Array and Distributed Return Architecture” IEEE 2006

S. V. Garimella, “Heat Transfer and Flow Fields in Confined Jet

Impingement,” Chapter 7, Annual Review of Heat Transfer, Vol. XI,

pp. 413-494, 2000.

Two Phase Liquid Jet Impingement Cooling

Faculty: S. V. Garimella Student: D. A. West

Objective

Approach

Impact

Selected

Publications


X (m)

Y(m

)

0.02 0.06 0.10

0.01

0.02

0.03

0.04T. Acikalin, S. V. Garimella, A. Raman and J. Petroski, International Journal of Heat and Fluid Flow Vol. 28(4), pp. 806-820, 2007.

T. Açıkalın, A. Raman and S. V. Garimella, J. Acoust. Soc. Am., 114 (4): 1785-1795, 2003.

T. Açıkalın, S.M. Wait, S.V. Garimella and A. Raman, Heat Trans. Eng. 25(1): 4-14, 2004.

Develop analytical and numerical models to predict fluid-structure interaction of vibrating cantilevers.

This research will help place piezoelectric fans in the thermal management toolkit by providing insight into the fluid flow induced by these devices.

2-D streaming model for a baffled piezoelectric fan

aggress well experimental flow

visualization

Develop analytical and numerical models to predict fluid-structure interaction of vibrating cantilevers.

Experimental flow visualization

Piezoelectric fans

Numerical CFDmodels

Streaming flow models

Fluid-Structure Interaction in Vibrating Cantilevers

Faculty: Suresh V. Garimella Student: Tolga Açıkalın

Objective

Approach

Impact

Selected

Publications


• M. Kimber, S. V. Garimella and A. Raman, ASME

Journal of Heat Transfer Vol. 129, pp. 1168-1176,

2007.

• T. Acikalin, S. V. Garimella, A. Raman and J.

Petroski, International Journal of Heat and Fluid

Flow Vol. 28(4), pp. 806-820, 2007.

• M. Kimber, S.V. Garimella and A. Raman,

IMECE2006-13922, Chicago, Il, 2006.

• T. Açıkalın, S.M. Wait, S.V. Garimella and A.

Raman, Heat Trans. Eng. 25(1): 4-14, 2004.

Develop physics-based models to describe and predict performance of piezoelectric fans in single and array configurations.

This research is helping place piezoelectric fans in the thermal management toolkit by providing insight into underlying physics of vibrating cantilevers, and offering predictive tools for design and optimization.

A

Piezoelectric

Fan #1

GP Piezoelectric

Fan #2

y

x

Contours of local convection coefficients with A = 10 mm.

G/A = 0.01

Tw

o-F

an

Exp

erim

ents

G/A = 0.50 G/A = 2.0

G/A = 0.01, P/A = 1.0 G/A = 0.01, P/A = 1.25 G/A = 0.01, P/A = 4.0

Sin

gle

-Fan

Exp

erim

ents

Correlation describes

area-averaged

performance for single fan

10 20 30 40 50 60 70 80 90W/m2K

Thermal-Fluidic Performance of Piezoelectric FansFaculty: Suresh V. Garimella Student: Mark Kimber

Objective Approach

Impact

Selected Publications


Miniature Piezoelectric Fans

Faculty: Suresh V. Garimella Student: Mark Kimber


Transport in Porous Foams

Faculty: S. V. Garimella, Jayathi Murthy Student: S. Ravi Annapragada

Impact

Approach Selected

Publications

Objective

Use of foams for

heat exchange leads to:

• Reduced weight due to low effective density

• Greater heat transfer area due to high surface area/volume

•First-of-its-kind direct numerical representation of foams

• S. Krishnan, J. Y. Murthy

and S. V. Garimella, ASME J

Heat Transfer 127:995 -

1004, 2005.

• S. Krishnan, J. Y. Murthy,

and S. V. Garimella, ASME J

Heat Transfer, 128:793-799,

2006.

• S. Krishnan, S. V. Garimella

and J. Y. Murthy, ASME

IMECE2006-14044, Chicago,

IL, November 2006.

Study transport through open-

celled foam structures for heat

transfer enhancement, via

experiments and unit-cell models

X

X

X

X

X

X

X

X

X

X

XX

Reynolds Number (ReK)

Fri

ctio

nF

acto

r(d

P/d

xK

1/2/(

um

ea

n2))

10-2

10-1

100

10110

-1

100

101

Paek et al.0.105 + (1/Re

K)

Vafai & Tien0.057 + (1/Re

K)

BCC: > 0.94

A15: 0.8 < < 0.96

FCC: 0.83 < < 0.95X

X

X

X

X

X

X

X

X

X

XX

Reynolds Number (ReK)

Fri

ctio

nF

acto

r(d

P/d

xK

1/2/(

um

ea

n2))

10-2

10-1

100

10110

-1

100

101

Paek et al.0.105 + (1/Re

K)

Vafai & Tien0.057 + (1/Re

K)

BCC: > 0.94

A15: 0.8 < < 0.96

FCC: 0.83 < < 0.95

_=

_=

Cube BCC Final Geometry

WP ModelFCC ModelBCC Model


Study transport through real

random porous media for heat

transfer enhancement via direct

CFD computations

• First of its kind analysis of porous

media, employing µ-CT

• Development of 1D analytical models

based on microstruture

• Correlations for predicting flow and heat

transfer

+

Heat Pipe Micro CT • Bodla K. K., Murthy J. Y., and Garimella S. V., 2010,

“Microtomography-Based Simulation of Transport

through Open-Cell Metal Foams,” J. NHT, Part A:

58(7)

• Bodla K. K., Murthy J. Y., and Garimella S. V., 2010,

“Resistance network-based thermal conductivity

model for metal foams,” J. COMMAT, 50(2)

• Bodla K. K., Murthy J. Y., and Garimella S. V.,

“Direct

Simulation of Thermal Transport through Sintered

Wick Microstuructures”, J. Heat Transfer (in review)

Analysis of Transport in Porous Microstructures

Faculty: J. Y. Murthy, S. V. Garimella, Student: Karthik K. Bodla

Objective

Approach

Impact

Selected

Publications


Use of heated AFM tips for interfacial

characterization:

Enables nanoscale spatial resolution

Reduces contrast from variance in tip contact

Provides sub-surface resistance measurement

Develop a method for

measurement of interface

resistance through thin-film

polymer/Si interfaces using a

heated AFM tip.

Measure voltage imbalance in

and out of contact with a

substrate.

Estimate

contribution of

contact

resistance at zero

film thickness.

Identify impact of film thickness on thermal diffusion.1

Calibrate voltage change as a function of

temperature difference.

Thermal Analog to AFM Force-Displacement Measurements for Interfacial

Contact Resistance Faculty: J. E. Blendell and S. V. Garimella Student: B. D. Iverson

Objective

Approach

Impact


• Obtaining thin glass layers with requisite

composition on metal substrates

• Bonding of CNTs with the glass layer

• Scaling of integrated devices on electronic chips demands

improved methods to conduct heat away

• Minimize the thermal contact resistance between CNT tips

and opposing surface for better TIMs

Flow-Temperature Synthesis and Bonding of Carbon Nanotube Thermal

Interfaces Faculty: T. S. Fisher and S. V. Garimella Student: S. V. Aradhya

Objective Technical Challenges

Minimizing the thermal contact resistance between free tips of CNTs and their

opposing substrate allows for the full utilization of the high conductance of CNTs.

Approach

CNT synthesis by plasma

enhanced chemical vapor

deposition

Spin coating of layers on Si

wafers

In-house bonding setup

1-D Reference bar method to

measure thermal contact

resistance

Non-ideal CNT free tip contact

Selected

Publications

B.A. Cola, J. Xu, C. Cheng, H. Hu,

X. Xu, and T.S. Fisher, J. Appl. Phys.

submitted (2006).

J. Xu and T.S. Fisher, Int. J. Heat

Mass Trans. 49, 1658 (2006).

H.J. Quenzer, C. Dell, B. Wagner,

IEEE Micro Electro Mechanical

Systems proceedings (1996).


Thermomechanical Modeling of Thermal Contact Conductance

Faculty: S. V. Garimella Student: C. T. Merrill, A. F. Black, V. Singhal

Objective

Approach

Impact

Selected

Publications


Thermal Contact Conductance Measurements

Faculty: S. V. Garimella Student: C. T. Merrill, P. Litke, A. Black

Objective Impact

Approach Selected

Publications


Refrigerant Flow Boiling in MicrochannelsFaculty: E. A. Groll and S. V. Garimella Student: S. S. Bertsch

Impact

Approach Selected

Publications

Objective

Experimentally determine the

local heat transfer coefficient

in refrigerant flow boiling in a

cold-plate evaporator with

parallel microchannels.

Liu D., Lee P., and Garimella S.V., Int. J.

Heat and Mass Transfer 48:5134-5149,

2005.

Lee P.S. and Garimella S.V., Int. J. Heat

and Mass Transfer, 51:789-806.

Chen, T. and Garimella, S. V., ASME J.

Electronic Packaging 128:398-404, 2006.

Chen, T. and Garimella, S. V. Int. J.

Multiphase Flow 32:957-971, 2006.

Liu, D. and Garimella, S.V. ASME J Heat

Transfer 129:1321-1332, 2007.

S. S. Bertsch, E. A. Groll and S. V.

Garimella, International Journal of Heat

and Mass Transfer Vol. 51, pp. 4775-

4787, 2008.

Bertsch, S.S., Groll, E.A., and Garimella,

S.V., Int. Congress on Refrigeration,

Beijing, China, 2007.

The outcomes of this study will:

assess existing models against experimental results

help formulate predictive correlations for flow boiling

in microchannels

optimize design of microchannel cold plate evaporators

improve simulations of small-scale refrigeration systems

Perform well defined measurements

Compare data to established correlations

Develop new widely applicable correlation

Microchannel

cross-section

Boiling curve

Heat transfer coefficient vs. quality


The diaphragm compressor simulation model is

• Among the few to simulate refrigerant compression

• The first model to simulate diaphragm zipping

actuation

Simulate and test an electrostatically

actuated diaphragm compressor as a

part of a miniature scale refrigeration

system for electronics cooling

• Analytical quasi-static force balance simulation model

• Numerical quasi-static model using FEA

• Analytical dynamic simulation model for fluid damping

• Experimental investigation using custom setup

• Design optimization of diaphragm compressor

• Sathe AA, Groll EA, Garimella SV, 2008, J. Micromechanics and

Microengineering, Vol. 18 # 035010.

• Sathe AA, Groll EA, Garimella SV, 2008, Int. J. Refrigeration (in

review).

Model Validation with

Literature Experiments

Miniature Diaphragm Compressors for Electronics Cooling

Faculty: Eckhard A. Groll and Suresh V. Garimella Students: Abhijit A. Sathe

Objective

ApproachImpact

Selected

Publications

What’s new


To prototype, model, and assess the feasibility of a

free-piston harmonically oscillating linear vapor

compressor for the use in a refrigeration system to

cool consumer electronics.

• Design and build a prototype compressor

• Build load stand to test prototype

• Develop a comprehensive compressor model

• Exercise model and develop design recommendations

• An assessment of the scalability of this style of compressor

• A comprehensive compressor model for use in design

applications of linear compressors

• A fundamental understanding of linear compressors

[1] Trutassanawin et. al, IEEE CPT. 2006.

[2] Hyun et. al, IJR, November 2009.

Prototype Linear Compressor

Miniature Linear Compressors for Electronics CoolingFaculty: E.A. Groll, S.V. Garimella Student: C.R. Bradshaw

Objective

Approach

Selected

Publications

Impact

Compressor

Model


• Significantly enhanced control of flow at the microscale

• High liquid velocities at low voltages

• Noiseless, very low power consumption

• Solutions for chip-level and hot-spot thermal management

V. Bahadur and S. V. Garimella, Langmuir

Vol. 23(9), pp. 4918-4924, 2007.

Bahadur V. and Garimella, S.V., J.

Micromechanics Microengineering,

16:1494-1503, 2006

Patent application filed May 2006,

#60/747,980

Develop technologies enabling

electrical actuation and control of

droplets for providing chip-integrated

thermal management solutions

Droplet resting on top of grooves

Droplet

Droplet resting on top of grooves

Droplet

Droplet wetting grooves

Droplet

Droplet wetting grooves

Droplet

• Electrowetting (electrical control of surface tension) based actuation of electrically conducting droplets

• Electric field-based actuation of dielectric droplets

• Experimental characterization of droplet flow and heat transfer

• Electrically tunable thermal resistance switch through control of droplet states on artificially roughened surfaces

Electrical Actuation of Droplets for Microelectronics Cooling

Faculty: S. V. Garimella Student: Niru Kumari

Objective

Approach

Selected

Publications

Impact


Develop technologies enabling

electrical actuation and control of

droplets for providing chip-integrated

thermal management solutions

V. Bahadur and S. V. Garimella, Langmuir, Vol. 24

(15), 8338–8345, 2008.

N. Kumari, V. Bahadur, and S. V. Garimella, J.

Micromechanics and Microengineering, Vol. 18,

2008.

N. Kumari, V. Bahadur, and S. V. Garimella, J.

Micromechanics and Microengineering, Vol. 18,

2008.

V. Bahadur and S. V. Garimella, Langmuir Vol.

23(9), pp. 4918-4924, 2007.

V. Bahadur and S. V. Garimella, J. Micromechanics

and Microengineering Vol. 16, pp. 1494-1503, 2006.

Significantly enhanced control of flow at the

microscale

High liquid velocities at low voltages

Noiseless, very low power consumption

Solutions for chip-level and hot-spot thermal

management

Electrowetting (electrical control of

surface tension) based actuation of generic

droplets using DC and AC actuation

Experimental characterization of droplet

flow and heat transfer

Electrically tunable thermal resistance

switch through control of droplet states on

artificially roughened surfaces

V

FactE

Droplet

Top plate (continuous electrode)

Bottom plate (electrodes array)

Hydrophobic layer

Dielectric layer

Frequency (kHz)

Ave

rag

eve

locity

(cm

/s)

100

101

102

1030

1

2

3

4

5

6

7

8

2.2 X 10-5

M KCl

10-4

M KCl

10-3

M KCl

Frame 001 03 May 2008

Cassie droplet: 0 V Wenzel droplet: 60 V

Array of electrodes on backside of chip

Futuristic Heat sink

Experimentally obtained droplet velocity

Droplet motion-induced

heat transfer

Electrical Actuation of Droplets for Microelectronics Cooling

Faculty: S. V. Garimella Student: Niru Kumari, Susmita Dash

Objective

Approach

Impact

Selected

Publications


Develop experimentally

validated numerical models

to describe droplet motion

under various actuation

forces.

S. Ravi Annapragada, J.Y. Murthy, S.V.

Garimella, “Experimental Characterization of

Droplet Motion on Inclined Hydrophobic

Surfaces”, 9th ASME-ISHMT Heat and Mass

Transfer Conference, IIT Bombay, India, Jan

4-6, 2010 .

S. Ravi Annapragada, J.Y. Murthy, S.V.

Garimella, “Forces Acting on Sessile Droplets

on Inclined Surfaces”, Summer Heat Transfer

Conference, San Francisco, CA, USA, 2009.

The outcomes of this study

will:

Develop benchmark data for

evaluation of numerical

models for droplet actuation

Predictive numerical models

for droplet motion under

gravitational and electrical

actuation Perform well defined inclined

droplet experiments and

measure contact angles

Develop contact angle

correlations for stationary and

moving droplets

Develop VOF based numerical

methodologies for predicting

droplet actuation and motion

Compare numerical predictions

with data

Develop new numerical models

for the same

Capillary Number, Ca (v/)

Co

nta

ct

An

gle

10-4

10-3

10-2100

105

110

115

120

125

130

adv

rec

Free Body Diagram

Sessile droplet images

Benchmarking of Numerical Model

Moving Droplets

Numerical – Contour plot

Experimental – Outline

Droplet Actuation and Motion Under Various Actuation Forces

Faculty: Jayathi Y. Murthy and S. V. Garimella Student: S. Ravi Annapragada

Objective

Approach

Impact

Selected

Publications

Contact Angle

Correlation


Solar chimney with a plate fin

heat exchanger at the base of

the collector.

Wintertime greenhouse heating can

be achieved by pumping hot

condenser discharge water through

pipes in the floor of the greenhouse.

• Identify and evaluate heat

rejection processes that

provide power plants with

viable alternatives to cooling

towers, lakes, and rivers

• Determine feasibility of

design in regards to cost

requirements, land

requirements, and

environmental factors.

A spray pond using evaporation

and convection to reject heat to

the atmosphere.

Low pressure spray nozzles are

positioned over the pond in an

array.

A shallow, extensive canal

system provides the condenser

discharge water increased

contact with the atmospheric air

allowing it to cool before

reentry to the condenser.

An open water algae bioreactor is

a like a pond with a layer of

Thermophyllic algae growing on

the surface. The algae is

periodically harvested for

biodiesel production.

The pond is heated by the

condenser discharge water up to a

temperature of 75˚C.

Direct Impact:

• Closed loop heat rejection

to the atmosphere

• Electricity production from

plant waste heat in solar

chimney

• Algae bio-fuel production in

algae bioreactor pond

• Winter time greenhouse

heating by process waste heat

• Lower impact on ecosystem

of lakes and rivers

• Less costly than cooling

towers

Broader Impact:

• Alternative methods of heat

rejection not limited to the

power generation industry

• Petroleum refineries, Food

processing plants, Semi-

conductor plants, Chemical

plants, etc.

Alternative Heat Rejection Methods for Power PlantsFaculty: Eckhard Groll and Suresh Garimella Students: R. Leffler and C. Bradshaw

Objective Impact

Methods

Methods Methods


Thermal Ratcheting Prevention of a Molten-Salt Thermocline

• Concentrating Solar Thermal power

plants require thermal storage for times

of reduced insolation

• Thermocline tanks store molten salt at

both excited (hot) and dead (cold)

states in a single tank volume,

separated via buoyancy forces

• A granulated bed of rocks in the tank

reduces the required salt volume but

can induce thermal ratcheting in the

tank wall

• Hoop stresses result from periodic temperature fluctuations in

the steel shell in response to internal molten-salt changes

• Internal insulation dampens influence of molten salt on steel

shell temperatures, reducing thermal ratcheting potential

Student: S. Flueckiger Faculty: Z. Yang, S.V. Garimella

Flueckiger et al., Integrated thermal

and mechanical investigation of

molten-salt thermocline energy

storage, 2011, DOI:

10.1016/j.apenergy.2010.12.31

Figure: Thermocline

temperature and velocity fields

during hot molten-salt

discharge

Thermal Ratcheting Prevention of a Molten-Salt ThermoclineFaculty: Z. Yang, S.V. Garimella Student: S. Flueckiger

Objective Approach

Impact

Selected

Publications

• Detailed CFD investigation of thermocline operation with a

multilayer (internal and external insulation, steel shell) tank wall

design to determine hoop stress in the steel shell

• Parametric study of wall dimensions to minimize hoop stress and

avoid ratcheting


Porous anodic alumina pumps:

Provide multiple nanometer diameter

channels in parallel with long-range order

Reduces applied voltage while maintaining

high electric field

Provides the scaffold for an integrated

screen electrode

Yields high flow rate normalized by

applied voltage and cross-sectional area

Construct a high flow rate, high

back pressure pump that is

scalable for micro to mesoscale

fluid delivery.

Deposit Pt as an electrode on both

sides of the alumina template

Apply electric field across the

alumina channels by probing the

deposited Pt film

Electroosmotic Pumping through Porous Anodic Alumina Templates

Faculty: S. V. Garimella Student: B. D. Iverson

Objective Approach

Impact


Bridgman Growth in a Transparent Material

Faculty: S.V. Garimella Student: J. E. Simpson

Experimental photographs used to

resolve the front locations inside the

ampoule during crystal growth

Predicted thermal and velocity fields

and interface locations for a 40

micrometer growth case

Li, Garimella, Simpson, NHT B, 43,

(1) 117-141, (11) 143-166, 2003.

Simpson, Garimella, Groh, AIAA

JTHT, 16(3), 324-335, 2002.

Selected

Publications

( microscale transport ... · enhancing two-phase heat transfer in microchannel flows. experiments...

Documents