Advanced Cooling Systems

Advanced Cooling Systems

© 2008 ANSYS, Inc. All rights reserved.

1

ANSYS, Inc. Proprietary

Spray Cooling of a Hot Surface with Water Droplets • Droplets Colored by Diameter (splashing) • Surface Colored by Temperature • Planar Cut Shows Concentration of Water Vapor

• • • • •

Spray Angle Flow Rate Droplet Size Initial Droplet Speed Droplet Material and Properties

© 2008 ANSYS, Inc. All rights reserved.

2

ANSYS, Inc. Proprietary

Micro Channels • Very Small Hydraulic Diameters ~ 100 m • Very High Heat Transfer Coefficient (10,000 < h < 100,000 w/m2K) • But Very High Pressure Drop!

parallel flow counter flow

© 2008 ANSYS, Inc. All rights reserved.

3

ANSYS, Inc. Proprietary

Heat Pipes

• Passive Device of Very High “Effective” Thermal Conductivity • Heat is Transferred By: – Evaporation (evaporator section) – Convection (adiabatic section) – Condensation (condenser)

liquid vapor

evaporator © 2008 ANSYS, Inc. All rights reserved.

adiabatic 4

condenser ANSYS, Inc. Proprietary

Heat Pipes Case Study

liquid flow

vapor flow

Pressure

Temperature

Vadakkan et al. “Transient Analysis of flat heat pipes”, SHTC, HT2003-47349

© 2008 ANSYS, Inc. All rights reserved.

5

ANSYS, Inc. Proprietary

Multiphysics Cooling Systems

© 2008 ANSYS, Inc. All rights reserved.

6

ANSYS, Inc. Proprietary

Piezoelectric Fan • Piezoelectric Fan – Spot cooling for electronic components – Low magnetic permeability – Blade driven by piezoelectric bimorph Bimorph

Blade

FR4 Board Two piezoelectric layers with opposing polarity

Finite Element Mesh © 2008 ANSYS, Inc. All rights reserved.

7

ANSYS, Inc. Proprietary

Piezoelectric Fan

• Results – Fan Driven at Resonance – 115Volts at 60 Hz Fixed

© 2008 ANSYS, Inc. All rights reserved.

+Vin

8

ANSYS, Inc. Proprietary

Thermoelectric Cooler • Multistage Thermoelectric Cooler – Thermal-electric coupling • n-type and p-type semiconductors Cold Side (Heat Absorbed)

Ground

20 Amps

Hot Side (Heat Rejected)

© 2008 ANSYS, Inc. All rights reserved.

9

ANSYS, Inc. Proprietary

Thermoelectric Cooler • Thermoelectric Results – Thermal gradient in Peltier blocks

Electric Potential

Cold Side (Heat Absorbed)

Hot Side (Heat Rejected) Temperature © 2008 ANSYS, Inc. All rights reserved.

Current Density

10

ANSYS, Inc. Proprietary

Thermoelectric Cooler • Optimization – Response surface and sensitivity

© 2008 ANSYS, Inc. All rights reserved.

11

ANSYS, Inc. Proprietary