advanced cooling systems - s3. · pdf file© 2008 ansys, inc. all rights reserved. 1...
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© 2008 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
Advanced Cooling Systems
© 2008 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
Spray Cooling of a Hot Surface
with Water Droplets
• Spray Angle
• Flow Rate
• Droplet Size
• Initial Droplet Speed
• Droplet Material and Properties
• Droplets Colored by Diameter
(splashing)
• Surface Colored by Temperature
• Planar Cut Shows Concentration
of Water Vapor
© 2008 ANSYS, Inc. All rights reserved. 3 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. 4 ANSYS, Inc. Proprietary
Heat Pipes
evaporator adiabatic condenser
vaporliquid
• Passive Device of Very High “Effective” Thermal Conductivity
• Heat is Transferred By:
– Evaporation (evaporator section)
– Convection (adiabatic section)
– Condensation (condenser)
© 2008 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary
Heat Pipes Case Study
Temperature Pressure
liquid flow
vapor
flow
Vadakkan et al. “Transient Analysis of flat heat pipes”, SHTC, HT2003-47349
© 2008 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary
Multiphysics
Cooling Systems
© 2008 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary
Piezoelectric Fan
• Piezoelectric Fan
– Spot cooling for electronic components
– Low magnetic permeability
– Blade driven by piezoelectric bimorph
Blade
Bimorph
FR4 Board
Finite Element Mesh
Two piezoelectric
layers with opposing
polarity
© 2008 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary
Piezoelectric Fan
• Results
– Fan Driven at Resonance
– 115Volts at 60 Hz
+VinFixed
© 2008 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary
Thermoelectric Cooler
• Multistage Thermoelectric Cooler
– Thermal-electric coupling
• n-type and p-type semiconductors
20 Amps
Ground
Cold Side
(Heat Absorbed)
Hot Side (Heat Rejected)
© 2008 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary
Thermoelectric Cooler
• Thermoelectric Results
– Thermal gradient in Peltier blocks
Hot Side (Heat Rejected)
Cold Side (Heat Absorbed)
Temperature
Electric
Potential
Current
Density
© 2008 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary
Thermoelectric Cooler
• Optimization
– Response surface and sensitivity