MicroStructured Heat Exchangers

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Micro-Structured Heat Exchangers Reactors for
ISRU A. McCandless1, S. Motakef2, D. Guidry1,
and M. Overholt2 1International Mezzo
Technologies, Inc. 2Cape Simulations,
Inc. November 2, 2004
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New Enabling Technology

• High performance micro-machined thermo-chemical
  devices for energy conversion and In-Situ
  Resource Utilization
• Heat Exchangers
• Reactors

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Core Technology

• Micro-manufacturing
• devices with micro-scale features (10s of
  microns) over macro-scale dimensions of (1-100
  cm)

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Micro-Channel Thermo-Chemical Devices

• Applications for Moon Mars Missions
• Propellant production
• Fuel cell reagant production
• Human habitat power life support systems

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High Temp. Processes
Lunar
Mars
Source R.S. Baird
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Micro-Channel Thermo-Chemical Devices

• Heat Exchangers
• Micro-structured surfaces
• ?lower diffusive thermal resistances
• ?Higher performance per weight volume

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Micro-Channel Thermo-Chemical Devices

• Reactors
• Reduced resistance to mass transfer
• Intimate thermal exchange between catalytic
  reactor and heat exchanger
• Intimate thermal coupling of endo- and
  exo-thermic reactions
• Accurate control of reaction temperature
• Non-Equilibrium chemical products

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Micro-channels in Cross Flow Heat Exchangers
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Cross Flow Gas-Liquid Heat Exchangers
Liquid Inlet
Gas Flow
Heat Exchange Panel
Liquid Outlet
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Comparison with Existing Technology
Heat Transfer Per Unit of Frontal Area
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Heat Transfer Per Unit Volume
Comparison with Existing Technology
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Comparison with Existing Technology
Pressure Per Unit Frontal Area
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Comparison with Existing Technology
Compact Plate Fin Heat Exchanger
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Comparison with Existing Technology

• Comparison with a truck radiator the same heat
  transfer per frontal area, but much higher
  performance per volume mass.

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Example of Packaged HX
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Corrugated Heat Exchangers Yield Ultra Low
Frontal Area
Heat exchanger can be inside the duct!
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LIGA Process
Molding
Lithography
Post Machining
Electroplating
Metalization
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Advantages of LIGA

• Tall/deep structures up to 3 mm/high aspect
  ratios up to 100
• Vertical sidewalls 1um/1000 um slope
• Smooth sidewalls less than 30 nm variations
• Lateral dimensional control better than 1 um
• Materials Metal, Ceramic, Polymer
• Low per-unit manufacturing cost

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Additional Types of Heat Exchangers

• Gas Gas
• Liquid Liquid
• Vapor Gas
• Vapor Liquid

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Micro Jet Cooling Array
Systems for removal of very high heat fluxes


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Micro Jet Cooling Array

• Single phase impingement cooling
• gt100 impinging microjets/cm2
• Very high heat transfer coefficients
• Easily removes 1kW/cm2 of heat

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4-kWatt Cold Plate
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Ceramic Micro-channel Devices

• Applications
• High Temperature Heat Exchangers
• High Temperature Reactors
• Recuperators

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Ceramic Micro-channel Devices

• Advantages
• Can go up to very high temperatures
• Hospitable to a wide range of catalysts
• Challenges
• Creation of high aspect ratio structures
• Ceramic-Ceramic bonding

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Ceramic Micro-channel Devices
500 mm x 1.5 mm structures in sintered SiN
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Ceramic Micro-channel Devices

• Bonding of Ceramic Plates
• Strong ceramic-ceramic bonds created
• (Please see me for samples)
• Mechanical tests to be conducted shortly

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Ceramic Micro-channel Devices

• Building Block
• Micro-machined ceramic panel

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Ceramic Micro-channel Devices
Individual ceramic plates, aligned, pressed
together, then sintered
Fins Length 1.5-2.5 mm Width at base 300
mm Width at tip 200 mm Gap Between Fins 300-400
mm
Counterflow fluids in alternating layers very
effectively coupled via fins
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Ceramic Micro-channel Devices
Examples of Ceramic Heat Exchangers Reactors

• Counter Flow

Cross Flow
Dogbone
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Ceramic Micro-channel Devices

• Gas Turbine Recuperator for UMAV
• 81 effectiveness
• 30 kW capacity
• Weight 2lbs
• Volume 6 x 2 x 6

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Additional Manufacturing Technologies

• Surface Micromachining
• Tradition and Micro Electro Discharge Machining
  (EDM)
• Sinker
• Wire
• UV Lithography
• Etching
• Laser Drilling, Cutting, and Welding

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Collaborators
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Collaborations

• We are looking for opportunities to collaborate
  on design, modeling, fabrication, and testing of
  heat exchangers and reactors.

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Micro-Channel Thermo-Chemical Devices

• Thank You!