heat conduction in porous absorption layers for thermography applications · 2014-11-19 · thin...
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![Page 1: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/1.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Heat Conduction in Porous Absorption Layers for Thermography Applications
Lars Helmich and Andreas Hütten
![Page 2: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/2.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Outline
• Magnetocaloric Effect
• Magnetic Shape Memory Alloys
Ø Experimental preparation
Ø Why do we actually need an absorption layer?
• Simulation
Ø Comparison of two different absorption materials
![Page 3: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/3.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Introduction
• Conventional Magnetocaloric effect
![Page 4: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/4.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Experimental preparation
MgO(001) substrate
Vanadium (35 nm) SMA (200 nm)
Sample holder with a hole
• Sputter deposition • Selective wet-chemical etching of Vanadium • Transfer of the sample to a special sample holder
2nd step 1st step
![Page 5: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/5.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Absorption layer
• Two types of absorption layers • Commercially available carbon laquer • Custom developed „gold black“
Ø Do these absorption layers influence the observed SMA‘s surface temperature?
![Page 6: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/6.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Absorption layer
Absorption layer
SMA sample
Sample holder
Backside view
![Page 7: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/7.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Absorption layer
SEM Image of Gold black „Gold black“ on glass
![Page 8: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/8.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Simulation
• Heat transfer in porous media
• Input parameters are determined experimentally • Layer thickness: 3µm (AFM) • Volume fraction: 0.05 (SEM) • Thermal conductivity and heat capacity: bulk values
keq = ✓pkp + (1� ✓p)k
(⇢cp)eq@T
@t+ ⇢cp~u · ~rT = ~r · (keq~rT ) +Q
(⇢cp)eq = ✓p⇢pcp,p + (1� ✓p)⇢cp
![Page 9: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/9.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Simulation
• Flat structure (5 mm lateral, 3 µm thickness) • Automated meshing routines fail Ø Swept mesh
Boundary conditions • Inward heat flux • Surface to ambient radiation • Constant temperature
swept mesh
![Page 10: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/10.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Results
Commercially available carbon black • Heat pulse: 1K • Surface temperature change: 0.01K • Cannot be detected
![Page 11: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/11.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Results: Gold blacks
• Parametric sweep for different heat pulses Ø Linear relation Ø Gold black is an appropriate choice as absorber material Ø Result can be used for calibration of IR sensor
Surface temperature profile for Gold blacks
Heat pulse from SMA (green) results in a temperature change on the absorber surface (blue)
![Page 12: Heat Conduction in Porous Absorption Layers for Thermography Applications · 2014-11-19 · Thin Films and Physics of Nanostructures Lars Helmich September 18th, 2014 Heat Conduction](https://reader033.vdocuments.us/reader033/viewer/2022042020/5e771e199b5f7a7adb49f801/html5/thumbnails/12.jpg)
Thin Films and Physics of Nanostructures
Lars Helmich September 18th, 2014
Conclusion
• Gold black absorption layers can be fabricated by thermal evaporation
• Heat transfer in porous media • Commercially available carbon black is inappropriate for thin films
• Gold blacks are a proper choice for thin SMA samples
Funding by Deutsche Forschungsgemeinschaft (DFG) in the scope of project A6 within SPP 1599 is gratefully acknowledged