404
J. Eur. Opt. Society-Rapid Publ. 22, 41( 2026)
Figure
2.( a) Description of different parts of reflection on a surface,( b) comparison of HDR( Hemispherical Directional Reflectivity) and DDR( Diffuse Hemispherical Directional Reflectivity) measurement in an Ulbricht Sphere of cured white and black powder coating and Alanod sheet. HDR and DDR are identical for the two coatings indicating a Lambertian scatter whereas the two are quite different for the high specular Alanod.
Table 1. Results for maximum / minimum values of simulated irradiance and measured temperature of the white and black sample( Values in the holes are excluded).
Max irradiance
Min irradiance
Ratio max / min
Max temperature
Min temperature
|
|
Simulated values |
|
|
Measured values |
|
White sample |
3200 W / m 2 |
2300 W / m 2 |
1.39 |
152 ° C |
115 ° C |
1.32 |
Black sample |
7500 W / m 2 |
4500 W / m 2 |
1.67 |
266 ° C |
190 ° C |
1.40 |
Ratio max / min
Figure
3. Simulation( b) and heating results( a) for the black sample. The ratio of temperatures matches the ratio of irradiances at the main surfaces of the sample. The red color corresponds here to higher temperatures while yellow / green resembles lower temperatures.
Figure 4. Detailed results of simulation and infrared camera show differences due to heat flow inside the sample. The side wall in the IR-picture( a) shows a heat sink at the bottom: heat flow to Alanod sheets. The pure ray trace simulation( b) does not show a lower irradiance at the bottom of the side surface.