Test method for solar radiation absorption coefficient of temperature-controlled coatings

1 Foreword
coating products are mainly to check how well it is formed as a material on an object, mainly by physical methods and supplemented by chemical methods. Special-purpose coatings should be tested for their special properties. Temperature-controlled coatings are a special kind of coating, which is often used as surface material on spacecraft, and recently also used in various industrial buildings
China
. Temperature-controlled coating is a kind of light scattering material, with the help of finely dispersed pigments in the coating for the diffuse effect of sunlight and the radiation characteristics of the coating for the infrared band, adjust the absorption radiation ratio of the coating coating, to achieve the purpose of temperature control. The so-called absorption radiation ratio refers to the absorption coefficient of solar radiation α to its thermal emission coefficient ε α /ε, in general, the surface temperature of the coating is directly compared to the absorption radiation ratio of the coating, as follows:
, α ρm: solar radiation absorption coefficient; The diffuse ratio calibration test was performed on the sample according to the NIM-06-16-2003 spectral reflection ratio calibration method.
2 experimental principle
method of measuring absolute diffuse ratio by auxiliary integral ball is often referred to as double ball method or auxiliary ball method. The measurement principle is shown in Figure 1.
Figure 1a indicates that the auxiliary integral ball is measured as a sample, Figure 1b indicates the measurement of the sample under test ρs, according to the integration ball theory, the effective reflection ratio of the auxiliary integral ball is:
main measuring instrument
the main measuring instrument used in the experiment process of the main measuring instrument and its technical indicators see Table 1
Spectral bandwidth: 4nm; measurement geometry: 0/d; temperature: 23C±2C; relative humidity: 50% ±5%.
4 spectra and
typical experimental spectra are shown in Figure 2 (a) to (d).
can be seen from the above 4 spectral maps: the various temperature-controlled coatings measured in the experiment, respectively, using different chemical methods to control the surface temperature of the coating.
4 coatings in Figure 2 (a) focus on improving the sample reflection ratio in the visible area;
Figure 2 (b) is a comprehensive improvement of the reflection ratio of the sample in the ultraviolet
, visible and near-infrared zone; From the calculation of the solar radiation absorption coefficient α weight coefficient graph can be seen (see Figure 3): the paint transmission ratio curve in the visible area (380 to 780) mn weight coefficient accounted for a higher proportion of the role of large, improve the surface characteristics of the coating, the focus should be placed on the spectral characteristics of the visible area, Figure
2 (a) in each curve is used in this technique; Calculate the solar radiation absorption coefficients for each curve in the figure above, α table 2.
4 Outdoor temperature rise experimental data
in view of the differences in weather, outdoor test uncertainty is greater, 3 test results shown in Figure 4, series 1, 2 and 3 represent 3 tests. Taking into account the differences in functional parts used in various coatings and the effects of the test uncertainty, it is basically concluded that the solar radiation absorption coefficient is α the higher the temperature rise α
So solar radiation absorption coefficient α and temperature rise test comparison
it can be seen that a variety of coatings for simple, reliable solar radiation absorption coefficient α test, can be relatively evaluated outside the coating temperature rise effect, so as to guide the specific use of various industries.