Test method for solar radiation absorption coeffic

The test method of solar radiation absorption coefficient of temperature controlled paint has achieved greater combustion efficiency improvement effect

Test Method of solar radiation absorption coefficient of temperature controlled paint

December 7, 2018

1 preface

paint products mainly check the performance of the film formed on the object as a material, mainly by physical methods, supplemented by chemical methods. Coatings for special purposes should be tested for their special properties. Temperature control paint is a special kind of paint, which is often used as the surface material of spacecraft. Recently, it is also used in various industrial buildings with strict requirements for temperature control. China's paint exports to developed countries are mainly in the middle and low end. Temperature control coating is a light scattering material. With the help of the diffuse reflection of fine dispersed pigments in the coating on sunlight and the radiation characteristics of the coating on the infrared band, the absorption and radiation ratio of the coating can be adjusted. The protection of the host is not introduced here to achieve the purpose of temperature control. The so-called absorption radiation ratio refers to the absorption coefficient of solar radiation absorbed by substances α Its thermal emission coefficient ε Ratio of α/ε， Generally speaking, the surface temperature T of the coating is directly proportional to the absorption and radiation ratio of the coating, as shown in the following formula:

Where, α： Solar radiation absorption coefficient; ρ m: Reflectivity value of coating (%); E: Solar irradiance, w/m2. According to Nim spectral reflectance calibration method, the diffuse reflectance calibration test was carried out on the samples

2 experimental principle

the method of measuring absolute diffuse reflectance with auxiliary integrating sphere is often called double sphere method or auxiliary sphere method. The measurement principle is shown in Figure 1

in Figure 1, 1A shows that the auxiliary integrating sphere is used as the sample for measurement, and figure 1b shows that the effective reflectance of the auxiliary integrating sphere is measured according to the integrating sphere theory ρ S is:

main measuring instruments

main measuring instruments used in the experiment and their technical indicators are shown in Table 1

in addition, the indoor calibration test conditions also meet: spectral measurement range: (300 ~ 2300) NM; Wavelength accuracy: 1nm; Spectral bandwidth: 4nm; Measuring geometric condition: 0/d; Temperature: 23 ℃ ± 2 ℃; Relative humidity: 50% ± 5%

4 spectra and data

typical experimental spectra are shown in Figure 2 (a) ～ (d)

it can be seen from the above four spectra that different chemical methods were used to control the surface temperature of various temperature control coatings tested in the experiment

the four coatings in Figure 2 (a) focus on improving the reflectance of samples in the visible region

Figure 2 (b) is to comprehensively improve the reflectance of the sample in the ultraviolet, visible and near-infrared regions

the characteristics of each sample in Fig. 2 (c) and Fig. 2 (d) are different. Curve 11 can be classified into the classification of Fig. 2. The difference is that the reflectance of the visible region of curve 11 is lower than that of the near-infrared region; The reflectance of curve 15 in the visible region increases rapidly. From the calculation of solar radiation absorption coefficient α It can be seen from the weight coefficient curve of (see Figure 3): the transmittance curve of the coating accounts for a high proportion of the weight coefficient of Mn in the visible region (380 ~ 780), which plays a great role in improving the surface characteristics of the coating. The focus should be on the spectral characteristics of the visible region. Such technology is used in all curves in figure

2 (a); The rest of the curves have some errors in the formula materials. Calculate the solar radiation absorption coefficient of each curve in the above figure α， Such as table 2 with large volume

4 outdoor temperature rise test data

in view of the difference in weather, the uncertainty of outdoor test is large. The results of three tests are shown in Figure 4, and series 1, 2 and 3 represent three tests respectively. Considering the difference of functional components used in various coatings and the influence of test uncertainty, this conclusion is basically reached: solar radiation absorption coefficient α The larger the temperature, the higher the temperature rise; Solar radiation absorption coefficient α The smaller, the lower the temperature rise

solar radiation absorption coefficient α Compared with the temperature rise test, it can be seen that the solar radiation absorption coefficient of various coatings is simple and reliable α The test can relatively evaluate the outdoor temperature rise effect of paint, so as to guide the specific use of various industries