[en] To realize the hyperspectral camouflage under the background of vegetation, a camouflage polyvinyl alcohol coating containing lithium chloride and green pigment particles of chromium sesquioxide (Cr₂O₃) was prepared on a stainless-steel substrate. Based on the four flux Kubelka-Munk model, the reflectances of the coatings with different volume fractions of Cr₂O₃ (f _c) were predicted and compared with those of the membranes without substrate. The results show that when f _c reaches 0.8%, the 0.2 mm thick coating can conceal the reflectance characteristics of the stainless-steel substrate. The reflectances of the coatings with the volume fraction of water (f _w) in the range from 0% to 50% were also calculated via the model. It is found that the reflectances around 1460 nm and 1940 nm decrease with increased f _w due to the significantly enhanced absorption coefficient, and the correlation coefficient between the spectral reflectances of the camouflage coating and an Osmanthus fragrans leaf increases from 0.913 to 0.954, indicating that the coating camouflage performance can be improved by increasing f _w. (paper)

[en] Highlights: • A solar reactor coupled with sodium heat pipe was tested with a solar simulator. • The radiative power of the high flux solar simulator was measured and calibrated. • The solar thermal conversion efficiency of the reactor can achieve 90%. • The solar reactor has shown good heat absorbing and transfer abilities. -- Abstract: Solar thermochemical reactor is the key to store solar energy as chemical basic fuels through high temperature chemical reactions. The thermal performance of a solar high temperature thermochemical reactor coupling heat pipe technology has been preliminary performed under a high-flux solar simulator. The radiative power of the solar simulator was measured and calibrated with an infrared camera and an optical meter. The measurement indicates an average heat flux exceeding 130 kW/m² over a 210-mm-diameter focal plane. The temperature characteristics and thermal performance of the reactor with only nitrogen cooling were investigated under various nitrogen flow rates and heat flux inputs. It is showed that the input heat flux has effect on the reactor temperature and the temperature distribution on heating surface is associated with the radiative flux distribution from the solar simulator. The heating surface temperature is at the range of 850–1075 K for the input heat flux of 55.5–108.8 kW/m² and cooling gas flow rate less than 33 m³/h. The gas out temperature obtained is lower than 700 K with room temperature inlet. The radiation heat loss through heating surface accounts for 45–60% of the radiative power incident on the reactor. The thermal efficiency of STPCR is greatly influenced by cooling gas flow rate and it is in the range of 27–90% with cooling gas flow rate from 5 m³/h to 33 m³/h. Whereas the thermal efficiency appears less influenced by heat flux inputs. Good heat absorbing and transfer abilities of the reactor has been shown.