scholarly journals Multispectral camouflage for infrared, visible, lasers and microwave with radiative cooling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huanzheng Zhu ◽  
Qiang Li ◽  
Chenning Tao ◽  
Yu Hong ◽  
Ziquan Xu ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Input Power ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Long Wavelength ◽  
Military Equipment ◽  
Atmospheric Window ◽  
Visible Lasers ◽  
Ir Bands ◽  
Low Emittance

AbstractInterminable surveillance and reconnaissance through various sophisticated multispectral detectors present threats to military equipment and manpower. However, a combination of detectors operating in different wavelength bands (from hundreds of nanometers to centimeters) and based on different principles raises challenges to the conventional single-band camouflage devices. In this paper, multispectral camouflage is demonstrated for the visible, mid-infrared (MIR, 3–5 and 8–14 μm), lasers (1.55 and 10.6 μm) and microwave (8–12 GHz) bands with simultaneous efficient radiative cooling in the non-atmospheric window (5–8 μm). The device for multispectral camouflage consists of a ZnS/Ge multilayer for wavelength selective emission and a Cu-ITO-Cu metasurface for microwave absorption. In comparison with conventional broadband low emittance material (Cr), the IR camouflage performance of this device manifests 8.4/5.9 °C reduction of inner/surface temperature, and 53.4/13.0% IR signal decrease in mid/long wavelength IR bands, at 2500 W ∙ m−2 input power density. Furthermore, we reveal that the natural convection in the atmosphere can be enhanced by radiation in the non-atmospheric window, which increases the total cooling power from 136 W ∙ m−2 to 252 W ∙ m−2 at 150 °C surface temperature. This work may introduce the opportunities for multispectral manipulation, infrared signal processing, thermal management, and energy-efficient applications.

scholarly journals Multispectral camouflage for infrared, visible, lasers and microwave with radiative cooling

2020 ◽  
Author(s):  
Huanzheng Zhu ◽  
Qiang Li ◽  
Chenning Tao ◽  
Yu Hong ◽  
Ziquan Xu ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Input Power ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Long Wavelength ◽  
Military Equipment ◽  
Atmospheric Window ◽  
Visible Lasers ◽  
Ir Bands ◽  
Low Emittance

Abstract Interminable surveillance and reconnaissance through various sophisticated multispectral detectors present threats to military equipment and manpower. However, a combination of detectors operating in different wavelength bands (from hundreds of nanometers to centimeters) and based on different principles raises challenges to the conventional single-band camouflage devices. In this paper, multispectral camouflage is demonstrated for the visible, mid-infrared (MIR, 3-5 and 8-14 μm), lasers (1.55 and 10.6 μm) and microwave (8-12 GHz) bands with simultaneous efficient radiative cooling in the non-atmospheric window (5-8 μm). The device for multispectral camouflage consists of ZnS/Ge multilayer for wavelength selective emission and Cu-ITO-Cu metasurface for microwave absorption. In comparison with conventional broadband low emittance material (Cr), the IR camouflage performance of this device manifests 8.4/5.9 °C reduction of inner/surface temperature, and 53.4/13.0 % IR signal decrease in mid/long wavelength IR bands, at 2500 W∙m-2 input power density. Furthermore, we revealed that the natural convection in the atmosphere can be enhanced by radiation in the non-atmospheric window, which increases the total cooling power from 136 W∙m-2 to 252 W∙m-2 at 150 °C surface temperature. This work may introduce the opportunities for multispectral manipulation, infrared signal processing, thermal management, and energy-efficient applications.

scholarly journals Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Mingke Hu ◽  
Gang Pei ◽  
Lei Li ◽  
Renchun Zheng ◽  
Junfei Li ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Heating Surface ◽  
Solar Heating ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Relative Temperature ◽  
Composite Surface ◽  
Spectral Selectivity ◽  
Atmospheric Window ◽  
Inclination Angles

A spectral selectivity surface for both solar heating and radiative cooling was proposed. It has a high spectral absorptivity (emissivity) in the solar radiation band and atmospheric window band (i.e., 0.2~3 μm and 8~13 μm), as well as a low absorptivity (emissivity) in other bands aside from the solar radiation and atmospheric window wavelengths (i.e., 3~8 μm or above 13 μm). A type of composite surface sample was trial-manufactured combining titanium-based solar selective absorbing coating with polyethylene terephthalate (TPET). Sample tests showed that the TPET composite surface has clear spectral selectivity in the spectra of solar heating and radiation cooling wavelengths. The equilibrium temperatures of the TPET surface under different sky conditions or different inclination angles of surface were tested at both day and night. Numerical analysis and comparisons among the TPET composite surface and three other typical surfaces were also performed. These comparisons indicated that the TPET composite surface had a relative heat efficiency of 76.8% of that of the conventional solar heating surface and a relative temperature difference of 75.0% of that of the conventional radiative cooling surface, with little difference in cooling power.

scholarly journals Simple PDMS/AIN emitter as a passive daytime radiative cooling design

2021 ◽  
Author(s):  
Mabchour ◽  
benlattar mourad
Keyword(s):  
Outer Space ◽  
Solar Spectrum ◽  
Ambient Air ◽  
Heat Radiation ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Spectral Selectivity ◽  
Solar Energy Harvesting ◽  
Atmospheric Window ◽  
Cooling Design

Abstract Radiative cooling is a passive cooling purpose where a surface naturally cools by radiating the mid-infrared heat radiation to the cold outer space through the atmospheric window . Daytime passive radiative cooling technologies can be simply provided by using a multi-layer design that emits strongly in the transparency atmospheric window, while presents high reflectance in the solar spectrum . In this study, we propose a polydimethylsiloxane foil ) coated aluminum nitride (AIN) deposed onto silver (Ag) coated glass as a radiative cooler for enhancing both daytime and nighttime radiative cooling performances. The spectral selectivity of the proposed device was obtained using matrix method. Numerical results show that our proposed design can reflect more than 96 % in the solar spectrum, while its average emissivity in the atmospheric window can reach more than 90 %.In the absence of wind speed, the proposed device can achieve a net cooling power of under direct sunlight, cooling to a below the ambient air temperature. At nighttime, the proposed device temperature can drop by below the ambient, leading to a net cooling power of . Therefore, the proposed radiative design can fundamentally enable new methods for exploiting solar energy harvesting and energy conservation.

scholarly journals Performance simulation of polymer-based nanoparticle and void dispersed photonic structures for radiative cooling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jay Prakash Bijarniya ◽  
Jahar Sarkar ◽  
Pralay Maiti
Keyword(s):  
Fdtd Method ◽  
Solar Spectrum ◽  
Thermal Infrared ◽  
Performance Estimation ◽  
Radiative Cooling ◽  
Slab Thickness ◽  
Slight Variation ◽  
Performance Simulation ◽  
Atmospheric Window ◽  
Substrate Independent

AbstractPassive radiative cooling is an emerging field and needs further development of material. Hence, the computational approach needs to establish for effective metamaterial design before fabrication. The finite difference time domain (FDTD) method is a promising numerical strategy to study electromagnetic interaction with the material. Here, we simulate using the FDTD method and report the behavior of various nanoparticles (SiO2, TiO2, Si3N4) and void dispersed polymers for the solar and thermal infrared spectrums. We propose the algorithm to simulate the surface emissive properties of various material nanostructures in both solar and thermal infrared spectrums, followed by cooling performance estimation. It is indeed found out that staggered and randomly distributed nanoparticle reflects efficiently in the solar radiation spectrum, become highly reflective for thin slab and emits efficiently in the atmospheric window (8–13 µm) over the parallel arrangement with slight variation. Higher slab thickness and concentration yield better reflectivity in the solar spectrum. SiO2-nanopores in a polymer, Si3N4 and TiO2 with/without voids in polymer efficiently achieve above 97% reflection in the solar spectrum and exhibits substrate independent radiative cooling properties. SiO2 and polymer combination alone is unable to reflect as desired in the solar spectrum and need a highly reflective substrate like silver.

Bio-skin inspired 3D porous cellulose/AlPO4 nano-laminated film with structure-enhanced selective emission for all-day non-power cooling

2021 ◽  
Author(s):  
Shuangjiang Feng ◽  
Yuming Zhou ◽  
Xi Chen ◽  
Shengnan Shi ◽  
Chenghuan Liu ◽  
...  
Keyword(s):  
Radiative Cooling ◽  
Preparation Technology ◽  
Cellulose Films ◽  
Highly Efficient ◽  
Atmospheric Window ◽  
Complex Preparation

Porous cellulose films have been reported as sustainable and highly-efficient non-power radiative cooling (PRC) materials but still challenged by their insufficient atmospheric window (AM) emissivity and complex preparation technology. Herein,...

Combustor Wall Surface Temperature and Heat Flux Measurement Using a Fiber-Coupled Long Wave Infrared Hyperspectral Sensor

2021 ◽  
Author(s):  
Aravind Chandh ◽  
Oleksandr Bibik ◽  
Subodh Adhikari ◽  
David Wu ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Flux Measurement ◽  
Heat Fluxes ◽  
Long Wavelength ◽  
Combustion Gases ◽  
Acoustic Perturbation ◽  
Accuracy And Precision ◽  
Long Wavelength Infrared

Abstract In this paper, we discuss the development of a non-intrusive surface temperature sensor based on long-wavelength infrared (LWIR) hyperspectral technology. The LWIR detection enables to minimize optical interferences from hot combustion gases (emission mostly within UV-MWIR region). Utilization of hyperspectral detection allows to further improve temperature measurement accuracy and precision. The developed sensor with fiber coupling provides the required flexibility to be maneuvered around/through combustor hardware. The LWIR fiber probe is fully protected by the custom-designed water-cooled probe housing. This device is designed to sustain temperature of 2400 K at pressure of 50 bar, which enables long-term optical diagnostics inside the practical high-pressure combustion facilities where extreme thermal acoustic perturbation and intense heat fluxes are present. The housing featured a diamond window to selectively measure spectra in the LWIR region to get accurate surface temperature exclusively of the combustor wall. The probe was installed into a RQL style combustor to get surface temperature of both hot and cold side of the combustor wall. Further, pointwise heat flux estimates across the combustion liner wall was derived using the temperature measurements.

scholarly journals Analysis of Sustainable Materials for Radiative Cooling Potential of Building Surfaces

2018 ◽  
Vol 10 (9) ◽  
pp. 3049 ◽  
Author(s):  
Roxana Family ◽  
M. Mengüç
Keyword(s):  
Heat Transfer ◽  
Emission Spectra ◽  
Spectral Emissivity ◽  
Volumetric Analysis ◽  
Solar Heating ◽  
Heat Transfer Analysis ◽  
Surface Phenomenon ◽  
Radiative Cooling ◽  
Atmospheric Window ◽  
Building Surfaces

The main goal of this paper is to explore the radiative cooling and solar heating potential of several materials for the built environment, based on their spectrally-selective properties. A material for solar heating, should have high spectral emissivity/absorptivity in the solar radiation band (within the wavelength range of 0.2–2 μm), and low emissivity/absorptivity at longer wavelengths. Radiative cooling applications require high spectral emissivity/absorptivity, within the atmospheric window band (8–13 μm), and a low emissivity/absorptivity in other bands. UV-Vis spectrophotometer and FTIR spectroscopy, are used to measure, the spectral absorption/emission spectra of six different types of materials. To evaluate the radiative cooling potential of the samples, the power of cooling is calculated. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis is used. Results are discussed for the selection of the best materials, for different applications on building surfaces.

scholarly journals The Application of Passive Radiative Cooling in Greenhouses

2019 ◽  
Vol 11 (23) ◽  
pp. 6703 ◽  
Author(s):  
Chia-Hsin Liu ◽  
Chyung Ay ◽  
Chun-Yu Tsai ◽  
Maw-Tien Lee
Keyword(s):  
Convection Heat Transfer ◽  
Cooling Power ◽  
Radiative Cooling ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Monolayer Film ◽  
Cooling Method ◽  
The World ◽  
Oxide Particles ◽  
Reducing Energy

At present, greenhouses are used to grow a variety of crops around the world. However, with the change of climate, the increasingly harsh weather makes it more and more disadvantageous for people to work inside, and plants are difficult to grow. Previous research has illustrated that radiative cooling can be realized by using certain nonmetal oxide particles created for emission in an infrared atmospheric transparency window, which is an environmentally friendly cooling method due to reducing energy consumption. Polyethylene (PE)-based formulations with a UV stabilizer and nonmetal oxide particles (NOP) were first granulated and then formed a monolayer film by co-injection molding. The experimental results show that due to passive radiative cooling, under the environmental conditions of 35 °C, and only considering the natural convection heat transfer, the net cooling power of the greenhouse film developed in this study is 28 W·m−2 higher than that of the conventional PE film. The temperature inside the simulated greenhouse cladded with the new greenhouse covering was on average 2.2 °C less than that of the greenhouse with the conventional PE film.

Characteristics for evaluating the reactor regime with endothermic reversible reaction

1987 ◽  
Vol 52 (4) ◽  
pp. 929-938
Author(s):  
Josef Horák ◽  
Zina Valášková
Keyword(s):  
Surface Temperature ◽  
Steam Reforming ◽  
Catalyst Activity ◽  
Combustion Products ◽  
Input Power ◽  
Reversible Reaction ◽  
Reactor Radiation ◽  
Points Of View ◽  
Selection Of ◽  
Simplified Mathematical Model

Criteria are proposed in the paper for evaluating the reactor regime (with endothermic reversible reaction, heated by radiation of combustion products) from thermodynamic and kinetic points of view. The limiting reactor regimes in which the controlling process is the process kinetics or the heat transfer are defined. The effect of the catalyst activity on the reactor output and the surface temperature of the reaction tube and the effect of heat input power of the reactor radiation section on the conversion and the surface temperature of the tube are discussed. The results are verified on a simplified mathematical model of steam reforming and employed to discuss the selection of the regime of an industrial reactor.

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