This work deals with the characterization of biochar deposited on a thin metallic sheet, used to enhance the evaporation in heat exchangers. The effectiveness of such deposit is done by means of the heated thin foil thermographic technique. The thermal diffusivity of the foil is the main objective of this study. In the proposed method, a pulse of 2 ms duration is produced by a laser, and periodically projected on the surface of an opaque sample of which the thermal parameters have been determined by classical measurements. The spatial distribution of the laser light pattern is random, after passing through a mask like a QR code. Several masks with different spatial features and distribution were prepared by sputtering thin layer (100 nm) of gold on a piece of glass covered by a pattern. Using the masks, samples were photothermally excited by impulsive laser light patterns. The resulting dynamic temperature field evolution at the sample surface was observed by a fast IR camera in the LW, and the thermal diffusion process was recorded by a sequence of IR images. In this contribution, a theoretical model is described and utilized to analyze the spatiotemporal dependence of the temperature field.
Relation between evaporation rate and temperature change due to latent heat is investigated with thermal imaging in micro scale and a numerical simulation. Evaporation involves many complicated phenomena, in addition to vapor diffusion in the air. The surface of droplet is cooled during evaporation due to the latent heat, and the cooling has great influence on the evaporation rate. Therefore, heat and mass transfer phenomena are strong-coupled problem. Numerical simulation model to reproduce evaporation phenomenon is desired to investigate the complicated phenomenon, and heat and mass transfer equations are solved with CFD tool: openFOAM. The influences of evaporative cooling on the evaporation rate have been investigated with various droplet sizes and various contact radii. The temperature on the surface of evaporation of a water droplet was measured with a microscopic infrared imaging and a micro probe sensor with a thermoelectric hot junction.
We recently introduced a polariscopy method which can determine feature orientation below the diffraction limit. Measuring transmission at four linear polarisations (0,45,90,135°), information about the orientation of absorbers or patterns and features inside an object could be determined. This is applicable to transmitted/absorbed and scattered/reflected light as well, across the EM-spectrum. We investigate the feasibility of applying this technique to remote sensing satellites. Altimeters are able to determine many oceanographic parameters based on the surface height mapping (e.g., current directions, tidal waves etc). The nature of this measurement means the range and azimuth lateral resolution differs greatly, 100 km to 1 km scale. Synthetic aperture radar (SAR) data contains polarisation information and provides imaging of planetary surfaces. We aim to demonstrate the four polarisation technique in aerial imaging for recognition of feature alignment patterns which are beyond spatial resolution. Information from conventional intensity images (scalar) are augmented by the revealed orientation (vectorial) demonstrated for transmission/scattering in the visible spectrum. Visible as well as SAR imaging timetry can benefit from this augmented resolution.
Here we report on the laser manufacturing of glass true 3D micro-optics. We demonstrate the feasibility of producing individual free-form geometry elements such as lenses, prisms, gratings proving the potential of integration into monolith stacked components. This is achieved by combining ultrafast laser 3D nanolithography and subsequent thermal post-treatment (calcination) - a novel approach introduced for additive manufacturing of inorganic materials [Nanoscale Horiz. 4, 647 (2019)]). The laser made pristine micro-optical components maintain their predefined shape while material is converted from hybrid polymer to glass corresponding to its inherent refractive index and transparency. This approach enables both realization of complex geometries and variation of material properties simultaneously.
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