Abstract
Infrared thermography Images of the facial region are taken from sixty persons. Scintigraphy and standard thyroid blood test are used to categorize these persons into thirty-three females ...and thirteen males suffering from Graves’ disease. This study is approved by the All-India Institute of Medical Science Rishikesh Ethics Committee with reference number AIIMS/IEC/19/997. Eleven Females and three males are found to be in healthy conditions and used as control. A convolutional neural networks (CNN) model is developed to automatically segment and extract the histogram-associated information within the thyroid and cheek region from the collected images. The sub-surface temperature of the thyroid gland and control is extracted using these set of images. We have acquired moderately correlated imaging biomarker with respect to age and gender from this sparse data. An Artificial Intelligence-based app is developed and deployed in a clinical environment to enrich the prognosis model in real time. An affordable Thermal plug-and-play addon device is developed to connect with any smartphone for faster diagnosis at the patient end to carry out this test now. This smartphone and AI-based app combination is successfully deployed as a point-of-care device. It is expected that this IR based preliminary test will automatically categorize healthy cases from patients. This step may save the clinicians to unnecessarily recommending the radioactive contamination-prone Scintigraphy and/or expensive and relatively slower thyroid blood tests. Such preliminary tests may (a) save costs to the patients and (b) relieve the burden on pathology labs. These two points are impactful for the healthcare industry, particularly in densely populated countries having low per capita income.
•Experiments with saturated water and ethanol boiling up to CHF were carried out.•Dynamics of vapor bubble growth and separation was studied in wide range of heat fluxes.•Evolution of microlayer ...regions and growth rate of dry spots were measured.•The behavior of two-phase systems near a heating wall at high heat flux was described.
In this paper the results of experimental study of vapor bubbles dynamics at pool boiling of various liquids in a wide range of heat fluxes up to q/qCHF ∼ 0.9 are presented. The experiments were performed at boiling of saturated water and ethanol at atmospheric pressure with the use of high-speed experimental techniques including video macro-visualization and IR thermography from the bottom side of a transparent heated sample. As a result, new data on the growth rate of vapor bubbles and dry spots in their base, evolution of the liquid microlayer region and unsteady temperature field of a thin film heater surface were obtained, and analysis of patterns of process at low heat fluxes was carried out. The usage of high-speed experimental techniques also allowed in this study to investigate the evolution of vapor bubbles with formation of vapor patterns and large agglomerates, to study dry spots dynamics, to estimate void fraction close to heating surface at fully developed nucleate boiling regime up to the critical heat flux depending on liquid properties. Obtained experimental information can be further used to construct more accurate physical models for the theoretical description of microcharacteristics, heat transfer and boiling trigger mechanisms at nucleate boiling of liquids with different physical properties.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
The consequences of tungsten (W) melting on divertor lifetime and plasma operation are high priority issues for ITER. Sustained and controlled W-melting experiment has been achieved for the ...first time in WEST on a poloidal sharp leading edge of an actively cooled ITER-like plasma facing unit (PFU). A series of dedicated high power steady state plasma discharges were performed to reach the melting point of tungsten. The leading edge was exposed to a parallel heat flux of about 100 MW.m
−2
for up to 5 s providing a melt phase of about 2 s without noticeable impact of melting on plasma operation (radiated power and tungsten impurity content remained stable at constant input power) and no melt ejection were observed. The surface temperature of the MB was monitored by a high spatial resolution (0.1 mm/pixel) infrared camera viewing the melt zone from the top of the machine. The melting discharge was repeated three times resulting in about 6 s accumulated melting duration leading to material displacement from three similar pools. Cumulated on the overall sustained melting periods, this leads to excavation depth of about 230
μ
m followed by a re-solidified tungsten bump of 200
μ
m in the JxB direction.
In recent years, the development of advanced materials with enhanced micron-level electromagnetic waves stealth properties has garnered significant attention due to their applications in fields such ...as military technology and thermal insulation. This study primarily investigates the stealth characteristics of materials within the 8–14 μm electromagnetic wave band, commonly known as the infrared (IR) spectrum. The effect of metallic Ag nanoparticles on the graphene oxide (GO) was obtained to achieve the excellent IR stealth ability. Specifically, Ag/GO composite films were prepared using a one-step reduction method and vacuum-assisted drying. The IR emissivity (8–14 μm) of the composites was significantly reduced with increasing Ag content, and the electrical conductivity of the materials was enhanced. When the Ag/GO mass ratio in the material was 1:2, the IR emissivity of the material at 8–14 μm was as low as 0.279, which was 62 % lower compared to GO. In addition, IR thermograms of the composites were analyzed using an IR thermographic camera. Obviously, the composites exhibited significant IR stealth properties when compared with those of GO. Thus, this work provides a reference for the preparation of carbon-based low IR emissivity materials for infrared stealth application.
By changing the content of metal, the obtained samples achieved excellent infrared (IR) stealth properties, which showed a low IR emissivity. In addition, the presence of metal nanoparticles on the surface imparted a certain level of hydrophobicity to the material. Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Cavity- and spear-type TiO2 nanostructures are prepared by hydrothermal treatment.•Nucleation-promoting cavity morphology is superior to spear-like microstructure.•Hydrophobic surface with ...microcavities (CTH) provides HTC enhancement of over 200%.•High nucleation site density on CHT surface narrows surface temperature distribution.•ONB at 2.5 K and Db of 0.55 mm are observed on hydrophobic microcavity surface.
Surface engineering aimed at tuning the wettability and morphology of the boiling surface is a facile approach to moderate and enhance the nucleate boiling process. Key issues include control over the active nucleation site density, bubble departure frequency and liquid replenishment of active nucleation sites while simultaneously reducing the bubble nucleation temperature. In this study, we fabricated spear-type (ST) and cavity-type (CT) TiO2 nanostructures on 25 μm titanium foils via hydrothermal etching in an alkaline solution. High-speed IR and video cameras were used to detect local phenomena in terms of temperature and heat flux fluctuations and observe the bubble dynamics during saturated pool boiling of water. Intrinsically hydrophilic ST and CT surfaces provided a moderate overall enhancement of the heat transfer coefficient compared to an untreated surface due to increased nucleation site density and bubble frequency. The CT surface also decreased the bubble nucleation temperature due to effective vapor-entrapping and nucleation-promoting cavities. In a further step, both surfaces were hydrophobized through chemical vapor deposition of a fluorinated silane to tailor the wettability of the surface into a superhydrophobic state. This further reduced the average surface superheat by at least 40%, while the nucleation frequencies exceeded 200 Hz on the hydrophobized CT surface. In comparison with the untreated reference surface, the heat transfer coefficient on hydrophobized ST and CT surfaces was enhanced by 89% and 237% at 100 kW m−2, respectively. Moreover, the full width at half maximum (FWHM) value of the surface temperature distribution was reduced by 73% and 95% at the same heat flux, respectively. The study confirms that hydrophobic surface treatment can significantly enhance the nucleate boiling process when combined with an appropriate surface structure. Despite the affinity between the vapor and the hydrophobic layer, the cavity-type and spear-type TiO2 structures are able to maintain active nucleation sites well-separated, which prevents the undesirable vapor spreading that possibly leads to an early onset of critical heat flux.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The possibilities for detecting defects in multilayer carbon composites occurring as a combination of layers of carbon fiber fabric with thin layers of epoxy resin (CFRP) are presented in this paper. ...The most common defect in this type of structure is delamination. For non-destructive testing of CFRP samples with deliberately introduced defects, infrared thermography with laser thermal stimulation was used and both computer numerical simulations (using the ThermoCalc program) and experimental tests were carried out. In the experimental testing, a semiconductor laser with a wavelength of 808 nm and a maximum power of 32 W was used for thermal stimulation. Changes of temperature field on the surface of the test sample were recorded with a thermal camera, FLIR 7600 SC. Both pulsed and lock-in thermography methods were used, and this paper presents selected results, together with their analysis. The results presented in this paper show that it is possible to use a laser as a heating source in thermographic non-destructive testing of CFRP composite.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The present experimental study reports the flow and heat transfer characteristics of a synthetic jet issuing from a sharp-edged orifice (diverging-shaped orifice). The experiments are carried out for ...a varied range of opening angles of sharp-edged orifices (θ = 0°, 30°, 60°, 90°, and 120°), Reynolds number (Re = 3243-8143), different jet-to-surface spacings (z/d = 1-16), and for two different values of orifice thicknesses, t = 5 mm (t/d = 0.33) and 10 mm (t/d = 0.66). The hot-wire anemometry is used to study the flow characteristics of synthetic jet, while heat transfer characteristics are studied by using a thermal imaging technique. The time-averaged flow fields associated with sharp-edged orifices reveal that orifices with t = 5 mm and 10 mm exhibit saddle-backed and top-hat velocity profile shapes, respectively. The results show that for a square-edge orifice (θ = 0°), the heat transfer rate decreases with an increase in orifice plate thickness from 5 to 10 mm, while the opposite trend in heat transfer is observed with sharp-edged orifice. The heat transfer rate with a 10 mm thick sharp-edged orifice is higher than the 5 mm thick sharp-edged orifice for all the tested opening angles. Furthermore, the results also show that for sharp-edged orifices, the heat transfer rate increases with the increase in opening angle from θ = 0° to 60°, while it decreases with further increasing from θ = 60° to 120°. The maximum value of average Nusselt number (Nu
avg
) is obtained for θ = 60° for both the orifice thicknesses (t = 5 and 10 mm), and this effect is found to be more pronounced for t = 10 mm orifice. For sharp-edged orifice (θ = 60°), the maximum enhancement in Nu
avg
is found to be 12.66% and 23% higher for t = 5 mm and 10 mm, respectively, compared to the equivalent square-edged orifice (θ = 0°). The cause for variation in heat transfer rate with sharp-edged orifices is interpreted due to the effect of flow recirculation and mass flow rate. A correlation has been proposed for Nu
avg
as a function of different opening angles. The present finding is useful for the optimization of the synthetic jet geometrical parameters for the effective heat transfer rate.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
•At high L0/Ds, Nu distribution is similar to that of a continuous impinging jet.•Maximum stagnation Nusselt number is attained at lower H/Ds as L0/D decreases.•Inner ring-shaped regions of maximum ...Nu are due to the trailing jet.•Outer ring-shaped regions of maximum Nu are due to vortex rings.•Nu fluctuations decrease as L0/D decreases and/or H/D increases.
This study focuses on the combined effect of the nozzle-to-plate distance and of the stroke length on the cooling performances of impinging synthetic jets. Infrared thermography is used as temperature transducer in conjunction with the heated thin foil heat transfer sensor to measure time- and phase-averaged convective heat transfer. All the experiments have been performed at a fixed Reynolds number equal to 5250, while different values of the dimensionless stroke length (L0/D equal to 5, 10 and 20) and nozzle-to-plate distance (H/D between 2 and 10) have been considered. At high L0/D, the heat transfer behaviour resembles that of a continuous impinging jet. It is characterized by a time-averaged stagnation Nusselt number maximum between H/D equal to 4 and 6 and inner and outer ring-shaped regions of Nusselt number maximum at short H/D. These two regions are replaced by a bell-shaped distribution at higher nozzle-to-plate distances. The existence of these regions is clearly observed through the phase-averaged heat transfer measurements. At short H/D, the heat transfer evolution reveals the simultaneous presence of two outer ring-shaped regions. The external outer region is ascribed to the strong coherence of the primary vortex ring, while the internal one is mainly due to the vortex rings generated by the Kelvin–Helmholtz instability along the trailing jet shear layer. At high H/D, the internal outer-ring shaped region disappears because of the weakening of the trailing jet Kelvin–Helmholtz vortex rings. In opposition, at short L0/D, the time-averaged stagnation point Nusselt number is found to have a maximum at lower values of H/D, and no inner ring-shaped region of heat transfer maximum is observed. This region is not present, at low dimensionless stroke lengths, because of the weakness and reduced extent of the trailing jet in the flow field. Indeed, the phase-averaged measurements mainly show the heat transfer caused by the impinging primary vortex ring. Despite the weakness of the trailing jet, the outer ring-shaped region of heat transfer maximum is observed at short H/D because of the presence of a strong primary vortex ring. In addition to that, the dimensionless stroke length and nozzle-to-plate distance also affect the heat transfer fluctuations, which decrease as L0/D decreases and/or H/D increases.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A combination of conventional and un-conventional methods is here used to assess the physical-mechanical properties of some alkaline activated pastes and mortars. The latter were purposely ...synthetized by using Etna ashes as precursor, whose suitability in the alkaline activation process has been ascertained by previous studies. Additionally, the potential reuse of the huge quantities of pyroclastic deposits released into the atmosphere during explosive volcanic eruptions represents an ambitious challenge for the local communities, other than being part of the “Ecological transition” topic promoted by the European Community. The physical-mechanical characterization of the experimental materials has been carried out by using: capillary water absorption test, infrared thermography (IRT), accelerated ageing test by salt mist, uniaxial compressive strength and drilling resistance test. The data obtained for pastes and mortars have been compared to each other and also with traditional materials commonly used in the building sector. The experimental results displayed a strong correlation between the rate of heat dispersion and the microstructure of the samples. In detail, the pastes show a more compact structure than mortars, which is responsible for a slower heat release and a lower capillary water absorption rate, as well as a better mechanical performance. IRT, used for the first time on these materials, revealed a high potential in providing feedback on other physical-mechanical features of alkali activated materials, commonly derived by using destructive methods.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study presents the application of hydrophobic polydimethylsiloxane-silica coating used for the development of biphilic surfaces that are designed to enhance the heat transfer during boiling. ...Surface analyses showed that this coating exhibits a high hydrophobicity due to its hierarchical structure and the use of hydrophobic polymer. An appropriate thermal treatment leads to the oxidation of the methyl groups and a formation of silicon oxide and silicon carbide that result in a wettability transition from hydrophobic to superhydrophilic. On this basis, we manufactured hydrophobic/superhydrophilic patterns on stainless-steel foils using a pulsed Nd:YAG laser. The uniform, superhydrophilic surface exhibited a 350% larger critical heat flux (CHF) than bare stainless-steel foil. High-speed IR thermography revealed that the increased wettability reduced the bubble contact diameter, allowed a higher density of active nucleation sites, and delayed the dry-out. The biphilic surfaces with differently sized hydrophobic spots exhibited the highest heat transfer coefficients, with an up to 200% higher CHF compared to the bare stainless steel. Smaller hydrophobic spots reduced the bubble diameter and increased the nucleation frequency. However, surfaces with larger hydrophobic regions promoted boiling incipience and exhibited higher heat transfer coefficients at low heat fluxes. These results suggest that the optimal biphilic pattern could only be determined for a particular operating point. Our data provide a new insight into the complex phenomena of nucleate pool boiling on chemically and mechanically heterogeneous surfaces.
•Boiling heat transfer on polydimethylsiloxane-silica film is studied experimentally.•Biphilic (138°/<1°) micropatterned surfaces are produced with pulsed Nd:YAG laser.•Smaller hydrophobic spots reduce bubble diameter and increase nucleation frequency.•The highest HTC is achieved on biphilic surface with the smallest hydrophobic spots.•Uniform superhydrophilic surface exhibit 350% higher CHF compared to bare surface.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
