IR Camera Research Articles

The DEPLOY! Project: Development of a Deployable Pulsating Heat Pipe experiment on a parabolic flight

DEPLOY! Project aims at analysing the behaviour of Deployable Pulsating Heat Pipe (PHP) shaped as a helicoidal torsional spring in the adiabatic section on board a Parabolic Flight platform. A PHP is a passive thermal control device where the heat is efficiently transported by means of the self-sustained oscillatory fluid motion driven by the phase change phenomena. The microgravity environment allows to eliminate the buoyancy force contribution in the liquid phase momentum. Consequently, it is possible to isolate the contribution of the pressure drop caused by the 3D arrangement and infer on their effect on the PHP performance. As a result, a proper design based on the previous considerations would increase the flexibility of the PHP for use in space applications without significant reductions in efficiency. The goal of DEPLOY! is to demonstrate the functionality of a Deployable Pulsating Heat Pipe in various unfolding configurations by analysing its thermal-hydraulic response throughout a Parabolic Flight. The presented Deployable PHP is composed of an aluminium tube (inner/outer diameters 1.6mm/2.6 mm) and filled with HFE-7000. It is heated at the evaporator using a flat heater and cooled at the condenser with a water-cooled cold plate. T-type thermocouples are used to measure the wall temperature in several locations, while two pressure transducers (one located in the evaporator section and another in the condenser section of the same pipe) measure the local fluid pressure. Additionally, an IR Camera will be used to observe a section of the pipe for further analysis of the flow frequency. The device operation will be tested on ground and 0-g at different heat loads (24W, 34W), in multiple static positions corresponding to different opening angles (0°, 45°, 90°, 135°, 180°) and during its dynamic opening from 0° to 180°, thanks to a remotely controllable motion system.

Inline Bondwave Monitoring for Direct Bonding, Process Optimization and Impact on Post-Bond Distortion

Direct wafer bonding, named also fusion wafer bonding, is based on the formation of molecular bonds between the two surfaces placed in contact. By the initiation of the contact between the two surfaces the bond is self-propagating: at the initiation point a bondwave is generated, which propagates free until the entire surfaces are in contact (bonded). The dynamic of the bondwave propagation is depending on various material (substrates) and process parameters. As shown by Rieutord et al. (1), and experimentally confirmed (2), for a given material and geometry, the speed is function of adhesion energy and fluid viscosity. For industrial applications, this means that investigating the bondwave speed by inline monitoring can be a way to monitor adhesion energy. Adhesion energy itself is a function of different parameters such as surface roughness, WET treatment or water presence (2,3).Inline IR monitoring can be also a practical solution for defect detection. Compared to post bond IR inspection, the live information allows for easier root cause analysis, e.g., particle defect, surface inhomogeneity or chuck effect. Inline early detection of defective bonds and process outliers enables bonded pairs to be reworked (separated and re-bonded) without any additional metrology steps such as post bonding IR inspection or Scanning Acoustic Microscopy (SAM). In case of fast bondwave, one has to monitor any unwanted effect such as edge voids or increased distortion (4).In an automated fusion bonding equipment, EVG®850LT, a bonding chamber has been equipped with an IR camera to record the bondwave propagation. The chamber has also connected different gas and vent lines and a humidifier to control the bonding atmosphere. The bond is initiated with a mobile pin equipped with a load cell, allowing to start the bondwave in a repeatable way at different locations (each bond must be initiated in a single point, but location might vary between center or edge proximity). As shown in figure 1 for a 300 mm Si-SiO2 bonded pair, spatial information can be extracted from the IR images, allowing for bondwave speed mapping (5). The equipment is also equipped with a plasma chamber for pre-processing. This allows to evaluate, using inline bondwave observation, various process conditions such as: plasma treatment, bond chamber gas type, pressure, humidity and bond pin location. Moreover, a metrology equipment was used for bonded pair shape measurement. This data is used to predict high resolution distortion maps to monitor the effect of bonding wave speed and bonding parameters.Different use cases of bondwave monitoring for process development will be presented, as well as the influence of different process parameters on bondwave propagation. A detailed analysis of the impact of the bond wave speed on bonded stack distortion will be presented. As shown in figure 1 (a) and (b), bonding wave velocity has no impact on high order distortion but will significantly increase the runout or scaling of the bonding pair.1. F. Rieutord, B. Bataillou, and H. Moriceau, Phys. Rev. Lett., 94, 236101 (2005).2. V. Larrey, G. Mauguen, F. Fournel, D. Radisson, F. Rieutord, C. Morales, C. Bridoux, and H. Moriceau, ECS Trans., 75, 145 (2016).3. D. Radisson, Phd thesis, Université Grenoble Alpes, (2014).4. M. Broekaart, A. Castex, K. Landry, R. Fontaniere, and C. Lagahe-Blanchard, ECS Trans., 50, 371 (2013).5. Fournel, F, B Rousset, V Larrey, C Morales, R Sachs, L Sudrie, and C Morvan, WaferBond’22 Proceeding, 2022. Figure 1

Experimental evidence of very short power decay lengths in H-mode discharges in the COMPASS tokamak

Analysis of heat fluxes in scrape-off layer (SOL) plasma is important for the prediction of divertor tile heat loads in future reactor-sized tokamak machines. Typically, the radial heat flux profile can be accurately characterized by the decay length parameter λ q . The predictions are then based on the dependence of λ q on plasma and machine parameters. In recent years, several empirical scaling models were derived from a collective database of decay lengths observed in several large tokamaks as well as two spherical tokamaks. Most recently, a report from the TCV tokamak showed a deviation from several of the proposed models (Maurizio et al (TCV team) 2021 Nucl. Fusion 61 024003). In this work, edge plasma profiles of ELMy H-mode discharges were collected from the COMPASS tokamak database for heat flux analysis. The COMPASS tokamak has a similar machine size and plasma parameters to the TCV tokamak, offering a valuable comparison. The λ q was measured in both downstream and upstream SOL utilizing a divertor probe array validated by an IR camera and Thomson scattering diagnostics. A comparison with the predictions of several scaling models indicated an occurrence of anomalously short (by a factor of 2–5) inter-ELM power decay lengths in both upstream and downstream, as well as a difference in λ q between these two regions. Possible causes related to the accuracy of magnetic reconstruction were eliminated and physics-based sources of apparent compression effects were hypothesized as a motivation for future research.

Experimental analysis of the air- and water-based cooling solution for the three-phase line choke

Modern power systems are affected by current harmonics. The high-order harmonics may result in overheating of the power system and lifetime reduction. Hence, the most novel power systems are equipped with three-phase line chokes. However, power losses generated in three-phase chokes result in a temperature increase within the choke. Most of the commercially available three-phase chokes are equipped with a passive air-based cooling solution. Such a solution results in an increase in the overall size of the device as well as an increase in the manufacturing costs. The water-cooling plates were installed in the commercial three-phase and the cooling performance of the air- and water-based cooling systems were experimentally compared. The chokes were analyzed at the RMS currents that corresponded to 100%, 75% and 50% of the nominal losses of the device. The temperature of the chokes was monitored with the thermocouples and precise IR camera. The comparison of the thermal results showed that the water-cooled choke outperformed the air-cooled unit. The core temperature of the device was reduced from approximately 110 °C to approximately 26 °C for the water-cooled solution compared to the air-cooled one. The temperature distribution in the windings was comparable for both solutions. The highest measured temperature exceeded 100 °C for both cooling solutions. The experimental results presented in this study can be used for further modification of the water-cooling system. Especially, in terms of the water panels’ shape, position and water inlet configuration. Such modifications should lead to further reduction of the device temperature, material and manufacturing costs.

Remodeling of tumor stroma combined with photothermal therapy in the treatment of triple-negative breast cancer

Objective: Polyethylene glycol-modified gold nanostar particles (GNS-PEG) were constructed to investigate whether the degradation of extracellular matrix in triple-negative breast cancer could improve the tumor delivery of GNS-PEG and enhance the efficacy of photothermal therapy. Methods: GNS-PEG were constructed and characterized for physicochemical properties as well as photothermal properties. At the cellular level, the cytotoxicity of halofuginone (HF) and the effect of photothermal therapy were detected. Mouse model of triple negative breast cancer was established by subcutaneous inoculation of 4T1 cells in BALB/c nude mice. Five injections of HF were given via tail vein (HF group), and tumor sections were stained with Masson stain and immunohistochemical staining for transforming growth factor β1 (TGFβ1), α-smooth muscle actin (α-SMA) and CD31 to observe the effect of tumor stromal degradation. Five injections of HF via tail vein followed by GNS-PEG (HF+ GNS-PEG group) were applied to determine the content of gold in tumor tissues by inductively coupled plasma mass spectrometry. The tumor sites of the mice in the GNS-PEG and HF+ GNS-PEG groups were irradiated with NIR laser and the temperature changes were recorded with an IR camera. The tumour growth and weight changes of mice in each group were observed. Ki-67 immunohistochemical staining, TdT-mediated dUTP nick-end labeling and HE staining were performed on tumor tissue sections from each group to observe tumor proliferation, apoptosis and necrosis. HE staining was performed on heart, liver, spleen, lung and kidney tissues from each group to observe the morphological changes of cells. Results: GNS-PEG nanoparticles showed a multi-branched structure with a particle size of 73.5±1.4 nm. The absorption peak of GNS was 810 nm, which is in the near infrared region. The photothermal conversion rate of GNS-PEG was up to 79.3%, and the photothermal effect could be controlled by the laser energy. HF has a concentration-dependent cytotoxicity, with a cell survival rate being as low as (22.8±2.6)% at HF concentration of up to 1 000 nmol/L. The photothermal effect of GNS-PEG was significant in killing tumor cells, with a cell survival rate of (32.7±5.2)% at the concentration of 25 pmol/L. The collagen area fraction, TGFβ1 integrated optical density and α-SMA integrated optical density in the tumor tissues of mice in the HF group were (2.1±0.2)%, 3.1±0.4 and 5.2±1.9, respectively, which were lower than those of the control group (all P<0.01), and the vessel diameter was 8.6±2.9 μm, which was higher than that of the control group (P<0.05). In the HF+ GNS-PEG group, the concentration of gold in tissues was 52.4 μg/g, higher than that in the GNS-PEG group (15.9 μg/g, P<0.05). After laser irradiation, the temperature of the tumor site in the HF+ GNS-PEG group was significantly higher than that in the GNS-PEG group. At the 4th minute, the temperatures of the tumor site in the GNS-PEG and HF+ GNS-PEG groups were 51.5 ℃ and 57.7 ℃ respectively; the tumor volume in the HF+ GNS-PEG group was effectively suppressed. The body weights of the mice in each group did not change significantly during the monitoring period. No significant abnormalities were observed in the main organs of the mice in the GNS-PEG group, but some hepatocytes in the HF and HF+ GNS-PEG groups showed edema and degeneration. Conclusion: The remodeling of extracellular matrix in triple-negative breast cancer could significantly improve the intratumoral delivery of GNS-PEG and thus achieve better photothermal therapy effect.

Multifunctional AuPt Nanoparticles for Synergistic Photothermal and Radiation Therapy.

Photothermal therapy (PTT) has gained considerable interest as an emerging modality for cancer treatment in recent years. Radiation therapy (RT) has been widely used in the clinic as a traditional treatment method. However, RT and PTT treatments are limited by side effects and penetration depth, respectively. In addition, hypoxia within the tumor can lead to increased resistance to treatment. We synthesized multiple sizes of AuPt by modulating the reaction conditions. The smallest size of AuPt was selected and modified with folic acid (FA) for PTT and RT synergy therapy. Various methods including transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FITR) are used to determine the structure and composition of AuPt-FA (AF). In addition, we researched the photothermal properties of AF with IR cameras and infrared lasers. Flow cytometry, colony formation assays, CCK8, and fluorescent staining for probing the treatment effect in vitro. Also, we explored the targeting of AF by TEM and In Vivo Imaging Systems (IVIS). In vivo experiments, we record changes in tumor volume and weight as well as staining of tumor sections (ROS, Ki67, and hematoxylin and eosin). The AuPt with particle size of 16 nm endows it with remarkably high photothermal conversion efficiency (46.84%) and catalase activity compared to other sizes of AuPt (30 nm and 100 nm). AF alleviates hypoxia in the tumor microenvironment, leading to the production of more reactive oxygen species (ROS) during the treatment. In addition, the therapeutic effect was significantly enhanced by combining RT and PTT, with an apoptosis rate of 81.1% in vitro and an in vivo tumor volume reduction rate of 94.0% in vivo. These results demonstrate that AF potentiates the synergistic effect of PTT and RT and has the potential for clinical translation.

Part-scale thermal modelling of the transfusion step in the selective thermoplastic electrophotographic process

The working temperature of any 3D printer has a critical effect on process feasibility as well as the final quality of the product. In this respect, thermal analysis can provide a comprehensive understanding of operation parameters and optimization potential. This most certainly also is the case for the new layer-wise additive manufacturing system, selective thermoplastic electrophotographic process (STEP). In the present paper, we propose a 3D part-scale finite element thermal model for multi-materials which is developed in the commercial software Abaqus/CAE 2021. The reduced-order method, flash heating (FH), is adopted in the model to obtain good accuracy with acceptable simulation time. A specific analysis of the trade-offs between accuracy and CPU-time is carried out by varying the amount of lumping in the meta-layers in the FH method. Furthermore, we conduct an in-house experiment in which we use IR cameras for measuring temperatures during manufacturing, and the results are applied for model validation and calibration. We specifically compare measured and numerically predicted average surface temperatures when steady state is obtained after printing of each layer. Here we obtain a mean error up to 6% depending on the thickness of the meta-layers. Moreover, parametric studies show that pulse duration and heater intensity significantly influence both the surface and bulk temperature profiles, and this provides us with an increased understanding of the thermal behavior of the recently developed STEP process which in turn could make way for further process optimization.

Effects of layer inhomogeneities on the process of sewage sludge convective drying

Convective sewage sludge drying is often carried out in belt dryers, where the air flow is directed through the layer. In such a configuration, drying air properties, as well as the structure of the layer and its homogeneity are key factors affecting the drying process. In the present work, these factors were investigated using laboratory experiments on relatively large sludge samples with a mass of several kilograms. Drying was performed at relatively low drying air parameters (time-averaged temperatures of 65 to 80 °C and velocities of 0.44 to 0.78 m/s). The inhomogeneity of the sludge layer drying was observed by measuring the layer surface temperature with an IR camera. The reduction in layer thickness during drying was measured using an optical laser-based method. Analysis of the data included regression and fitting of the data to parametric drying curves, with the modified Nadhari drying law providing the best fit. The standard deviation of the layer surface thermograms (S) was used as a parameter that accounted for the layer homogeneity and consequently drying evenness. Higher values of S corresponded to lower drying rates and consequently longer drying times, highlighting the importance of producing layers with a homogenous structure. The measured layer thickness reduction rate indicated the overall drying intensity almost from the beginning of drying. Both the surface temperature unevenness and the layer height reduction measurement methods were demonstrated as viable approaches for real-time monitoring of the drying process with potential for application in real-scale dryers.

Image segmentation for automatic detection and detectability evaluation of thinning defects using LSM-based induction thermography

The infrared thermography (IRT) technique is a highly reliable and attractive technique that can evaluate a large area in real-time without destroying the inspection object. This study used the line scanning method (LSM)-based induction thermography (IT) technique among active IRT to detect thinning defects in S275 steel specimens. Unlike the dynamic mode, LSM was applied to perform sequence processing so that the copper coil shape was removed in the 2D thermal images processed. After image segmentation, a binary image was acquired using the Otsu algorithm. By utilizing image segmentation, the applied threshold for each defect is different when performing the Otsu algorithm. This makes it possible to compare defect detection according to the presence or absence of image Segmentation. Automatic defect detection was performed using a Boundary Tracking algorithm, and 12 defect detections were confirmed. Accuracy was evaluated through pixel calculation, and defects in A, B, and D columns showed high detection accuracy. This study presented the principle of LSM in which includes the relative movement between the IR camera and the specimen. In addition, a mechanism to increase the number of defects detected through image segmentation was presented.

Physics and Technology Research for Liquid-Metal Divertor Development, Focused on a Tin-Capillary Porous System Solution, at the OLMAT High Heat-Flux Facility

The operation of the Optimization of Liquid Metal Advanced Targets (OLMAT) facility began in April 2021 with the scientific objective of exposing liquid-metal plasma facing components (PFCs) to the particle and power fluxes provided by one of the hydrogen neutral beam injectors of the TJ-II stellarator. The system can deliver heat fluxes from 5 to 58 MW m−2 of high energy hydrogen neutral particles (≤ 33 keV) with fluxes up to 1022 m2 s−1 (containing an ion fraction ≤ 33% in some instances), pulsed operation of 30–150 ms duration and repetition rates up to 2 min−1. These characteristics enable OLMAT as a high heat flux (HHF) facility for PFC evaluation in terms of power exhaust capabilities, thermal fatigue and resilience to material damage. Additionally, the facility is equipped with a wide range of diagnostics that includes tools for analyzing the thermal response of the targets as well as for monitoring atomic/plasma physics phenomena. These include spectroscopy, pyrometry, electrical probing and visualization (fast and IR cameras) units. Such particularities make OLMAT a unique installation that can combine pure technological PFC research with the investigation of physical phenomena such as vapor shielding, thermal sputtering, the formation/characterization of plasma plumes with significant content of evaporated metal and the detection of impurities in front of the studied targets. Additionally, a myriad of surface characterization techniques as SEM/EDX for material characterization of the exposed PFC prototypes are available at CIEMAT. In this article, first we provide an overview of the current facility upgrade in which a high-power CW laser, that can be operated in continuous and pulsed modes (0.2–10 ms), dump and electrical (single Langmuir) probe embedded on the target surface have been installed. This laser operation will allow simulating more relevant heat loading scenarios such as nominal steady-state divertor heat fluxes (10–20 MW m−2 in continuous mode) and transients including ELM loading and disruption-like events (ms time scales and power densities up to GW m−2 range). The work later focuses on the more recent experimentation (2022 fall campaign) where a 3D printed Tungsten (W) Capillary Porous System (CPS) target, with approximated 30 μm pore size and a 37% porosity and filled with liquid tin. This porous surface was a mock-up of the PFC investigated in the ASDEX Upgrade divertor manipulator. The target composed with this element was eventually exposed to a sequence of shots with the maximum heat flux that OLMAT provides (58 ± 14 MWm−2). Key questions as resilience to dry-out and particle ejection of the liquid metal layer, its refilling, the induced damage/modification of the porous W matrix and the global performance of the component are addressed, attempting to shed light on the issues encountered with the PFC at tokamak scale testing.

Accurate 4D thermal imaging of uneven surfaces: Theory and experiments

Conventional IR thermography is basically a 3D imaging model: pixel position (2D) and temperature (1D). However, the surface roughness, which cannot be depicted by the 2D geometry imaging, may introduce significant error into the temperature measurement, especially in close range. Although there are some principle studies on this theme, quantitative tools for arbitrary-shaped surfaces is still lacking. In this work, we have developed an imaging system composed of a binocular camera using structured illumination and an IR camera to reconstruct 4D uneven surface thermal images. This 4D information includes the 3D geometry of the surface and the temperature mapping over it. Based on the highly accurate surface roughness image obtained, a meshed area calculation tool is used to establish a temperature self-correction module for rough/uneven surfaces, which include convex surface, concave surface or their combinations. The effective emissivity of convex as well as flat surface is easy to calculate, because is this case, there is no inter-radiation or reflection. On contrast, the determination of concave surface emissivity is still posed as a challenge. In this work, some theoretic gap was first filled and then the experimental verification was provided. The temperature-correction takes angle of view and emissivity calibration into account. The angle of view is relative to the position of the object point and the emissivity calibration is based on the 3D geometry of the uneven surfaces. An imaginary flat surface is used to provide an effective emissivity for a local roughness. Experimental results shows that without this temperatue-correction module, the deviations between IR thermography and thermocouple are from ∼2.35 °C (at 50 °C) to ∼4.96 °C (at 300 °C) and from ∼2.43 °C (at 50 °C) to ∼4.78 °C (at 300 °C), while after the correction, the deviations are from ∼0.12 °C (at 50 °C) to ∼0.20 °C (at 300 °C) and from ∼0.16 °C (at 50 °C) to ∼0.20 °C (at 300 °C). Utilizing the thermal imaging model for recorrection, the deviations are from ∼0.13 °C (at 50 °C) to ∼0.19 °C (at 300 °C) and from ∼0.16 °C (at 50 °C) to ∼0.19 °C (at 300 °C). This generalized solution paves the way for high-accuracy temperature measurement on complexly rough surface, especially for high temperature, at which the measuring deviation can be very large.

Investigations on thermal contact resistance between filled polymer composites and solids using micro thermography

This article reports the use of a new measurement technique based on micro thermography for determining the thermal contact resistances (TCRs) between filled polymers and solids. The thermal conductivity of polymers can be significantly increased by using thermally conductive fillers. For numerous applications, not only is a high intrinsic thermal conductivity required but also a good thermal transfer between the filled polymer and an adjacent solid surface. The physical principles of thermal transport when considering this type of contact have not yet been investigated in detail, and only a few experimental results are available. The most common measurement techniques determine a macroscopic resistance and project it onto the contacting surface. However, the heterogeneous microstructure of a filled polymer causes the TCR to be a volumetric phenomenon in the overall boundary region. The utilized IR camera system takes thermal images with a spatial resolution of less than per pixel. The new method resolves the TCRs spatially and gives new insights into the microscale effects on the particle level. In addition to the common zero-gap extrapolation for the extraction of TCRs, we propose another evaluation method that considers all microscale effects of the boundary layers and evaluates TCR as a volumetric phenomenon. For the first systematic study, samples consisting of two aluminum substrates and a filled epoxy polymer were prepared and investigated. We studied the effects of filler size, filler material, filler volume fraction, and surface structure, focusing on monomodally filled polymers with filler amounts between and . The obtained results and the uncertainties of the new method are discussed within this paper.

Infrared in-line monitoring of flaws in steel welded joints: a preliminary approach with SMAW and GMAW processes

The non-destructive full-field non-contact thermographic technique is applied for non-destructive flaw detection of the welded joints, in real-time and offline configuration. In this paper, a thermographic procedure for real-time flaw detection in manual arc welding process is presented. Surface temperature acquisitions by means of an IR camera were performed during arc welding process of 8 specimen both for calibration and validation of the numerical model. The investigated variables are the technique (manual stick arc (SMAW) and gas arc (GMAW) welding) and the joint shape (butt and T joint) for steel joints, in sound conditions and with artificial flaws. Numerical simulation of welding thermal transients was run to obtain the expected surface temperature fields and thermal behavior for different welding parameter configurations. Hardness measurement and micro-graphic analysis were performed to validate numerical simulation results. The real-time thermographic study of the weld pool gives direct indications of anomalies; local studies of the thermal transient and thermal profiles can detect some kind of flaws; microstructural analysis of Heat-Affected Zone (HAZ) and surrounding areas higlights the presence of austenite and martensite distribution which justifies the thermal transients and thermal profiles for different welding configurations. Comparing real-time IR acquisition of the welding process with simulated thermal contours of sound processes provides information of presence of some kind of flaws. Since most of the flaws are generated in the weld pool, it is possible to recognize anomalies directly from the thermal acquisitions or with post-processing the acquired data.

Infrared imaging for detection of defects in concrete structures

Deterioration of concrete structures is an issue that affects the entire world and is brought on by various causes like climatic conditions, aging, attack of aggressive media, etc. Periodic inspections and proper maintenance are crucial to prevent the degradation of structures. Conventionally, the condition of the structures is monitored visually but over a while, non-destructive evaluation (NDE) technologies have gained significance and are expected to be successfully used for the inspection and management of civil structures. Infrared imaging is an effective NDT tool to monitor the health of civil structures. In this study, Infrared Thermography (IRT), an image-based method, is introduced and implemented for the assessment of concrete structures. Experiments on cement concrete cubes were conducted to investigate and enhance the applicability of the infrared thermography technique. The results are quite promising and helps to detect defects like delamination, voids, and cracks, etc. as the IR camera can pick-up the difference in temperature between sound and defective regions. However, the utilization of IRT for inspection poses many challenges but they can be overcome by combining it with other techniques like finite element method, acoustic emission and ultrasonic guided waves. Hence, the infra-red thermography technique is an excellent technology for practically evaluating concrete structures.

Online process monitoring of direct laser interference patterning using an infrared camera system

Direct laser interference patterning enables the fabrication of homogeneous microstructures in the sub µm range. Generally, the topography of fabricated structures is characterized ex-situ using for instance confocal microscopy or white light interferometry. These methods require at least few seconds to fulfill a measurement and therefore are not suitable for online process observation. In this study, an IR camera system is used for the first time, for capturing the average temperature during the DLIP treatment in real time. To determine a correlation between the average temperature and the topographical parameters, the treated surfaces are analyzed using confocal microscopy. A linear dependency between the applied laser fluence (in the range from 0.7 to 4.9 J/cm2) and the average measured temperature could be established. In addition, in this fluence range, significant changes in the surface roughness, skewness and kurtosis occurred, which could be associated to a certain process average temperature.

The Dangers of Analyzing Thermographic Radiometric Data as Images.

Thermography is probably the most used method of measuring surface temperature by analyzing radiation in the infrared part of the spectrum which accuracy depends on factors such as emissivity and reflected radiation. Contrary to popular belief that thermographic images represent temperature maps, they are actually thermal radiation converted into an image, and if not properly calibrated, they show incorrect temperatures. The objective of this study is to analyze commonly used image processing techniques and their impact on radiometric data in thermography. In particular, the extent to which a thermograph can be considered as an image and how image processing affects radiometric data. Three analyzes are presented in the paper. The first one examines how image processing techniques, such as contrast and brightness, affect physical reality and its representation in thermographic imaging. The second analysis examines the effects of JPEG compression on radiometric data and how degradation of the data varies with the compression parameters. The third analysis aims to determine the optimal resolution increase required to minimize the effects of compression on the radiometric data. The output from an IR camera in CSV format was used for these analyses, and compared to images from the manufacturer's software. The IR camera providing data in JPEG format was used, and the data included thermographic images, visible images, and a matrix of thermal radiation data. The study was verified with a reference blackbody radiation set at 60 °C. The results highlight the dangers of interpreting thermographic images as temperature maps without considering the underlying radiometric data which can be affected by image processing and compression. The paper concludes with the importance of accurate and precise thermographic analysis for reliable temperature measurement.

The flow and heat transfer behavior of synthetic jets with star shaped orifice of different lobes

In the present experimental investigation, the flow and heat transfer characteristics of synthetic jet (SJ) issuing from different lobed (3–10) star-shaped orifices are studied. Tests are performed by actuating the SJ actuator at constant input power of 4Vrms, with varied range of orifice to surface spacings (1–16) and numerous values of Reynolds number (8692–10746). The synthetic jet's flow characteristics are studied using hot-wire anemometry, while the thermal characteristics are analyzed using an IR camera. Distinct peaks in turbulence intensity are observed in major and minor planes for different lobed (3–6) star orifices; this may be due to the development of two shear layers in such orifices, which consequently merges into a single shear layer for higher lobed (8–10) star orifice. The 6-lobed star orifice is found to exhibit maximum heat transfer performance at z/d varying between 2 and 14. At z/d = 2, the 6-lobed star orifice exhibit 7.6% and 10.1% improvement in average Nusselt number compared to circular and 10-lobed star orifice respectively, which may be due to formation of vortical structures along the lobed edges and subsequent switching of axes between the major and minor planes. To comprehend the energy associated with the issuing vortices, the power spectral density of the velocity signal at the orifice exit is examined. A unified correlation for the average Nusselt number is also derived for various star-shaped orifices.

Conceptual design of cost-effective ice detection system based on infrared thermography

Ice accretion has been a persisting issue in cold regions and poses a threat to both onshore and offshore infrastructure, especially to sensitive equipment and personnel safety. Thermal infrared imaging (thermography) can be used as a non-destructive, non-invasive technique to determine the presence and thickness of ice over a surface. This paper presents early-stage experiment results with a FLIR® Lepton 2.5 radiometric thermal IR camera (resolution80×60) to detect ice. Other technical aspects are also studied qualitatively, and corresponding results are validated against a high-speed, high-resolution FLIR® T1030SC thermal IR camera. The presented results are the first step in detecting and mitigating ice on flat surfaces. This technique may lead to the development of autonomous, remote, economical ice detection and mitigation system.

Eddy current soldering of solar cell ribbons under a layer of glass

Thermal fatigue of soldered interconnections of silicon solar cells is considered one of the key failure modes in photovoltaic (PV) modules. Due to differences in thermal expansion coefficients of the used materials, cracks and disconnected wiring can occur, causing a local increase of resistance. This can lead to hot spots and early failure of a panel. In this research, we develop eddy current soldering as a non-contact soldering technique for tabbing the ribbon of PV cells under a layer of glass. The performance of eddy current soldering was studied in detail by changing an induction coil distance to the treated sample from 2 to 4 mm and varying exposure time. An IR camera monitored temperature profiles at the soldering zone, and I–V curves of samples were extracted to validate the soldering technique and the efficiency of the tabbing process. Electroluminescence imaging was deployed to monitor cracking after the soldering process; scanning electron microscopy (SEM) and scanning acoustic microscopy (SAM) were used to investigate the microstructure and cracking within the solder joint and silicon. The results showed that the shortest exposure times at a 2 mm heating distance caused higher risks for cracks in silicon. The intermediate exposures at a 3 mm heating distance increased the likelihood of cracking in the solder joint. For the longest heating times at a distance of 4 mm, the solder joint appeared crack free, although, in some areas, poor wetting of solder was observed. The performance of eddy current soldering under a layer of glass was compared to manually soldered samples. Based on the I–V curves, all samples were functional, and differences between exposure times and manually soldered samples were not evident. Thus, only electrical verification of the solder quality was insufficient. Due to the study, it was concluded that the proper solder interconnections through glass could be made by using the eddy current soldering process and a sufficient exposure time to avoid cracking within the solder joint configuration and silicon.

How roughness and thermal properties of a solid substrate determine the Leidenfrost temperature: Experiments and a model

Understanding and regulating the Leidenfrost temperature is of great importance for practical applications such as spray cooling. In this study, nonnegligible cooling effects of Leidenfrost drops on surfaces with small thermal diffusivities are observed with an IR camera. The influence of thermal properties and surface roughness on the Leidenfrost temperature is investigated experimentally and explained by a simple theoretical model.