Infrared Thermography Measurements Research Articles

Infrared Thermography and Electrochemical Analysis to Study the Effect of Coating Defects

Evaluation of electrode coatings using in-line non-destructive techniques and understanding the effect of electrode manufacturing defects on lithium-ion battery (LIB) performance is vital to the quality control process and key to reduce the scrap rate during cell manufacturing. In this regard, it is vital to quantify the effect of various defects that are generated during electrode coating process (Layered NMC532 cathode in this study) on LIB performance. To this end, we demonstrate defect detection and porosity measurement using IR thermography and thickness measurement using a laser technique at high line speeds. We show the comparative effects of different defects that were intentionally generated such as agglomeration, pinholes, and non-uniform coating on LIB performance in full coin cells and large pouch cells. The results show that the electrodes with more coated/non-coated interfaces had greater capacity fade than baseline electrodes at high current densities and that pinholes and agglomerates did not affect the performance adversely. In conclusion, these types of characterization of control samples shows the importance of monitoring and early detection of the electrode defects during the coating process for minimization of cell rejection rates prior to fabrication and formation cycling. Acknowledgement: This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) (Deputy Director: David Howell) Applied Battery Research subprogram (Program Manager: Peter Faguy).

Impact of Retrorocket Plumes on Upper-Stage Aerothermodynamics During Stage Separation

In this paper, an extensive investigation of the separation process of the first two stages of a carrier rocket that employs solid rocket motors for the lower stage is presented. As the reference vehicle, the VEGA rocket is used. The effect of the plumes of first-stage retrorockets on upper-stage aerodynamics and aerothermal loads is analyzed by means of wind-tunnel testing in the hypersonic wind tunnel H2K of DLR, German Aerospace Center. Aerodynamic coefficients are determined by force measurements. In addition, pressure distributions on the upper-stage surface and schlieren images for flow visualization are recorded. Infrared thermography measurements are conducted to determine the effect on aerothermal loads. Different flow conditions are achieved by variation of Reynolds number, retrorocket injection pressure ratio, and angle of attack. Results showed extensive flow separation around almost the entire upper stage by the retrorocket plumes already at low injection pressure ratios. During angle-of-attack sweeps, sudden changes in the flow structure occurred accompanied by strong changes in aerodynamic forces at values of . This behavior was found to be influenced by hysteresis effects.

In-flight investigations of the unsteady behaviour of the boundary layer with infrared thermography

Infrared thermography (IRT) has been well established in wind tunnel and flight tests for the last decade. Former applications of IRT were focused, in nearly all cases, on steady measurements. In the last years, requirements of unsteady IRT measurements (up to 10 Hz) have been formulated, but the problem of a very slow thermal response of common materials of wind tunnel models or airplane components has to be overcome by finding a surface modification with a fast thermal response (low heat capacity, low thermal conductivity and high thermal diffusivity). Therefore, lab investigations of potential material combinations and flight tests with a ‘low cost’ aircraft, i.e. a glider with a modified wing surface, were conducted. In order to induce unsteady conditions (rapid change of laminar-turbulent boundary layer transition), special maneuvers of a glider during IRT measurements were performed.

Use of fecal glucocorticoid and salivary cortisol concentrations as a measure of well-being of New York City carriage horses.

OBJECTIVE To use noninvasive approaches to assess stress in New York City (NYC) carriage horses during the course of their daily routine to determine whether use of these horses affected their well-being. DESIGN Prospective case control study. ANIMALS 13 (5 mares and 8 geldings) stabled working NYC carriage horses and 5 pastured (nonworking) NYC carriage horses (1 mare and 4 geldings). PROCEDURES Samples for determination of fecal glucocorticoid and salivary cortisol concentrations were collected on 3 successive days from 10, 8, and 9 working carriage horses during rest (time 1), preparation for work (time 2), and return to the stable (time 3) and at 1 hour after work (time 4). Infrared thermography (IRT) measurements were made to determine maximum temperature of the medial canthus at each time point. Fecal samples were also collected from 5 pastured carriage horses for determination of glucocorticoid concentrations. RESULTS No difference was found in mean ± SE fecal glucocorticoid concentrations between pastured (22.1 ± 9.8 ng/g) and working (19.5 ± 4.2 ng/g) carriage horses. A significant difference was found in salivary cortisol concentrations of working carriage horses between time 3 (0.96 ± 0.06 ng/mL) and time 4 (0.77 ± 0.07 ng/mL). The IRT measurement at time 2 (35.5 ± 0.64°C [95.9 ± 1.2°F]) was significantly lower than that at time 3 (36.2 ± 0.64°C [97.1 ± 1.2°F]). No other differences in IRT measurements were found. CONCLUSIONS AND CLINICAL RELEVANCE These working NYC carriage horses did not have physiologic responses indicative of a negative welfare status.

Spatiotemporal infrared measurement of interface temperatures during water droplet evaporation on a nonwetting substrate

High-fidelity experimental characterization of sessile droplet evaporation is required to understand the interdependent physical mechanisms that drive the evaporation. In particular, cooling of the interface due to release of the latent heat of evaporation, which is not accounted for in simplified vapor-diffusion-based models of droplet evaporation, may significantly suppress the evaporation rate on nonwetting substrates, which support tall droplet shapes. This suppression is counteracted by convective mass transfer from the droplet to the air. While prior numerical modeling studies have identified the importance of these mechanisms, there is no direct experimental evidence of their influence on the interfacial temperature distribution. Infrared thermography is used here to simultaneously measure the droplet volume, contact angle, and spatially resolved interface temperatures for water droplets on a nonwetting substrate. The technique is calibrated and validated to quantify the temperature measurement accuracy; a correction is employed to account for reflections from the surroundings when imaging the evaporating droplets. Spatiotemporally resolved interface temperature data, obtained via infrared thermography measurements, allow for an improved prediction of the evaporation rate and can be utilized to monitor temperature-controlled processes in droplets for various lab-on-a-chip applications.

Application of close-range aerial infrared thermography to detect landfill gas emissions: a case study

Monitoring waste disposal sites is important to check that the produced biogas, potentially explosive, is properly collected by the biogas extraction system of the landfill site and to evaluate the residual biogas flow escaping from upper surface of the landfill. As the biogas migrates to the surface, the soil through which it flows is expected to reach a higher temperature than the surrounding environment; thus, measuring the thermal footprint of the landfill soil surface could allow the detection of biogas leakages and spots suitable for the gas extraction. Close-range aerial infrared thermography is an innovative approach able to identify thermal anomalies with a good resolution over a large region of the landfill surface. A simple procedure to deduce the biogas flow rate emerging from the soil into the atmosphere, based on infrared thermography measurements, is presented. The approach has been applied to a case study concerning a large landfill located in Genoa (Italy). Aerial infrared photographs taken during different days and seasons showed the presence of thermal anomalies over regions along the peripheral boundary of the landfill still not interested in biogas extraction.

Thermal performance evaluation of cascode Paralleled-GaN-HEMTs packaging for high power switching applications

This study investigated the heat generation behavior of normally-on GaN FET consisting of multi-chip AlGaN/GaN high electron mobility transistors (HEMTs) cascoded with a low-voltage MOSFET (LVMOS) and a SiC Schottky barrier diode (SBD) in a new design package to enable high power applications. The electric field intensity distribution and the hot spot position of the devices were analyzed by electrothermal simulation and the infrared temperature measurement. The transient thermal characteristics are probed by temperature sensitive parameters (TSPs). The changes in on-resistance (RON), maximum drain current (IDMAX), and transconductance (gm) with temperature from 25 °C to 150 °C are measured, and the correlations are investigated. Two paralleled GaN-HEMT, LVMOS, and SiC SBD were then integrated on a directly bonded copper (DBC) substrate in the four-pin metal case TO-257 and a newly designed REC-2015 package to evaluate steady thermal performance improvement of packaging. The temperature distribution of parallel-connected GaN HEMTs were analyzed in numerical thermal simulations and infrared thermography measurements. The analytical results of thermal analysis were confirmed by comparing with the infrared thermographic measurements and numerical results obtained from simulations using Ansys Icepak. According to the thermal measurement at power dissipation of less than 24 W, the peak temperatures of the GaN HEMTs are 144.7 °C and 132.6 °C with TO-257 and REC-2015 package.

Infrared thermography with non-uniform heat flux boundary conditions on the rotor endwall of an axial turbine

It is technically challenging to measure heat fluxes on the rotating components of gas turbines, yet accurate knowledge of local heat loads under engine-representative conditions is crucial for ensuring the reliability of the designs. In this work, quantitative image processing tools were developed to perform fast and accurate infrared thermography measurements on 3D-shaped film-heaters directly deposited on the turbine endwalls. The newly developed image processing method and instrumentation were used to measure the heat load on the rotor endwalls of an axial turbine. A step-transient heat flux calibration technique is applied to measure the heat flux generated locally by the film heater, thus eliminating the need for a rigorously iso-energetic boundary condition. On-board electronics installed on the rotor record the temperature readings of RTDs installed in the substrate below the heaters in order to evaluate the conductive losses in the solid. Full maps of heat transfer coefficient and adiabatic wall temperature are produced for two different operating conditions, demonstrating the sensitivity of the technique to local flow features and variations in heat transfer due to Reynolds number effect.

Experimental method to quantify the efficiency of the first two operational stages of nanosecond dielectric barrier discharge plasma actuators

A method to quantify the efficiency of the first two operational stages of a nanosecond dielectric barrier discharge (ns-DBD) plasma actuator is proposed. The method is based on the independent measurements of the energy of electrical pulses and the useful part of the energy which heats up the gas in the discharge region. Energy input is calculated via a back current shunt technique as the difference between the energy given and the energy reflected back. The ratio of the difference of the latter two quantities and the energy input gives the electrical efficiency (ηE) of a ns-DBD. The extent of the energy deposited is estimated via Schlieren visualizations and infrared thermography measurements. Then, the ideal power flux obtained if all the inputted energy was converted into heat is calculated. Transient surface temperature was measured via infrared thermography and used to solve a 1D inverse heat transfer problem in a direction normal to the surface. It gives as output the actual power flux. The estimated ratio between the two power fluxes represents a quantification of the mechanical fluid efficiency (ηFM) of a ns-DBD plasma actuator. Results show an inverse proportionality between ηE, and ηFM, and the thickness of the barrier. The efficiency of the first two operational stages of a ns-DBD is further defined as η = ηE · ηFM.

Film cooling effectiveness enhancement using surface dielectric barrier discharge plasma actuator

The case presented here deals with the enhancement of film cooling effectiveness using plasma flow control. In this experimental study, a jet is injected from an elongated slot into a thermally uniform cross-flow. The influence of a surface plasma dielectric barrier discharge actuator on heat transfer downstream of the slot is investigated. 2D PIV and IR-thermography measurements are performed for three different blowing ratios of M = 0.4, 0.5 and 1. Results show that the effectiveness can be increased when the discharge is switched-on. Whatever the blowing ratio, the actuator induces a deflection of the jet flow towards the wall, increases its momentum and delays its diffusion in the cross-flow. The best results are obtained with a blowing ratio close to 0.5 and an steady actuation without any frequency modulation.

Lasers and infrared thermography: advantageous cooperation.

In a brief review, the beneficial outcomes that have arisen from simultaneous use of laser- and infrared thermography (IRT)-based techniques are demonstrated. The most recent literary and original experimental results collected from different research and practical areas are presented. It is shown that modern IRT acts as an indispensable laser partner in various biomedical and many other applications and technologies. And vice versa, the laser-based methods and techniques often serve as an appropriate research instrument enriching IRT measurement data with independently obtained information.

Combined three-color LIF-PDA measurements and infrared thermography applied to the study of the spray impingement on a heated surface above the Leidenfrost regime

This experimental study deals with the impingement of sprays on a heated wall in close to semi-industrial conditions. Therefore, an experimental set-up was specifically designed: high liquid mass flux (up to 8kg/m2/s), large droplets (up to 300μm) and high surface temperature widely above the Leidenfrost point (up to 800°C). The surface to be cooled is a 175mm diameter nickel disk with 5mm thickness heated by electromagnetic induction. The spraying devices consist in full cone sprays. Several studies, performed under these particular conditions, has allowed characterizing the heat flux removed by the spray by using techniques based on thermocouples or infrared thermography (IRT). However, to investigate more finely the heat transfer mechanism, it is necessary to measure the droplet temperature but, to date, no measurement for sprays are available in the literature. Therefore, the objective of the present work is to demonstrate the ability of the three-color Laser Induced Fluorescence (3cLIF) to meet this challenge. The combination of the 3cLIF with a Phase Doppler system allows also determining the droplet temperature per size class before and after impact. By adding the IRT measurements combined to an inverse heat conduction model, an energy balance is done in order to estimate the evaporated liquid mass. The influence of the normal Weber number on the liquid vaporization is investigated by using three sprays (Normal Weber numbers up to about 1500). Thereby, main results show that the droplets temperature after impact increases with the incident Weber number before to reach a plateau, attributed to the apparition of the splashing regime. The analysis of the energy balance shows that the mass of evaporated liquid decreases with the incident Weber number and the droplet heating. These first results are in well agreement with previous works conducted with single calibrated droplets, validating as the same time the use of combined 3cLIF-PDA measurements in the case of sprays.

Elastocaloric effect in a Co50Ni20Ga30 single crystal

Elastocaloric effect for a Co50Ni20Ga30 single crystal has been investigated. A local adiabatic temperature change (ΔT) of −6K was observed on the removal of a uniaxial stress of 150MPa at 291K. Infrared thermography measurement reveal a correlated response of martensitic bands and temperature mapping. Both elastocaloric effect and superelasticity exhibit a good reversibility in the 100 times of cycling test. The experimentally obtained ΔT value agrees well with the theoretical one by analyzing the temperature dependence of critical stress based on the Clausius-Clapeyron equation.

Transient Heat Transfer in Radiant Floors: A Comparative Analysis between the Lumped Capacitance Method and Infrared Thermography Measurements

The paper presents a simplified mathematical model to describe the transient heat transfer of a radiant floor heating system. A purpose-built test room has been realized to investigate the actual thermal response of a concrete radiant floor in unsteady-state conditions. Beyond the temperature sensors needed for the standard thermal analysis of the heat transfer inside the chamber, the floor temperature was retrieved by means of an infrared thermography camera, in order to validate more precisely the proposed analytical model. The infrared thermography analysis gives interesting information on the floor temperature distribution during the transient, highlighting the pipes’ layout and, if present, inhomogeneous floor zones. The thermal images have been elaborated in order to set and tune the colour map. A portion of the image has been defined for measuring the surface floor temperatures with a previous evaluation of the parameters dealing with the thermographic technique, in order to perform the quantitative survey. The comparison results show that the calculated air and floor temperatures substantially agree with the temperatures measured by infrared thermography and thermocouples, provided that the boundary conditions obtained by the field measurements are strictly reproduced in the lumped capacitance mathematical model. The difference between the two approaches results in values lower than 4 °C during the entire monitoring period: a satisfactory outcome, considering the approximations of the analytical method. The proposed model and its infrared thermography measurements validation represent a useful tool to understand at first sight the floor radiant panels behaviour in the start-up and switch off period, at the aim of gather useful information for the difficult task of their regulation.

Investigation of an impinging heated jet for a small nozzle-to-plate distance and high Reynolds number: An extensive experimental approach

The present work aims at investigating a particular impinging jet configuration throughout a comprehensive experimental approach. A preheated air jet at 130°C issues a fully developed circular pipe at Reynolds number 60,000 and discharges in the laboratory room to impinge a flat plate located 3 diameters downstream. The description of the velocity field and the complete Reynolds stress tensor is provided by stereoscopic particle image velocimetry (S-PIV) and Laser Doppler Velocimetry (LDV) measurements. For the first time, data are reported for the mean and fluctuating temperature of an impinging jet configuration with the help of cold-wire thermometry (CWT) measurements. The heat transfer distribution on the impinged plate is determined through an inverse method based on infrared thermography measurements on the rear face of the plate. The agreement between S-PIV and LDV measurements is shown excellent over the whole flow field. The measured Nusselt number distribution exhibits a secondary maximum at r/D=2, as observed in previous experiments for short impinging distances. Flow dynamics is characterized through a spectral analysis of time-resolved measurements while flow topology features are identified through coherent structure detection based on S-PIV spatially-resolved instantaneous velocity fields. This analysis shows that the jet column mode, associated with a Strouhal number of 0.4, plays a key role in the primary structure dynamics.

Development and evaluation of a fuzzy logic classifier for assessing beef cattle thermal stress using weather and physiological variables

This research was carried out to develop a fuzzy logic classifier that integrates both weather and animal factors to assess individually the level of thermal stress in feedlot finishing cattle. An experiment was performed with two groups of Nellore feedlot finishing cattle for the acquisition of weather and physiological data including the average of surface temperature in different parts of the animal body using infrared thermography. A statistical analysis of the data was applied to seek the best correlation between the weather and physiological measurements and the infrared thermography (IRT) measurements in different parts of the animal body surface and to orient the construction of membership functions. A knowledge-based system was constructed from rules that associate the memberships of the input variables dry bulb temperature, wet bulb temperature and front surface infrared temperature which were found to be suitable for predicting the rectal temperature. Predicted rectal temperature was rated for the level of thermal stress and compared with the real rectal temperature and a traditional temperature–humidity index. The results indicated little correspondence between the fuzzy classifier and temperature–humidity index (29.3%), but the average rectal temperature value during the day showed great consistency (83.2%) between the fuzzy classifier and animal’s response. In addition, the IRT measurements allowed an accurate assessment and classification of the individual thermal stress of animals in the same day. The proposed fuzzy classifier resulted in better estimates of the thermal stress level when compared to the traditional temperature–humidity index and fuzzy-based systems previously developed.

Shifting the Temperature Distribution within Lithium-Ion Pouch Cells Based on Contact and Bulk Resistance Variations at Its Terminals

When spatially resolved models are applied to describe the behavior of lithium-ion pouch cells, the surface temperature of a cell as well as its terminal voltage are usually considered for validation purposes. Examining a cell’s behavior whilst being placed within a climate chamber, the influential heat transfer from the cell to its surroundings can only be estimated due to undirected, turbulent air flow and unknown heat flux along the attached cables. In the work presented here, a laboratory test setup for infrared thermography measurements on lithium-ion cells is introduced which allows for well-defined thermal test conditions and a controlled, directed air flow of 1 m/s to 3 m/s, whereby an overall temperature measurement accuracy of ±0.1 K is achieved. By monitoring the temperature gradient along additional copper bars mounted on the cell’s terminals, the conductive heat flux between the cell and the attached cables can be calculated. The convective heat transfer from the cell’s surface to the surrounding air can be estimated by calculating characteristic dimensionless groups (i.e. Reynolds, Prandtl and Nusselt numbers) from empirical correlations resembling the studied geometry and flow condition. By combining the two approaches, the cell’s energy balance can be calculated for purposes of both cell characterization and model validation. It turns out that the temperature distribution within the cell can be shifted dramatically depending on the electrical and thermal contact conditions prevailing at the cell’s terminals (see Fig. 1, left). We used additional layers of nickel plated steel pads for provoking a resistance increase between the test bench terminals (copper bars) and the cell terminals (tabs). Further, the positive tab’s response towards the artificial resistance increase differs substantially from the negative one (see Fig. 1, right). In literature, a characteristic higher positive tab temperature is often explained as being dependent on the difference in electrical resistance of the positive and negative current collector and electrode layers based on their electrical conductivity and thickness.1 However, the difference in resistance of the positive and negative electrodes seems to be superimposed by an additional resistance arising from a varying goodness of electrical contact between the cables and the positive and negative tabs.2,3 In this work, we extend this approach and investigate four different mechanisms which we assume to be dominating the observed variation in temperature distribution: the contact resistance between the cables and the cell’s tabs, the tab’s electrical bulk resistance, the contact resistance between the tabs and current collectors, and the electrical bulk resistance of the electrodes. To prove our presumptions, a spatially resolved model is prepared for determining the main influencing factors of the studied characteristic inhomogeneous temperature distribution within lithium-ion pouch cells. With the aid of experimental studies carried out by using the presented test setup, the impact of the four mechanisms on the spatial temperature distribution within lithium-ion pouch cells is discussed. Figure 1. Infrared thermographic measurement data (left) and cut lines along the positive and negative terminal (right) of a 40 Ah pouch cell during a 4C discharge rate at an ambient temperature of 25 °C and an air flow speed of 1 m/s flowing parallel to the cell’s planar surface. Varying the electrical contact resistance by including two (2H) and four nickel-plated steel strips (4H) shows to have a dominant influence on the location of the maximum surface temperature being shifted clearly towards the positive cell terminal, however, not on the absolute value of the measured temperature maximum. 1. U. S. Kim, C. B. Shin, and C. S. Kim, J Power Sources, 180, 909 (2008). 2. J. Yi, U. S. Kim, C. B. Shin, T. Han, and S. Park, J Electrochem Soc, 160, A437 (2013). 3. B. Wu, Z. Li, and J. B. Zhang, J Electrochem Soc, 162, A181 (2015). Figure 1

Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

Abstract The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples’ surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

Multi-machine scaling of the main SOL parallel heat flux width in tokamak limiter plasmas

As in many of today’s tokamaks, plasma start-up in ITER will be performed in limiter configuration on either the inner or outer midplane first wall (FW). The massive, beryllium armored ITER FW panels are toroidally shaped to protect panel-to-panel misalignments, increasing the deposited power flux density compared with a purely cylindrical surface. The chosen shaping should thus be optimized for a given radial profile of parallel heat flux, in the scrape-off layer (SOL) to ensure optimal power spreading. For plasmas limited on the outer wall in tokamaks, this profile is commonly observed to decay exponentially as , or, for inner wall limiter plasmas with the double exponential decay comprising a sharp near-SOL feature and a broader main SOL width, . The initial choice of , which is critical in ensuring that current ramp-up or down will be possible as planned in the ITER scenario design, was made on the basis of an extremely restricted L-mode divertor dataset, using infra-red thermography measurements on the outer divertor target to extrapolate to a heat flux width at the main plasma midplane. This unsatisfactory situation has now been significantly improved by a dedicated multi-machine ohmic and L-mode limiter plasma study, conducted under the auspices of the International Tokamak Physics Activity, involving 11 tokamaks covering a wide parameter range with Measurements of in the database are made exclusively on all devices using a variety of fast reciprocating Langmuir probes entering the plasma at a variety of poloidal locations, but with the majority being on the low field side. Statistical analysis of the database reveals nine reasonable engineering and dimensionless scalings. All yield, however, similar predicted values of mapped to the outside midplane. The engineering scaling with the highest statistical significance, , dependent on input power density, aspect ratio and elongation, yields = [7, 4, 5] cm for = [2.5, 5.0, 7.5] MA, the three reference limiter plasma currents specified in the ITER heat and nuclear load specifications. Mapped to the inboard midplane, the worst case (7.5 MA) corresponds to mm, thus consolidating the 50 mm width used to optimize the FW panel toroidal shape.

Numerical simulation and wind tunnel tests investigation and validation of a morphing wing-tip demonstrator aerodynamic performance

This paper presents the results obtained from the numerical simulation and experimental wind tunnel testing of a morphing wing equipped with a flexible upper surface and controllable actuated aileron. The technology demonstrator is representative of a real aircraft wing tip section, and it was developed following a complex, multidisciplinary design process. The model was fitted with a composite material upper skin whose shape can be morphed, as a function of the flight condition, by four electrical actuators placed inside the wing structure. The optimizations were performed with the aim of controlling the extent of the laminar flow region, and the resulting shapes were scanned using high-precision photogrammetry. The numerical simulations were performed using Computational Fluid Dynamics (CFD) and included a model for predicting the laminar-to-turbulent flow transition over the entire wing surface. The analyses included cases with three aileron deflection angles and angles of attack situated within five degrees range. The CFD results were compared with infrared thermography measurements in terms of transition location, surface pressure measurements and balance loads measurements acquired during subsonic wind tunnel tests performed at the National Research Council Canada.