Measurement Of Temperature Distribution Research Articles

Evaluation of Infrared Thermography for the Detection of Footrot and White Line Disease Lesions in Dairy Sheep.

The objectives of this study were to investigate temperature distribution at the sheep hoof and evaluate the reliability and diagnostic performance of infrared thermography (IRT) for the detection of footrot and white line disease (WLD) lesions in intensively reared dairy sheep. Hoof lesions were clinically assessed, and IRT was used to measure temperature distribution on hoof superficial tissue in 600 multiparous ewes. Binary regression models were developed and validated, and receiver operating characteristic curves were estimated to assess the predictive value and diagnostic performance of IRT for the detection of hoof lesions. The most sensitive prediction model for the detection of IFR was based on the difference between ambient and hoof heel temperature (sensitivity: 83.3%, specificity: 47.8%, and threshold value: 6.5 °C), whereas the most specific prediction model was based on the difference between ambient and coronary band temperature (sensitivity: 51.9%, specificity: 79.7%, and threshold value: 11.3 °C). In the case of WLD, the diagnostic performance of IRT had limited predictive value. IRT could be a useful tool for hoof health screening in dairy sheep. However, it must be cautiously adapted in cases where environmental, operating, and operator variables are not effectively controlled.

Partial discharge performance improvement of covered conductor (CC)/high voltage insulator based electrical distribution systems

In this paper, performance improvement of covered conductor (CC) based distribution systems is achieved through reducing partial discharge (PD) at CC/high voltage insulator (HVI) interface. The reduction of PD is achieved through electric field reduction at CC/HVI interface. The reduction in electric field at CC/HVI interface is done using room temperature vulcanized (RTV) silicone rubber as a coating to high voltage porcelain insulator. The use of RTV coating to improve the performance of CC/HVI systems is evaluated. The evaluation is carried out through electric field calculation considering CC fitted with porcelain insulator as well as the same CC with RTV coating applied to the same porcelain insulator. Electric field calculations at dry and wet polluted conditions are carried out using finite element software (FEM) considering coated and uncoated insulators. Also, experimental validation is carried out through PD current measurement considering dry and wet polluted conditions. Wet pollution condition is carried out at equivalent salt deposit densities of 0.2, 0.4 and 0.6 mg/cm2. The obtained PD current measurements are validated by measuring temperature distribution of the two studied cases using an infra-red (IR) camera. The obtained temperature distribution results from the IR camera validate the obtained results from PD tests.

Fluorescence Anisotropy as a Temperature-Sensing Molecular Probe Using Fluorescein.

Fluorescence anisotropy, a technique to study the folding state of proteins or affinity of ligands, is used in this present work as a temperature sensor, to measure the microfluidic temperature field, by adding fluorophore in the liquid. Fluorescein was used as a temperature-sensing probe, while glycerol–aq. ammonia solution was used as a working fluid. Fluorescence anisotropy of fluorescein was measured by varying various parameters. Apart from this, a comparison of fluorescence anisotropy and fluorescence intensity is also performed to demonstrate the validity of anisotropy to be applied in a microfluidic field with non-uniform liquid thickness. Viscosity dependence and temperature dependence on the anisotropy are also clarified; the results indicate an appropriate selection of relation between molecule size and viscosity is important to obtain a large temperature coefficient in anisotropy. Furthermore, a practical calibration procedure of the apparatus constant is proposed. In addition, the potential of temperature imaging is confirmed by the measurement of temperature distribution under focused laser heating.

Current density and temperature distribution measurement and homogeneity analysis for a large-area proton exchange membrane fuel cell

Homogeneous distribution of electro-chemical reaction rates among the activation surface is critical for improving the performance and durability of automotive proton exchange membrane fuel cells (PEMFCs). Segmented measurement technology is commonly used to characterize the local physical-parameter distribution in the PEMFC. In this study, the local current density (LCD) and temperature distributions of a PEMFC with the activation area of 108 cm2 and various cathode flow fields are experimentally investigated. A homogeneity parameter is introduced to evaluate the homogeneity of LCD distribution. The results show that the performance and LCD distribution uniformity of the cell with dot-parallel flow field are much better than that with parallel and parallel-serpentine flow fields. The temperature distribution is generally positively correlated with LCD distribution. For the LCD distribution, the high LCD region firstly appears in the cathode downstream region, and gradually transfers upstream with increasing the current load. With the increase of inlet humidity, the LCD near the cathode inlet is improved due to the improvement of membrane hydration. Increasing the cathode stoichiometry can effectively improve the uniformity of LCD distribution, and mitigate the local oxygen starvation, especially at high loads.

In Situ Measurement of Temperature Distributions in a Li-ion Cell during Internal Short Circuit and Thermal Runaway

Here we report in situ measurement of temperature distributions in a 2.5-Ah pouch format Li-ion cell during internal short circuit (ISC) and thermal runaway. The ISC and thermal runaway were triggered by nail penetration. The local temperatures were measured by embedded K type micro thermocouples in the middle layer of the experimental Li-ion cell. Highly non-uniform temperature distributions were observed during ISC and thermal runaway as compared with those during constant current discharging and external short circuit. The in situ measurement also captured details of how thermal runaway started from the ISC location and spread to the entire cell in a few seconds. Moreover, the comparison between ISC without thermal runaway and ISC with thermal runaway suggests that internal short circuit resistance plays a critical role in the risk of thermal runaway.

Motion of generated dumbbell-shaped satellite droplets during liquid dielectrophoresis

Actuation of sub-millimeter sized droplets has important implications in heat transfer, microfluidics, and self-cleaning surfaces. Here, we report the motion of satellite droplets generated around a primary droplet actuated using liquid dielectrophoresis (L-DEP). Satellite droplets spanning the electrode gap grow due to the electric field induced enhanced merging of droplets. These satellite droplets attain a dumbbell shape due to the applied field. Interestingly, satellite droplets follow the primary drop interface maintaining a constant gap between themselves and the primary drop. The motion of satellite droplets was captured using high-speed imaging, and the role of temperature gradient was verified by measuring temperature distribution using an IR camera. Through observations and simulations, we qualitatively believe that this behavior arises from (a) repulsive electrostatic and temperature gradient forces; and (b) attractive vapor concentration gradient forces. Simulations were used to estimate the direction of individual forces. Interfacial charges from the applied electric field give rise to the electrostatic repulsion. During L-DEP, the primary droplet heats due to induced current. Thermal conduction through the substrate sets up a temperate gradient, which adds to the repulsion forces between the droplets. Evaporation of the primary droplet leads to the vapor concentration gradient, responsible for the attraction force between the droplets.

Analysis of the temperature distribution in weave-based CFRP during induction heating using a simplified numerical model with a cross-ply representation

Induction heating of carbon fibre reinforced plastics, CFRP, has a great potential within different application areas, such as induction welding and curing of thermosets, due to fast and energy efficient heating. Simulation models can obviously be valuable for example during optimization. This article shows how temperature distribution during induction heating of CFRP based on woven fabric can be simulated using a finite element model with a unidirectional layer representation, thus simplifying the geometry significantly. Electrical and thermal properties were measured and used in the numerical model. The simulated and measured temperature distributions show good agreement, where the prediction of peak temperature is within just a few percent for the plates with a fibre volume fraction above 50% while the same difference is just above 10% percent for the plate with a fibre volume fraction below 40%.

Detailed measurements of in-furnace gas temperature and species concentration distribution regarding the primary-air distribution mode in a spreader and reversal chain-grate furnace

In order to uncover the coal combustion and NOx formation characteristics of chain-grate furnaces and evaluate the effect of the primary-air distribution mode, industrial-size tests with measurements taken of the overall gas temperature distribution in the furnace height direction and gas components (O2, CO, and NO) in the grate zone in a 35 t/h reversal chain-grate furnace were performed at four primary-air distribution modes of the uniform air mode, front-lean air mode, middle-concentrated air mode, and rear-enhanced air mode. Gas temperature decreased continuously in the furnace height direction while showed an increase-to-decrease trend as the grate proceeded. The high-temperature zones with levels below 1350 °C and a small suspension combustion share in the furnace height direction not only confirmed that the primary NOx formation relied on fuel-NO but also ruled against the availability of air staging along the furnace height for NOx reduction. The uniform air mode achieved the highest levels in both burnout and NOx emissions. The other three setups with a sharp air flux reduction in the former air box, decreased apparently NOx emissions while affected burnout to some extent. The rear-enhanced air mode delayed coal combustion with the largest extent and achieved the lowest NOx emissions but highest carbon in slag. In contrast, the middle-concentrated air mode relying on the highest air flux at the central air boxes for strengthening the primary combustion stage, resulted in both NOx emissions and carbon in slag showing acceptable levels of 493 mg/m3 (at 6% O2) and 9.27%, respectively. NOx emissions were reduced by about 18% and meanwhile carbon in slag raised only a limited extent in comparison to the conventional uniform air mode. Therefore, the middle-concentrated air mode was recommended as the optimal primary-air distribution pattern among the four setups.

A novel anode structure for diffuse arc anode attachment

A novel method for adjusting the direct current arc anode attachment mode by changing the anode surface structure is proposed. A transferred arc device is used to investigate the effect on the arc anode attachment state of the electrode separation and the presence and dimensions of an annular boss, or embossing, on the anode. The experimental results show the diffuse arc anode attachment mode is more likely to be formed in the presence of an annular boss structure on the anode, compared to the standard planar structure. In the case of argon working gas, as the distance between the cathode and the anode increases from 15 mm to 30 mm, the arc maintains the diffuse arc attachment on the anode with the annular boss, while for a planar anode, the arc anode attachment mode changes from diffuse to constricted. Comparison of the measured temperature distribution by the relative intensity method and the emission intensity of the arc attachment region verifies that the annular boss anode can indeed promote diffuse attachment. Analysis of the electric field strength distribution between the electrodes shows that the introduction of the annular boss doubles the electric field strength near the anode surface due to the boss edge effect, which drives the arc to be evenly dispersed on the boss, resulting in the formation of diffuse arc attachment. The enlarged attachment area reduces the current density and heat flux on the anode surface, which is important for the stabilization of diffuse arc attachment. No obvious ablation is found on the surface of the annular boss anode after 1 h operation, while there significant ablation is evident on the surface of the planar anode.

Optimization of data acquisition algorithm for temperature and emissivity distribution measurement using snapshot hyperspectral imaging systems

Many industrial and scientific applications require precise measurement of temperature distribution over the surface of the inspected objects with a priori unknown emissivity. In these cases, imaging spectroscopy is an effective approach for quantitative thermography. This method is based on the measurement of thermal radiation spectrum in each pixel and its approximation of Planck's law by selecting proper values of temperature and emissivity. Snapshot hyperspectral imaging systems are especially interesting for this task as they provide an arbitrary number, positions and order of spectral bands and, therefore, enable multiple data acquisition modes. In this paper, we show that conventional equidistant location of spectral bands is not optimal in terms of temperature measurement error minimization. More effective approach is aggregation of the spectral bands into two narrow ranges located around particular wavelengths. We prove these statements by the theoretical consideration, mathematical modeling and experimental study on the tungsten plates using acousto-optical hyperspectral imager. Obtained results may be useful for the development and improvement of quantitative thermography systems with optimized data acquisition modes for various applications.

Publisher's Note: "Measurements of impurity ion temperature and velocity distributions via active charge-exchange recombination spectroscopy in C-2W" [Rev. Sci. Instrum. 92, 053512 (2021)

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Understanding Li-Ion Cell Thermal Runaway through in Situ Measurement of Temperature Distribution

Thermal runaway is a critical safety challenge for Li-ion cells, characterized by rapid temperature rise and potentially rapid energy release. Numerical modeling studies revealed that temperature distribution in Li-ion cells is highly non-uniform during thermal runaway1 , 2. However, there is a lack of experimentally measured temperature distribution results for model validation or insightful understanding of thermal runaway. Here we report development of a Li-ion cell with multiple embedded thermocouples and in situ measurement of its temperature distributions during thermal runaway.As schematically shown in Figure 1, seven micro thermocouples are embedded inside a 2.5 Ah Li-ion pouch cell, enabling in situ measurement of temperatures at different locations. Various testing is performed, including nail penetration testing using a 3 mm-diameter stainless steel nail to trigger thermal runaway. Following our earlier practice3, the nail speed utilized is lower than 0.1 mm/s and the voltages between the nail and cell tabs are monitored.Figure 2 shows the spatial temperature distribution along the centerline during 5C (12.5 A constant current) discharging in comparison with that during thermal runaway as triggered by slow nail penetration. It can be seen that the maximum temperature rise during 5C discharging is about 25 °C and that local temperatures closer to tabs are always slightly higher than those away from tabs. In comparison, maximum temperature rise during thermal runaway is up to 700 °C. More interestingly, the pattern of spatial temperature distribution changes dramatically and is highly non-uniform during thermal runaway. Before 238s, there is little temperature rise and temperature distribution is quite uniform, indicating very slow heat generation near the nail. At 240s, the rise of local temperature closest to the nail is more than 400 °C while the rise of local temperature near the tab is only 20 °C, indicating highly non-uniform temperature distribution and rapid heat generation near the nail. Note that temperature gradient is directionally opposite to that during 5C discharging. Local temperature farther away from tabs but closer to penetration location rises more and faster than that closer to tabs. All of the local temperatures then continue to rise while the temperature gradient becomes smaller, suggesting propagation of thermal runaway from nail penetration location to entire cell. Such detailed spatial-temporal experimental results will help in better understanding of thermal runaway behavior and the development of safer Li-ion cells.

Evaluation of the Self-Cooling Performance of a Flux-Switching Permanent Magnet Machine With Airfoil-Shaped Rotor

The objective of this article is to evaluate the self-cooling performance of a novel integrated flux-switching permanent magnet (FSPM) machine with an airfoil-shaped rotor. The rotor of the proposed integrated machine is functioning as both a rotor of the motor as well as an axial fan. It rotates to draw air from the ambient into the rotor and accelerate the flow through the rotor stage. The high-speed flow provides forced convection to the rotor, stator, windings, and magnets. Therefore, self-cooling is achieved. Accounting for manufacturing challenges of the airfoil blades, three-dimensional (3-D) printed blade caps are designed and assembled over the laminated rotor poles for the airfoil-shaped rotor. The electromagnetic performance of the continuous-skewed stator slot is compared with the step-skewed stator slot. Three housing configurations are proposed in terms of housing with radial inlets, housing with axial inlets, and no housing. The electromagnetic performance is verified by 3-D finite element analysis (FEA). The convective heat transfer coefficients of the three housing configurations are calculated by analytical methods and numerical simulations by 3-D computational fluid dynamics. The effect of encapsulations on the windings is also evaluated by FEA. A prototype machine is built and tested. Experimental results of measured temperature distributions on the stator and windings are included to validate the numerical simulation results.

THERMOGRAPHY – A REVIEW

Thermography is a technique of measurement of skin temperature distribution on the body over a given period of time. It is a noncontact, noninvasive method that utilizes the heat from an object to detect, display, and record thermal patterns and temperature across the surface of the object. Over the years, various devices have been used to measure the amount of heat dissipated by the body and most recently thermography has been emerged to detect the oral and maxillofacial pathologies. It is used to detect malignancies of the maxillofacial region such as vitality of teeth, TMJ disorders, chronic orofacial pain, assessing inferior alveolar nerve decit, and detection of herpes labialis. The present article highlights the history, basic principles, types and applications of thermography and its benecial role in detecting the maxillofacial pathologies in dentistry.

Temperature measurement of turbulent flame using CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy)

In order to satisfy the requirements of high-quality and high-performance optimal material manufacturing process, it is essential to control the gas system of the manufacturing process. In the actual industry, the quality of products is improved by controlling various gases in the manufacturing process. The tunable laser absorption spectroscopy (TDLAS) technique can be measured by the temperature and concentration of target gas simultaneously. Among the more advanced technologies, CT-TDLAS is the most crucial technique for measuring temperature and concentration distributions across two-dimensional planes. This study suggests a three-dimensional useful measurement of irregular flow or exhaust gases. Furthermore, an optical measurement method has been adopted to measure temperature distribution at a cross-section of the Methane Air premixed turbulent flame. The equivalence ratio of fuel can control this system. The burner system consists of two sections (main flame, sub-flame) for a turbulent flame. In the CT-TDLAS technique, it is essential to set the wavelength for target gases. There is a limit to high-temperature measurement in temperature estimation using a single laser-specific wavelength. Therefore, compared measurement performance was made using a mixed type laser (1388 nm, 1343 nm) and a single type laser (1388 nm). The temperatures obtained by using the optical measurement results were relatively evaluated with those obtained by the thermocouples. It was confirmed that the relative error of the temperature occurred at the central position of the burner. It was about 13.33% by the mixed laser system and 38.33% by the single laser system in most close to point from the burner.

Experimental study of the effect of the spray cone angle on the temperature distribution in a can micro-combustor

In this study, the performance of a can micro-combustor of a micro turbine is studied experimentally. The purpose of this study is to show the coupling effect of air flow rate and fuel injection on temperature distribution and flame blowoff limits in the combustion chamber. In this regard, by changing the spray cone angle, the flame structure and the characteristics of the combustion chamber are investigated. In the present study, the liquid kerosene is injected through a pressure swirl atomizer. Experiments have been done for various conditions of air flow rates and fuel injection angles. The combustion zone at the main part of the chamber is investigated by measuring temperature distribution. The results show the significant effect of fuel injection angle on flame structure. By changing the air flow rate, in fact, the effect of fuel injection angle is studied for different overall equivalence ratios from extreme lean to rich conditions. By increasing the fuel injection angle, flame stabilization is accessible even for extreme lean conditions. The more intense combustion zones occur near the liner which can potentially cause structural problems.

Infrared signal of the lobed mixer with external air mixing

AbstractIn order to know the characteristics of reducing the exhaust gas infrared signal of the lobed mixer according to the external air mixing ratio, an infrared signal and temperature distribution measurement using a micro-turbojet engine is performed. A certain amount of compressed air is supplied through an external duct mounted on the micro-turbojet engine exhaust to simulate bypass flow, which is mixed with high-temperature core air and ejected to the atmosphere. The exhaust nozzle used in the experiment is a lobed mixer with a lobe of sinusoidal shape and is designed to have a penetration of 0.2. Exhaust gas temperature and infrared signal are measured according to distance from nozzle outlet under conditions of bypass ratio of 0.5, 1.0 and 1.4. Infrared reduction rates are compared to data without compressed air supply. As a result of the experiment, as the bypass ratio increased, the infrared signal of the exhaust gas and the temperature decrease with bypass ratio increase, and in the case of a bypass ratio of 1.4, the effect of reducing the temperature is observed even at a long distance. In addition, we compared the results of previous studies of a simple cone shape without mixer with infrared reduction effect. The results show that the lobed mixer has a greater effect on reducing the temperature of the exhaust gas and reducing the infrared signal than the cone nozzle. The structure of the mixed jet flow is also studied through Schlieren visualisation and 3D temperature distribution.

Measurements of impurity ion temperature and velocity distributions via active charge-exchange recombination spectroscopy in C-2W.

In TAE Technologies' C-2W experiment, electrode biasing is utilized for boundary control of a field-reversed configuration (FRC) plasma embedded in a magnetic mirror. Understanding the underlying physics associated with FRC rotation, stabilization, and heating is crucial for improving machine performance. Impurity ion rotation and temperature are sensitive to biasing effects, and measurements of these quantities can provide insight into important plasma dynamics and overall effectiveness of the biasing system. To this end, a charge-exchange recombination spectroscopy (ChERS) diagnostic was developed and deployed to measure local impurity ion temperature and velocity in the confinement vessel of C-2W. The system utilizes a new diagnostic neutral beam (40 keV, 8.5A) and a fiber-coupled spectrometer with an image-intensified high-speed camera to measure beam-induced spectral line emission at multiple lines-of-sight. Design details and the first experimental results obtained with this new diagnostic are presented and discussed.

A comprehensive procedure for estimating the stressed-strained state of a reinforced concrete bridge under the action of variable environmental temperatures

This paper reports the full-scale experimental measurements of temperature distribution over the surfaces of bridges' steel-concrete beams under the influence of positive and negative ambient temperatures. It has been established that the temperature is distributed unevenly along the vertical direction of a bridge's steel-concrete beam. It was found that the metal beam accepted higher temperature values. The maximum registered temperature difference between a metal beam and a reinforced concrete slab at positive ambient temperatures was +9.0 °C, and the minimum temperature difference was −2.1 °C. The mathematical models for calculating a temperature field and a thermally strained state of bridges' steel-concrete beams under the influence of variable climatic temperature changes in the environment have been improved, taking into consideration the uneven temperature distribution across a bridge's reinforced concrete beam. The possibility has been established to consider a one-dimensional problem or to apply the three-dimensional estimated problem schemes as the estimation schemes for determining the thermo-elastic state of reinforced concrete bridges. The temperature field and the stressed state of bridges' reinforced concrete beams were determined. It was found that the maximum stresses arise at the place where a metal beam meets a reinforced concrete slab. These stresses amount to 73.4 MPa at positive ambient temperatures, and 69.3 MPa at negative ambient temperatures. The amount of stresses is up to 35 % of the permissible stress values. The overall stressed-strained state of a bridge's reinforced concrete beams should be assessed at the joint action of temperature-induced climatic influences and loads from moving vehicles

Visualizing Spatiotemporal Temperature Variation for Estimating H+ aq Distribution by Pulsed Discharge Plasma Exposure

Positive pulsed discharge plasma is generated above a test liquid containing NaCl in Ar atmosphere, and H+ distribution and a temperature variation in the liquid are, respectively, visualized by colorimetric methods using methyl red (MR) and microencapsulated thermotropic liquid crystals (MTLCs). The discharges generated above the liquid containing MR and MTLCs have almost the same characteristics in the waveforms of discharge voltage and current, and the appearance of discharges. The generation of H+ and the temperature increase in the liquid are induced below the discharge area, and H+ distribution and temperature-increased area expand similarly, by the plasma exposure. The spatiotemporal measurement of temperature distribution in the liquid is also observed with MTLCs using a sheet laser. It is found that temperature increase is measured just below the extremity of the discharge and distributes in a torus form and that no temperature increase occurs below the middle of the discharge area. Since good similarity is observed between the H+ distribution and the temperature increase in the test liquid, H+ distribution probably expands in a concentric configuration from the generation area with the plasma exposure time.