Surface Temperature Measurements Research Articles

Hypergolic ignition response to oxidizer droplet properties

The hypergolic ignition response to oxidizer droplet properties is an important consideration for oxidizer injector design in hybrid rocket motors. Hence, the present work focused on hypergolic ignition characterization as a function of droplet properties and impact dynamics for a promising propellant. The propellant for the present work consisted of rocket grade hydrogen peroxide (RGHP) as oxidizer, high-density polyethylene (HDPE) as fuel and sodium borohydride (NaBH4) as the hypergolic additive embedded in the HDPE matrix. This propellant was chosen for this detailed study since it showed promising results in prior studies, exhibiting low (<10 ms) ignition delays. For this work, in a drop-test setup, RGHP droplet diameters between 1.90±0.11 mm and 4.35±0.26 mm were dropped on the HDPE + NaBH4 fuel samples at velocities between 0.3 m/s to 1.93 m/s. The ensuing ignition event was studied using both visible and infrared high-speed imaging. Post-impact droplet parameters were determined to enable a deeper analysis of observed phenomena. While ignition delay was the focus of this work, flame spread areas and heat release were also studied. Higher impact velocities generally led to lower ignition delays while splashing oxidizer drops increased probability of larger flame areas and higher heat release. Additionally, the initial ignition/heat release event was found to originate in a small region at the thinnest area of the post-impact droplet. Surface temperature measurements were also performed using infrared imaging. The data suggested that the initial heat release was found to be likely due to RGHP-NaBH4 reaction with no contribution from RGHP decomposition. Regression and random forest machine learning analysis found ignition delay depended strongly on the minimum post-impact drop layer thickness. Based on the data analysis, a simple mathematical model was developed whose results matched experimentally observed trends. The study is expected to further understanding of the processes that control hypergolic ignition in addition to aiding rocket engineers design better oxidizer feed systems. Novelty and SignificanceThis work constitutes a novel in-depth study on the influence of drop impact properties on hypergolic ignition. Using innovative techniques, this work is the first to show the overwhelming importance of residual droplet layer thickness on ignition delay. Additionally, a simple mathematical model based on that finding performed well against experimental data which is of substantial significance, given the complex and multi-parametric nature of hypergolic ignition. Finally, the work establishes that operating in the splashing regime enhances heat release and flame spread. The candidate propellant for this work was hydrogen peroxide and high-density polyethylene with embedded NaBH4. However, the findings of this study are likely generalizable over a range of solid-liquid hypergolic propellants involving solid fuels with embedded energetic materials, of which there are many. The findings of this work can enhance understanding of hypergolic ignition in addition to aiding in better rocket injection system design.

Lunar grain size determination based on surface temperatures using ensembles of thermal model parameters

Surface temperature measurements of airless bodies provide an opportunity to estimate regolith thermal properties via inverse modeling. However, thermal models involve many unknown parameters. Here an ensemble of thermal model calculations is applied to lunar nighttime surface temperatures in order to constrain the mean particle size of near-surface regolith materials. We find that many parameter combinations can produce the same surface temperatures, but a likely apparent grain size can be inferred without ad-hoc assumptions for other parameter values as long as grain size is among the leading causes for geographic variations in temperature.

Data Reconstruction of Sea Surface Temperature in Indonesia’s Fish Management Area 713 (IFMA-713) Using Machine Learning

The IFMA-713 in Indonesia is water that has dynamic of temperature changes due to interactions with the Pacific Ocean and the surrounding. Sea surface temperature data can be obtained by measuring with satellite imagery. However, satellite imagery measurements of sea surface temperature can be incomplete due to cloud cover. In this study, a machine learning method was used to reconstruct sea surface temperature data using a backpropagation neural network algorithm. The data used in this research is data captured with MODIS Satellite. Then, the reconstruction of sea surface temperature data is carried with four scenarios with missing data percentages: empty data, zero values, average values at the point of data collection, and Indonesia’s average sea surface temperature. Accurate results were obtained in reconstructing sea surface temperature where the scenarios had a positive correlation. The most accurate scenarios for reconstructing sea surface temperature data with missing data were those in which the empty data was filled with average values at the point of data collection or Indonesia’s average sea surface temperature.

Effect of Pressure and Turbulence Intensity on the Heat Flux During Flame Wall Interaction (FWI)

Combustion applications such as internal combustion engines are a major source of power generation. Renewable alternative fuels like hydrogen and ammonia promise the potential of combustion in future power applications. Most power applications encounter flame wall interaction (FWI) during which high heat losses occur. Investigating heat loss during FWI has the potential to identify parameters that could lead to decreasing heat losses and possibly increasing the efficiency of combustion applications. In this work, a study of FWI (CH4-air mixture) in a constant volume chamber, with a head-on quenching configuration, at high pressure in both laminar and turbulent conditions is presented. High-speed surface temperature measurement using thin junction thermocouples coupled with high-speed flow field characterization using particle image velocimetry (PIV) are used simultaneously to investigate the effect of pressure during FWI (Pint) and turbulence intensity (q) on the heat flux peak (QP). In laminar combustion regimes, it is found that QP is proportional to Pint0.35. The increase in q is shown to affect both Pint and QP. Finally, comparing QP versus Pint for both laminar and turbulent combustion regimes, it is found that an increase in q leads to an increase in QP (b = 0.76).

Remote sensing‐based geostatistical hot spot analysis of Urban Heat Islands in Dhaka, Bangladesh

Urban Heat Island (UHI) refers to a phenomenon whereby urban areas experience higher temperatures compared to the surrounding areas. Remote sensing‐based Land Surface Temperature (LST) measurements can be utilized to measure UHI. This study emphasized on geostatistical remote sensing‐based hot spot analysis () of UHI in Dhaka, Bangladesh as a way of examining the influences of Land Use Land Cover (LULC) on UHI from 1991 to 2015. Landsat 5 and 7 satellite‐based remote sensing indices were used to explore LULC, UHI and environmental footprints during the study period. The Urban Compactness Ratio (CoR) was used to calculate the urban form and augmented characteristics. The Surface Urban Heat Island (SUHI) intensity (ΔT) was also used to explore the effects of UHI on the surrounding marginal area. Based on our investigations into LULC, we discovered that around 71.34 per cent of water bodies and 71.82 percent of vegetation cover decreased from 1991 to 2015 in Dhaka city. Contrastingly, according to CoR readings, 174.13 km2 of urban areas expanded by 249.77 per cent. Our hot spot analysis also revealed that there was a 93.73 per cent increase in hot concentration zones. Furthermore, the average temperature of the study area had increased by 3.26°C. We hope that the methods and results of this study can contribute to further research on urban climate.

Tb3+/Mn4+ co-doped SrLaMgNbO6 green/red dual-emitting phosphors for optical thermometry

Remote and noncontact surface temperature measurements are frequently required yet challenging to execute. One the most promising options consists in using rare earth or transition metal doped materials as optical (luminescence) temperature sensors. In this paper, a series of novel Tb3+/Mn4+ co-doped SrLaMgNbO6 (SLMN) phosphors have been synthesized and thoroughly investigated for their structural, luminescence spectroscopic and decay kinetics properties as well as for temperature sensing performance. X-ray powder diffraction (XRD) analysis has shown that the prepared sample presents a double perovskite structure. Upon the UV excitation, emission spectra of SLMN:Tb3+, Mn4+ exhibit green and red emission bands for Tb3+ and Mn4+ dopants, respectively. Temperature-dependent photoluminescence (TD-PL) studies revealed sever thermal quenching of Mn4+ emission while that of Tb3+ was moderate providing well pronounced difference in fluorescence intensity ratios (FIR) of the ions. The maximum relative sensitivity (Sr) was found to be 3.27% K−1 and 1.92% K−1 for Mn4+ and Tb3+, respectively. This implies that SLMN: Tb3+, Mn4+ phosphor is a viable candidate material for a dual-mode optical temperature detection.

A data-assimilative modeling investigation of Gulf Stream variability

An advanced data-assimilative ocean circulation model is used to investigate Gulf Stream (GS) variability during 2017–2018. The modeling system applies a strong-constraint, 4D variational data assimilation algorithm. It assimilates satellite-based sea surface height and sea surface temperature measurements and in situ temperature and salinity profiles. Model skill assessment metrics along with comparisons of GS position and GS's three-dimensional mean kinetic energy with historical observations are applied to validate the data-assimilative model. The resulting time- and space-continuous ocean state estimates are used to diagnose eddy kinetic energy conversion and cross-stream eddy heat and salt fluxes over the two-year study period. The processes leading to kinetic energy conversion are primarily due to GS meanders. Significant inverse energy cascading (EKE→MKE and EKE→EPE) can occur during GS-eddy interactions, particularly during onshore intrusions or offshore meanderings of the GS. Throughout the two-year study period, the cross-stream eddy heat and salt fluxes off Cape Hatteras were predominantly positive (onshore). Both GS offshore meandering (occurring 44% of the time and associated with shelf/slope water export) and GS intrusion (occurring 56% of the time) contribute to onshore heat and salt transport. Improved understanding of these processes and dynamics requires strong integration of an advanced observational infrastructure that combines remote sensing; fixed, mobile, and shore-based observing components; and high-resolution data assimilative models.

Energy Efficiency Assessment for Buildings Based on the Generative Adversarial Network Structure

Thermal images are highly dependent on outside environmental conditions. This paper proposes a method for improving the accuracy of the measured outside temperature on buildings with different surrounding parameters, such as air humidity, external temperature, and distance to the object. A model was proposed for improving thermal image quality based on KMeans and the modified generative adversarial network (GAN) structure. It uses a set of images collected for objects exposed to different outside conditions in terms of the required weather recommendations for the measurements. This method improves the diagnosis of thermal deficiencies in buildings. Its results point to the probability that areas of heat loss match multiple infrared measurements with inconsistent contrast for the same object. The model shows that comparable accuracy and higher matching were reached. This model enables effective and accurate infrared image analysis for buildings where repeated survey output shows large discrepancies in measured surface temperatures due to material properties.

Digital infrared thermal imaging of udder skin surface temperature: a novel non-invasive technology to monitor calving process in Murrah buffalo (Bubalus bubalis)

Quantifiable decline in the maternal body temperature during the pre-calving offers the possibilities for predicting the calving that can improve the calving management. As infrared thermography (IRT) is a simple non-contact tool for precise measurement of surface temperature, we investigated the use of IRT to establish thermal signatures around calving in the Murrah buffalo. The IRT of eye, right lateral, left lateral and rear side of udder skin surface temperature (USST) were recorded at 6 h interval from 96 h before the expected date of calving, at the time of calving and 24 h post-calving in Murrah buffaloes (n = 28). In parallel, blood samples were collected for progesterone (P4) assay. The results revealed that the IRT of the eye, right and left lateral and rear side of USST showed a significant decrease in the temperature from 48 h pre-calving till the onset of calving with a ΔT (°C) of 0.56, 0.91, 0.70, and 0.90, respectively. Mean USST significantly declined from 48 h pre-calving with a ΔT of 0.85 °C. The residual temperature of both eye and various ROI of the udder also followed a similar and significant declining trend from 48 to 0 h of calving indicating that circadian influence on the USST was minimum. Plasma P4 concentration significantly decreased from 72 h pre-calving till calving. It is concluded that a marked reduction in the IRT of the USST at 6–12 h pre-calving would be useful in predicting the onset of calving in the Murrah buffalo.

Spatio-temporal solid-state electrocaloric effect exceeding twice the adiabatic temperature change

In an all-solid-state electrocaloric arrangement, an absolute temperature change which exceeds twice the electrocaloric adiabatic temperature change is locally realized, using just the distributed thermal capacitances and resistances and spatio-temporal distributed electric field control. First, simulations demonstrate surface temperature changes up to four times (400%) the electrocaloric adiabatic temperature change for several implementations of all-solid state distributed element configurations. Then, experimentally, an all-solid-state assembly is built from commercial electrocaloric capacitors with two independently-controlled parts, and the measured surface temperature change was 223% of the adiabatic electrocaloric temperature change, which clearly exceeds twice the adiabatic temperature change and verifies the practical feasibility of the approach. This allows a significant increase of the maximum temperature difference per stage in cascaded and thermal switch-based electrocaloric heat pumps, which was previously limited by the adiabatic electrocaloric temperature change (100%) under no-load conditions. Distributed thermal element simulations provide insight in the spatio-temporal temperatures within the all-solid-state electrocaloric element. Since only the distributed thermal capacitance and resistance is used to boost the temperature change, the maximum absolute temperature change occurs only in parts of the all-solid-state element, for example close to the surfaces. A trade-off of the approach is that the required electrocaloric capacitance increases more than the gained boost of the absolute temperature change, reducing the power density and electrical efficiency in heat pump systems. Nevertheless, the proposed approach enables to simplify electrocaloric heat pumps or to increasing the achievable temperature span, and might also improve other electrocaloric applications.

Local Temperature Reduction in Thin Wire Cables Due to Contacted Thermocouples

Complex cable systems for various applications need to be protected from over-current-induced high temperatures. That is why the cable temperature has to be monitored. Temperature measurement especially in thin wire cables can be challenging. Many measurement approaches only allow the surface temperature measurement and therefore are not appropriate for monitoring the inner cable temperature. Others, such as the widespread thermocouple temperature measurement, can relevantly change the cable temperature and therefore lead to deviations between the measured temperature and the real cable temperature without connected measurement equipment. This effect is studied in this article. For comparison, an indirect temperature measurement approach is presented that is based on the cable’s resistance measurement. Subsequently, the temperature drop due to a connected thermocouple is measured. An analytical model for the description of this effect is proposed and validated. Finally, based on parameter studies, a rule for selecting suitable thermocouples is derived.

On the use of inline phase transformation sensors in a hot strip mill: case studies

Dynamic cooling control process on the run-out table (ROT) in a hot strip mill (HSM) is an important step to achieve the hot-rolled steel product quality required by customers. The measurements of strip temperature and the amount of transformed phase on the ROT are complementary to each other for the tracking of the material state of the strip during the cooling process. Infrared pyrometers have been widely used for the measurement of strip temperatures, while commercial systems for inline measurement of steel’s phase transformation only became available in recent years. Since 2015, a Transformation Monitor sensor system using EMSpec Technology has been deployed on the ROT of the HSM#2 at Tata Steel in the Netherlands for inline measurement of phase transformation. This paper presents use case studies of the Transformation Monitor. It will demonstrate the advantages of in-situ real time measurement of phase transformation, not only to reveal the internal microstructure of steel strips but also to measure the evolution of transformation–time trajectory on the run-out cooling table, as a complimentary measurement to pyrometer-based surface temperature measurement.

Experimental study and numerical simulation of a floor heating system in a three-dimensional model: Parametric study and improvement

In recent years, the installation of underfloor heating systems has increased considerably in many countries, due to their ability to be connected to a solar thermal collector in order to benefit from clean and renewable energy. This promising technology allows for reduced energy consumption, achieves a higher level of comfort, and ensures a more homogeneous temperature distribution than conventional heating systems. A huge loophole is detected in research works concerning the three-dimensional numerical modelling of the thermal behavior of underfloor heating by COMSOL Multiphysics software. The present study aims to reduce these knowledge gaps and to analyze the thermal behavior of the direct solar floor numerically and experimentally under the specific climatic conditions of Casablanca, Morocco. Visualize the thermal behavior of the underfloor heating system and the heating circuit as a 3D model using COMSOL Multiphysics software, based on the finite element method by investigating the influence of various design and operational parameters to select the best parameters that guarantee thermal comfort in the case of installing this heating system in traditional bathrooms.The results obtained by numerical simulation are then compared with those of the experimental measurements in order to verify the validity of the numerical model. The average deviation between the simulated and measured surface temperatures is approximately 1.04%, while the deviation in pipe temperature is around 3.13%, which shows a very good agreement between the numerical and experimental results. In addition, the results of the parametric study indicate that the key elements for enhancing the floor heating system are primarily a floor covered by tile with a minimum thickness of 5 mm, a pipe spacing of approximately 15 cm, a PER pipe diameter of 16/20 mm, and a thermal insulation layer with a thickness of 50 mm made of XPS or polystyrene. The incorporation of these improvements in the standard model ensures a surface temperature within the thermal comfort range of a less warm bathroom, approximately 34.13 °C, and a high heat flux emitted at the surface around 502.07 W compared to the standard model. In the literature, it was found that the comparison of architectural characteristics of direct solar floors receives minimal attention, with most studies only comparing systems in terms of thermal comfort or energy efficiency. In this study, the analysis and interpretation of the results obtained can be used to help engineers and designers select the type and dimensions of the best materials for heating floors installed in traditional bathrooms in Morocco.

Contact Temperature Measurements on Hybrid Aluminum–Steel Workpieces in a Cross-Wedge Rolling Process

The Collaborative Research Center 1153 is investigating a novel process chain for manufacturing high-performance hybrid components. The combination of aluminum and steel can reduce the weight of components and lead to lower fuel consumption. During the welding of aluminum and steel, a brittle intermetallic phase is formed that reduces the service life of the component. After welding, the workpiece is heated inhomogeneously and hot-formed in a cross-wedge rolling process. Since the intermetallic phase grows depending on the temperature during hot forming, temperature control is of great importance. In this paper, the possibility of process-integrated contact temperature measurement with thin-film sensors is investigated. For this purpose, the initial temperature distribution after induction heating of the workpiece is determined. Subsequently, cross-wedge rolling is carried out, and the data of the thin-film sensors are compared to the temperature measurements after heating. It is shown that thin-film sensors inserted into the tool are capable of measuring surface temperatures even at a contact time of 0.041 s. The new process monitoring of the temperature makes it possible to develop a better understanding of the process as well as to further optimize the temperature distribution. In the long term, knowledge of the temperatures in the different materials also makes it possible to derive quality characteristics as well as insights into the causes of possible process errors (e.g., fracture of the joining zone).

Contributions towards variable temperature shielding for compact NMR instruments.

The application of compact NMR instruments to hot flowing samples or exothermically reacting mixtures is limited by the temperature sensitivity of permanent magnets. Typically, such temperature effects directly influence the achievable magnetic field homogeneity and hence measurement quality. The internal-temperature control loop of the magnet and instruments is not designed for such temperature compensation. Passive insulation is restricted by the small dimensions within the magnet borehole. Here, we present a design approach for active heat shielding with the aim of variable temperature control of NMR samples for benchtop NMR instruments using a compressed airstream which is variable in flow and temperature. Based on the system identification and surface temperature measurements through thermography, a model predictive control was set up to minimise any disturbance effect on the permanent magnet from the probe or sample temperature. This methodology will facilitate the application of variable-temperature shielding and, therefore, extend the application of compact NMR instruments to flowing sample temperatures that differ from the magnet 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.

Tactile Sensor Structure Optimized for Sliding Motion With High Resolution Recording of Surface Topography

The demand for tactile devices with human-like exquisiteness has recently been increasing in various fields. Among the various parameters that humans feel through the tactile system, temperature and surface topography are the most important parameters to achieve artificial tactile devices with human level precision. Here, we present a new tactile sensor with high resolution surface topography recording and temperature measurement. Our tactile sensor was designed to have a surface topography sensing part driven by P(VDF-TrFE) and a thermistor part for temperature sensing. Even though the sensor touched the same temperature object, the sliding condition showed different resistance change values. Therefore, the correlation factors of the sliding velocity to temperature were defined with a simple relation function. To achieve high resolution recording, ‘zig-zag’ arrayed tactile sensor can overcome the limitations of simple matrix cell design. The design eliminates empty spaces between sensor cells. By using these systems, a resolution of ~500μm to x-direction was achieved. This tactile sensor has linear sensitivity to pressure with a superior response time of 10ms for dynamic sensing. By integrating the dynamic piezoelectric signals during the sliding motion, we can reconstruct the surface topography of various objects.

Real-time monitoring of focused ultrasound therapy using intelligence-based thermography: A feasibility study

Focused ultrasound (FUS) therapy has been widely studied for breast cancer treatment due to its potential as a fully non-invasive method to improve cosmetic and oncologic results. However, real-time imaging and monitoring of the therapeutic ultrasound delivered to the target area remain challenges for precision breast cancer therapy. The main objective of this study is to propose and evaluate a novel intelligence-based thermography (IT) method that can monitor and control FUS treatment using thermal imaging with the fusion of artificial intelligence (AI) and advanced heat transfer modeling. In the proposed method, a thermal camera is integrated into FUS system for thermal imaging of the breast surface, and an AI model is employed for the inverse analysis of the surface thermal monitoring, thereby estimating the features of the focal region. This paper presents experimental and computational studies conducted to assess the feasibility and efficiency of IT-guided FUS (ITgFUS). Tissue phantoms, designed to mimic the properties of breast tissue, were used in the experiments to investigate detectability and the impact of temperature rise at the focal region on the tissue surface. Additionally, an AI computational analysis employing an artificial neural network (ANN) and FUS simulation was carried out to provide a quantitative estimation of the temperature rise at the focal region. This estimation was based on the observed temperature profile on the breast model's surface. The results proved that the effects of temperature rise at the focused area could be detected by the thermal images acquired with thermography. Moreover, it was demonstrated that the AI analysis of the surface temperature measurement could result in near real-time monitoring of FUS by quantitative estimation of the temporal and spatial temperature rise profiles at the focal region.

NEW FUNCTIONALITIES OF THE WEIGH-IN-MOTION SYSTEM: iWIM SOLUTION

This paper presents new functionalities for systems weighing vehicles in motion, which result from the integration of various measurement technologies and the use of a precise registration and data processing system. The utilized registration track provides accurate measurements of basic vehicle parameters such as axle load and vehicle speed and makes it possible to determine the location of the vehicle passing the weighing station, calculate the width of the tire tread, and detect twin (double) wheels. A key functionality is the assessment of the reliability of the measurement, taking into account, among other factors, vehicle movement dynamics and the ambient conditions during the measurements. For this purpose, additional measurements of road surface temperature and wind speed and direction were introduced. The technological solutions used and the proprietary data processing algorithms are described. Tests carried out to verify the effectiveness of the proposed algorithms and to assess the significance of the influence of the isolated factors permitted confirmation of the validity of the proposed solutions.

New publication of the VDI/VDE guideline 3520 “Surface temperature measurement with contact thermometers” – contents and background of the development

Abstract. Temperature measurement at the surface of solids by means of contact thermometers has its own metrological characteristics, which are in contrast to characteristics of the measurement with immersed contact thermometers. They significantly influence the accuracy and the measurement uncertainty of the measured temperature and its deviations. Up to now, no national or international guideline exists which deals with the determination of the static and dynamic measurement deviations. Therefore, the guideline committee “VDI/VDE-GMA FA 4.62 Contact Thermometry” has developed the new VDI (Association of German Engineers) and VDE (Association for Electrical, Electronic and Information Technologies) guideline 3520 “Surface temperature measurement with contact thermometers”. It contains information about the most important properties of contact surface thermometers and error sources, and it presents typical measurement results for various applications. In addition, the parameters influencing the measurement result and test equipment for their determination are described, and concrete examples of thermometer data sheets are given.