Measured Temperature Difference Research Articles

Data-driven simulation-assisted-Physics learned AI (DPAI) for heat diffusion in large grain polycrystalline materials

In this paper, we propose Data-driven simulation-assisted Physics-learned Artificial Intelligence (DPAI), a deep-learning algorithm to simulate heat diffusion in large-grain polycrystalline materials. The DPAI model captures the spatio-temporal representation of heat diffusion in the material from input sequences from the training dataset. The training dataset consists of various temperature plots of polycrystalline materials taken from Finite Element (FE) simulations having varying numbers of grains oriented in random directions with a single-point heat source at the center. The arbitrary plane of the 3D microstructure of these materials is represented using 2D Voronoi tessellations. Voronoi configurations are used to model the geometry of the 2D Computer-Aided Design (CAD) model. Each cell of the Voronoi tessellation represents one grain of the microstructure. This CAD model is used as an input to the FE for solving heat diffusion equations. To model the near-realistic material anisotropy and accurately measure temperature differences at cell boundaries, a smaller mesh size is required in FE modeling, which takes considerable solver time. Therefore, the proposed Deep learning model significantly reduces the computational time while maintaining accuracy as compared to conventional numerical techniques. After training, the effectiveness of the trained DPAI model is examined by modeling larger domain problems involving a greater number of grains and varying material properties. The simulation result is qualitatively compared with the experiment. A scaled-up version of the microstructure is represented using Unidirectional Carbon Fiber laminate. The laminate is heated with a point heat source and the temperature plots are captured using Infrared Camera.

Quantitative correlation between temperature difference and sintering neck length in material extrusion-based additive manufacturing

The performance of polymeric parts fabricated via material extrusion-based additive manufacturing (MEAM) is significantly influenced by the sintering neck length between filaments. Despite its importance, elucidating the underlying mechanism governing the formation of inter-filament sintering necks is challenging due to the difficulties in monitoring temperature fields during MEAM. In this work, the thermal condition in MEAM was simplified using a printer with a tubular hotbed, coupled with a high temporal-spatial resolution infrared (IR) camera to monitor temperature field variations during printing. An advanced IR image processing method, integrating multi-directional retrieval and whole-loop average filtering, was developed to accurately measure temperature differences between filaments. By correlating these measurements with micro-CT characterizations, a quantitative relationship between temperature difference and sintering neck length was established. Through single- or multi-loop defect experiments, microscopic defect detection and analysis were conducted, achieving the prediction of sintering neck length variations at a 10 μm level with an 85 % accuracy. This work is believed to provide potential value for further accurate prediction of the mechanical properties of MEAM parts.

Comparison of cooling grey solutions in the sense-city urban demonstrator for adapting cities to heat waves

SummaryFaced with the increase in urban heat in summer, cities must quickly adapt by offering cool islands. If nature-based solutions are efficient and popular, other so-called grey solutions exist and can also provide solutions. In this paper we compare standard grey solutions in Sense-city, an urban demonstrator equipped with sensor, located in the scientific campus of Cité Descartes at Marne la Vallée. Our objective is on the one hand to compare the effectiveness of standard solutions over time, but also to study the ability of sense-city and its canyon street to study this phenomenon despite its relatively small size. MethodsIn this work we follow an experimental approach using a wide coverage of calibrated sensors deployed in Sense-city. We have conducted two measurement campaigns in July 2021 and July–August 2022 where we study the effectiveness of standard solutions (shading, white floor surface, street watering) to reduce the air temperature in the canyon street of sense-city. As the days are different, we compare the temperature difference in the street canyon equipped with these cooling solutions with that on the surrounding area. This method allows us to overcome daily variations. To interpret the results, we analyse the shades and we follow the temperature over time and not only during the hottest hours. We also calculate the UTCI (Universal Thermal Climate Index) to compare the perceived temperature. FindingsThe results show that despite its small size, the canyon street of sense-city behaves like a canyon street and that the measured temperature differences due to heat exchanges comply with physical laws and that the number and spatial distribution of sensors is validated. The Sense-city demonstrator can therefore be used to carry out thermal efficiency experiments. In addition, the method we used to compare cooling solutions allows us to limit the impacts due to slight daily variations. Finally, while watering is effective in rapidly lowering the temperature in the street, shading remains an optimal solution for the perceived temperature, even if it would be ideal to close them at the end of the day to allow air circulation.

Applicability and evaluation of airtightness prediction method using pressure differences under actual climate conditions

The blower door test and tracer gas test methods are commonly used to measure airtightness and infiltration in buildings. Nonetheless, these methods can be costly and time-consuming. To address these issues, the air pressure measurement and prediction system (APMPS) was proposed. This method predicts the airtightness of a building by measuring the differential pressure across its components. However, the effectiveness of this method has yet to be verified under various conditions. The aim of this study is to analyze the effectiveness of the APMPS under different building and weather conditions. Three residential buildings of varying heights were analyzed, and measurement of differential pressure and temperature differences were taken. The actual airtightness was determined using blower door tests, and the results were compared to the predicted airtightness calculated by the APMPS. The results indicate that APMPS is effective in predicting building airtightness, with the majority of predicted values falling within the range of 2-3 h−1 at 50 Pa. The accuracy of the predictions improved as the building height, differences in indoor and outdoor temperatures, and differential pressure increased. Furthermore, a significant correlation was observed between the error rate, height difference, and differential pressure at a significance level of 1%. The APMPS has demonstrated its value as reliable tool for accurately predicting the airtightness of multi-story buildings under various conditions. This method simplifies the measurement of airtightness in building components, which is crucial for evaluating building energy demand and air quality.

Two-phase heat transfer microchannel system identification with Particle Swarm Optimization (PSO) approach

The complex behavior of two-phase flow particularly in microchannels can be unpredictable. Experimental measurements are near impossible because of the unavailable compatible assessment equipment. Meanwhile, repeated experiments for reliability of outcomes are costly and involved much time and effort. Environmentally friendly propane is currently being considered as a replacement for hazardous coolants in available refrigeration and air-conditioning systems. This paper reports a system identification (SI) analysis of the collected experimental data of two-phase flow of refrigerant R290 in a microchannel test rig. An ARX model was chosen as the dynamic model, and the modeling of the input–output data was done using a new methodology based on particle swarm optimization (PSO) technique. Measured temperature difference across the microchannel test section and the mass flow rate were the input and output, respectively. The performance of the particle swarm optimization with discoverer (PSOd) was investigated and compared to the original PSO technique. The model was then validated by mean-squared error (MSE). Results demonstrate the advantages of discoverer in PSOd over its standard counterpart with a smaller MSE of 6.2629 × 10−11 and a faster convergence. The SI allows a better prediction of the mass flow rate before any further experiments to obtain the heat transfer coefficient are done. The model provides better management of design of experiments that involve the complex two-phase flow in a microchannel, consequently saving experimental time and cost.

Design and performance evaluation of a novel thin-film heat flux sensor

Thin-film heat flux sensor is suitable for the harsh environment in aerospace application. To further improve the accuracy of testing and to realize the measurement in two directions, this work proposes a new design of the thin-film heat flux sensor. Based on the numerical simulation method, this work investigates the influence of geometric parameters, physical property and working conditions on the sensor test error, and analyzes the testing performances under steady and transient states. Results indicate that the sensor test error is mainly related to the thermal resistance ratio of the sensor in the measurement system. The accuracy of the thin-film heat flux sensor increases with the increase of sensor size or local total thermal resistance. Besides, the newly designed sensor has satisfying steady and transient characteristics, including the small time constant, fast response, and good linear relationship between the measured temperature difference and the surface heat flux.

Spatially resolved investigation of flame particle interaction in a two dimensional model packed bed

This study investigates the interaction between a premixed methane-air flame and particles inside a model packed bed. The opacity of the spherical packed beds to visible light poses a major barrier to the implementation of highly resolved optical diagnostics, so that no detailed experimental data were so far available for the validation of numerical simulation. Here, a two-dimensional cylindrical packed bed design is set up, which enables direct line-of-sight optical measurements without loss of spatial resolution over the fluid region between the particles. In this study, the case of cold metallic cylindrical particles (T = 377 K) relevant to start-up of a reactor is investigated using internal particle cooling, which also allows cylinder specific heat transfer rate measurements by differential temperature measurements on the coolant streams. The two dimensional assumption is first verified by measuring the inflow velocity and cylinder temperature profile along the cylinders. Chemiluminescence imaging is then performed using a telecentric lens to observe the position and geometry of the two-dimensional flame front with respect to the surrounding cylinders without loss of resolution. Simultaneously, the cylinder-specific flame to cylinder heat transfer rates and cylinder surface temperature are measured. As the flame is closely surrounded by the three cooled cylinders, intense heat transfer is observed in this region corresponding to 25 ± 2.5% of the flame thermal power. Flames were stabilised at different positions depending on inflow velocity and equivalence ratio, and a direct correlation between flame to cylinder stand-off distance and the heat transfer rate normalised to the flame thermal power was found for both top and side cylinders. Also, sidewall quenching distances to the curved cylinder surfaces were evaluated, and seem to be influenced by the presence of a warm recirculation zone behind the cylinders. This investigation provides fully resolved flame front position and heat transfer rates for a known geometry and cylinder thermal boundary conditions, and provides validation data for numerical simulations of this high flame particle coupling case.

Organization and evolution of climate responsive strategies, used in Turpan vernacular buildings in arid region of China

Under the global crisis of energy shortage and environmental pollution, the climate responsive strategies used in vernacular buildings have attracted much attention for their potential to reduce energy consumption and carbon emissions. However, the relationships between these traditional climatic strategies were not precisely perceived, which may cause the inapplicability of these strategies for contemporary rural houses. In this paper, taking the Turpan vernacular buildings in arid region of China, the climate responsive strategies of buildings in the most significant periods such as the Gaochang period (before 1318), the Khanate and Republican period (1318–1949), the Modern period (1949–2010), and the Contemporary period (2011–present) were summarized. In addition, two different types of climatic strategies organizations, namely multilayer spaces and integrated building envelopes, were identified based on the temperature difference measurement and comparative analysis. The assessment of thermal performance of the organizations was conducted by the methodology of software simulation. Furthermore, the applicability of the organizations in rural areas was discussed, and a new combined organization was proposed. Consequently, this study can contribute to provide the main approaches for climatically responsive rural houses.

Apparatus for measurement of thermoelectric properties of a single leg under large temperature differences.

Thermoelectric (TE) devices operate under large temperature differences, but material property measurements are typically accomplished under small temperature differences. Because of the issues associated with forming proper contact between the test sample and the electrodes and the control of heat flux, there are very few reports on large temperature difference measurements. Therefore, practically relevant performance parameters of a device, namely, power output and efficiency, are estimated by temperature averaging of material properties, whose accuracy is rarely validated by experimental investigations. To overcome these issues, we report an apparatus that has been designed and assembled to measure the TE properties-Seebeck coefficient, electrical conductivity, thermal conductivity, and power output and efficiency of a single thermoelectric material sample over large temperature gradients. The sample holder-a unique feature of this design-lowers the contact resistance between the sample and the electrodes, allowing for more accurate estimates of the sample's properties. Measurements were performed under constant temperature differences ranging from 50 to 300K with the hot side reaching 673K on a metallized Mg2Si0.3Sn0.7 leg synthesized in the laboratory. To simulate practical operating conditions of a continuously loaded generator, continuous current flow measurements were also performed under large temperature differences. The temperature-averaged TE properties from standard low temperature difference measurements and the experimental TE properties agree with each other, indicating that the designed setup is reliable for measuring various thermoelectric generator properties of single TE legs when subjected to temperature gradients between 50 and 300K.

Projected parameters of air in the classroom and their impact on the human body

AbstractThe air temperature in school buildings significantly affects the ability of students and teachers to focus on the educational process. Students usually begin to feel an increase the temperature in room. The purpose of this study is to find the limit of the temperature rise in the classroom when people no longer feel the temperature rise in the room. For this reason, several experimental measurements of indoor air parameters were carried out: air temperature, relative humidity and carbon dioxide concentration. Measured temperature differences and individual subjective ratings of audiences determined the dependence using mathematical statistics, from which can be determined the critical level of increase in air temperature at which people no longer perceive the change in air temperature.

Extrapolation method for reliable measurement of Seebeck coefficient of organic thin films

Measurement of the Seebeck coefficient of an organic thermoelectric (TE) thin film necessitates the accurate measurement of the temperature difference across the film. However, direct measurement of temperature difference is difficult for a small-gap organic TE device, which is favored for the high-resistance organic materials. Here, the effect of a nonlinear temperature distribution on the Seebeck coefficient measurement of organic TE films was systematically investigated to enable clear identification of the Seebeck coefficient for an organic TE film. The nonlinear temperature distribution across an organic TE device was analyzed by a finite-element analysis simulation and IR thermal imaging. The nonlinear temperature distribution resulted in a difference between the measured temperature difference and the actual temperature difference across the organic TE film. The conventional interpolation method significantly overestimated the Seebeck coefficient when the temperature distribution was nonlinear. To reduce the measurement error, the ideal Seebeck voltage was extrapolated from a series of Seebeck voltages measured at different position in the edge-contacted device configuration. The ideal Seebeck coefficients of various organic TE films with a wide range of electrical conductivities were determined successfully, and the Seebeck coefficient measured by extrapolation method was not affected by the geometry of the organic TE film. • Nonlinear temperature distribution during Seebeck coefficient measurement is systematically investigated. • An extrapolation method is used for evaluating an ideal Seebeck voltage that directly corresponded to the temperature difference across organic films. • Our method enables accurate measurement of the Seebeck coefficient of an organic thin film with a short-channel architecture and a high-resistance.

Concealed multiscale feature extraction network for automatic four-bar target detection in infrared imaging

The measurement of the minimum temperature difference (MTD) at which a four-bar target can be resolved is an important task for assessing the performance of infrared imaging equipment. Recently, there have been efforts to use an automatic objective approach based on machine learning to replace the classical manual subjective MTD measurement approach, which is heavily influenced by the psychological subjective factors of the operator and is limited in accuracy and processing speed. However, the scale variability of the four-bar targets and the high intrinsic target-background similarity in infrared images have been observed to present a challenging problem for automatic MTD measurement. We present a concealed multiscale feature extraction network (CMF-Net), a backbone for automatic multiscale four-bar target detections, in an attempt to address the aforementioned challenges. We first propose a multilevel feature pyramid module to construct a robust representation of multiscale four-bar targets. Next, to distinguish between the four-bar targets from the background, a target saliency enhancement module (TSE) is introduced to capture discriminative features about the target by encoding local and global contextual information. Experiments show that the proposed method is effective and achieves state-of-the-art four-bar target detection results on infrared-image dataset compared with existing methods.

A monolithic three-dimensional thermal convective acoustic vector sensor with acoustic-transparent heat sink.

An acoustic vector sensor can directly detect acoustic particle velocity based on the measured temperature difference between closely spaced heated wires. For the detection of velocity in three dimensions, an integrated three-dimensional (3 D) sensor is desired, but it remains challenging in MEMS (Micro-Electro-Mechanical System) manufacturing. Here, a novel monolithic 3 D acoustic vector sensor is proposed, which is constructed using in-plane distributed wires assembled with acoustically transparent heat sink. The planar MEMS structure of the proposed sensor makes it easy to be fabricated and packaged. This work offers a new method for the design of acoustic vector sensors and other thermal convection-based MEMS sensors.

Using Fiber Bragg Grating Sensors to Quantify Temperature Non‐Uniformities in Plasmonic Catalyst Beds under Illumination

AbstractDistinguishing between photothermal and non‐thermal contributions is essential in plasmon catalysis. Use of a tailored optical temperature sensor based on fiber Bragg gratings enabled us to obtain an accurate temperature map of an illuminated plasmonic catalyst bed with high spatiotemporal resolution. Its importance for quantification of the photothermal and non‐thermal contributions to plasmon catalysis is demonstrated using a Ru/Al2O3 catalyst. Upon illumination with LEDs, we measured temperature differences exceeding 50 °C in the top 0.5 mm of the catalyst bed. Furthermore, we discovered differences between the surface temperature and the temperature obtained via conventional thermocouple measurements underneath the catalyst bed exceeding 200 °C at 2.6 W cm−2 light intensity. This demonstrates that accurate multi‐point temperature measurements are a prerequisite for a correct interpretation of catalysis results of light‐powered chemical reactions obtained with plasmonic catalysts.

Complex thermal analysis of supercapacitor by thermal impedance spectroscopy

Thermal impedance spectroscopy (TIS) measurement was developed for thermal analysis of supercapacitors. Compared with previously reported TIS measurement methods, the specific heat flux path through the supercapacitor device can be manipulated under the experimental system equipped with cold and heat sources. Using complex notation, the thermal impedance was defined as the ratio of the measured temperature difference across the tested device to the imposed heat flux. Different from the performance of Li-ion batteries, the thermal impedance spectra of the tested supercapacitor showed two semicircles with different diameters. The negative real part of the thermal impedance in the high frequency region could be considered as a frequencyrelated phase delay caused by the time response of the thermocouples in the temperature measurement. In addition, heat capacities and thermal resistances of the active materials and the casing of the tested supercapacitor were derived by equivalent thermal RC circuit. Furthermore, the effect of environmental humidity on the thermal characterization of active materials was isolated from the thermal impedance spectra.

INVESTIGATION OF THE UNCERTAINTY VALUE AT MEASURING THE TEMPERATURE OF THE COOLANT IN THE PIPELINES WITH OUTSIDE SURFACE MOUNTED TEMPERATURE SENSORS

During performing technological and production processes and monitoring the modes of their operation, the problem of determining the temperature of various media transported through pipelines is solved without incut temperature sensors (TS) in them, i.e. with using outside surface mounted TS (SMTS). This method is allowing to measure mechanical values at technological processes without structure broken and without influence to physicochemical properties of measured media.
 Using of SMTS possible to register heat losses on sections of heating mains, pollution degree of pipelines internal walls, to control serviceability of measurement channels of temperature of the coolant in heat meters, etc.
 In the article authors presents results of research the uncertainty values for measuring of the coolant temperature in heating systems pipelines under different modes of its flow. First of all, the uncertainty value of the measurements results was estimated, which was determined by the results of the study for the calculation model and field tests at existing district heating systems.
 Emphasis is paid on estimating the difference between the registration of temperature in the middle of the pipeline, determined by mortise transducers and the temperature measured by outside surface mounted temperature transducers, taking into account the temperature gradient across the pipeline and the quality of its insulation.
 It is determined that: the temperature measured by temperature transducers on the surface of the pipeline at different points of its perimeter, with proper installation and sufficient thermal insulation does not depend on their location; the average temperature on the surface of the pipeline, measured using the developed method of installation of PT, slightly differs (ΔT ≈- 0.3⁰C) from the average temperature of the coolant in the middle of the flow; temperature transducers have high reproducibility of measurements and small difference in readings between channels at parallel measurements (»0,03⁰С).
 It is substantiated that high metrological performances of temperature transducers allow to use them for solving other tasks: measuring the distribution of heat fluxes in heating systems of residential buildings to perform hydraulic balancing of heating systems and increase their efficiency; estimate of contamination of pipelines and heat exchange equipment to determine the need for their washing; determination of thermal resistance of buildings protective structures to assess their energy efficiency; determination of large pumps efficiency by calorimetric method; checking the correct of operation the temperature measuring channels of heat meters and cold meters; in other technology areas where measurements of small temperature differences with high accuracy are required.

Improving coal/gangue recognition efficiency based on liquid intervention with infrared imager at low emissivity

Accurate recognition of coal and gangue is the core technology to realize intelligence in fully mechanized top coal caving mining. The influence of emissivity of the thermal imager on the efficiency of the coal/gangue recognition is considered in this paper. The temperature of coal and gangue are measured by the infrared thermal imager with different emissivity. The results show that: compared with high emissivity, low emissivity conditon can enlarge the measured temperature difference between coal and gangue, which will improve the recognition efficiency greatly. The maximum temperature difference reaches 4.5°C–4.8°C in liquid intervention experiment with low emissivity (ε = 0.1–0.3). Setting the emissivity of infrared thermal imager at a low level may be a new approach to widen the temperature difference between coal and gangue, which will improve the recognition efficiency greatly. When ε = 0.3, the maximum temperature difference ratio reaches 9.0, which shows the best potential for improving coal/gangue recognition efficiency with infrared thermal imager at low emissivity.

Temperature difference measurement with using two RTD sensors as example of evaluating uncertainty of a vector output quantity

The evaluation of results in the case of indirect multi-parameter measurements is presented. A theoretical basis for determining the estimates of values, the uncertainties and the correlation coefficients of indirectly obtained multi-measurand is explained in detail. The example of a difference and an average of two-temperature indirect measurement is given with the use of two RTDs. Such sensors are used in the laboratory and industrial temperature control systems. The uncertainty of measurements depends on the errors of two RTDs and the structure of signal conditioning circuit.

Intensity level as sustainable energy: Analysis of the conversion of energy stored on cicadas sound waves

In this study, the researchers measured cicadas' sound waves, considering that cicadas are mostly found in rural areas. The intensity level meter (AMTAST AMF003) was used with time variations (9:00 JST; 12:00 JST; and 15:00 JST). Measurements of air temperature differences (Krisbow Temperature Humidity Data Logger) were also carried out, and weather conditions were also considered in data collection using satellite data from Himawari, Japan. The interpretation results of intensity level's trend measured at 3:00 pm JST were decreased concerning the changes in days. Meanwhile, the measurement at 09:00 am and 12:00 pm JST did not show a decrement concerning the changes in days (31 days in total). These results show that temperature changes (towards autumn) can affect the intensity level of sound waves. In addition, slightly different intensity levels can affect large changes in acoustic power or the produced sound.

Temperature Difference Measurement of Metal Surfaces at Normal Temperatures Under Sunlight by Differential Chromatic Features of Visible Images

The temperature of metal surfaces at normal temperatures under sunlight can be measured by combining visible images with machine learning (ML). But this method is susceptible to illumination conditions, which causes large errors. To solve this problem, a method of temperature difference measurement based on visible images’ differential chromatic features (DCFs) between two metal surfaces, which are at different temperatures but the same illumination, is proposed in this paper. Through experiments, temperature difference image libraries of brass surfaces under varying illumination are established. DCFs of each image are extracted, and temperature difference between two surfaces is used as the label. Models that can predict the temperature difference between two surfaces are trained by ML. Prediction results show that the mean absolute error of this temperature difference measurement method can be as low as 1.6, decreasing by 42% at most compared with those of simply measuring the surface temperature. The effect of temperature and illumination on visible images’ gray levels is analyzed. And it is concluded that the introduction of a temperature-constant surface provides a reference item for illumination, which helps to weaken the influence of illumination changes and filter out the interference caused by them. This is why the prediction accuracy can be improved by the temperature difference measurement method.