Steady-state Temperature Measurements Research Articles

Ultrahigh-speed absolute temperature sensing using ferroelectric HfO2 enabled by transient negative differential capacitance.

Conventional ferroelectric polarization-driven temperature sensors, like pyroelectric sensors, often face challenges such as slow response times, limited compatibility with conventional nanoelectronics, and inability to operate under constant temperature conditions. These shortcomings hinder their adaptability to a broad range of applications, especially when compared to thermal and optical sensors. To address these challenges, we introduce a proof-of-concept methodology that enables ferroelectric-based pyroelectric sensors to measure absolute temperatures with high accuracy and speed. Specifically, we demonstrate that a perturbation pulse (+0.8 V, duration = 180 ns) can serve as an effective probe for quantifying both absolute and dynamic temperatures across ferroelectric hafnium zirconium oxide (HZO) nanolaminates. The device demonstrates an ultrafast response time of ∼50 nanoseconds, offering one million readings per second and a temperature sensing accuracy comparable to the state-of-the-art temperature sensing accuracy of 1.0 K. The observed performance is attributed to the temperature-dependent change of transient negative differential capacitance and effective ferroelectric polarization of HZO. For potential applications, we successfully integrated the sensor with a commercially available universal serial bus interface, thereby demonstrating real-time temperature monitoring during data transfer and environmental heating activities. Our research significantly broadens the range of applications for pyroelectric sensors for both steady-state and rapid dynamic temperature measurements.

Comparative assessment of transient- and steady-state soil thermal conductivity using a specially designed consolidometer

Precise estimation of soil thermal conductivity is crucial for reliable heat flow analysis in soil. Research indicates variations in soil thermal conductivity values estimated using transient- and steady-state temperature measurements. However, sources of such reported differences cannot be specified with certainty. This paper presents the development of a soil thermal conductivity measurement device that enables simulation of a specified stress condition on soil specimens and estimation of both transient- and steady-state soil thermal conductivity values from different segments of a single test. A series of thermal conductivity tests were performed on seven different soils using the specially-designed test setup. The difference in soil thermal conductivity values obtained from transient- and steady-state responses are compared to those reported in the literature. In contrast to steady-state soil thermal conductivity, results indicate an increase in transient-state soil thermal conductivity beyond a threshold value of the rate of soil temperature increment during the transient-state measurement. Furthermore, empirical relations are suggested to correlate soil thermal conductivity of fine-grained soils with plasticity index, hydraulic conductivity, and coefficient of consolidation.

Influence of spray and combustion processes on piston temperatures and engine heat transfer in a high-output diesel engine

Simultaneous measurements of global engine heat transfer and subsurface piston temperatures were utilized to evaluate the potential of an extended duration combustion event to minimize heat rejection in a diesel engine. The combustion duration was parametrically varied by changing the injector orifice diameter (0.167, 0.196, and 0.230 mm) and fuel injection pressure (110–200 MPa) while exploring three high-output operating conditions. This investigation was limited to a single-pulse injection strategy while holding engine load constant to represent operating points at rated power and peak torque. For a constant combustion phasing, the results suggest the duration of the spray and combustion processes did not greatly influence gross indicated thermal efficiency (ITEg) or global heat transfer from the engine, except for extremely long combustion durations of approximately 50 crank-angle degrees or longer. At the longest combustion durations, there was a negative impact on ITEg and global heat transfer. Analysis of the steady-state piston temperature measurements at constant CA50 revealed two interesting, and opposite, trends: as the combustion duration was increased through a smaller orifice diameter injector, the piston temperatures increased by up to 60°C locally on the bowl rim; in contrast, as the combustion duration was increased through lower injection pressures, the piston temperatures decreased by up to 80°C locally on the bowl rim. CFD simulations coupled with a conjugate heat transfer model of the piston predicted the piston heat flux at the highest load operating condition. The CFD results qualitatively agreed with the piston temperature measurements in supporting the conclusion that orifice diameter had a stronger effect on piston heat flux than injection pressure. Overall, this research provides directional trends to engine designers and calibrators for optimizing the injection parameters for decreased engine heat transfer and managing piston temperatures.

Effect of Pin Fins on Jet Impingement Heat Transfer Over a Rotating Disk

Abstract Many engineering applications consist of rotating components that experience high-heat load. Applications like the gas turbine engine consist of rotating disks and the study of heat transfer over such rotating surfaces is of particular interest. In the case of gas turbines, the disk also needs to be protected from the ingress of hot turbine gases caused by the low-pressure region created due to the radially outward pumping of fluid close to the rotating surface. The present experimental study investigates the effects of introducing pin-fins on heat transfer over surface of a rotating gas-turbine disk. The experiments were conducted at rotational Reynolds numbers (ReR) of 5487–12,803 based on the disk diameter (D) and jet Reynolds numbers (Re) of 5000–18,000 based on the jet diameter. The effects of nozzle to target spacing (z/d=2−6), eccentricity of impingement (ε = 0−0.67), angle of impingement—both toward and away from the center (θi and θo=0 deg−20 deg), and the pin fin height (Hf=3.05 mm−19.05 mm) were studied. Steady-state temperature measurements were taken using thermocouples embedded in the disk close to the target surface, and area average Nusselt number (Nu) was calculated. The results have been compared with those for a smooth aluminum disk of equal dimensions and without any pin-fins. The average Nu was significantly enhanced by the presence of pin-fins. The enhancement was higher for lower values of Re, and the maximum enhancement was found to be 3.9 times that of a smooth disk for Re=5000. In the impingement dominant regime, the effect of disk rotation was minimal for a smooth disk, but the heat transfer increased with rotational speed in case of pin-fins. There was no impact of eccentricity on Nu for ε = 0 and 0.33. For ε = 0.67, the maximum reduction in enhancement over a smooth surface (21.95%) was observed when compared with coaxial impingement for stationary impingement for Re=18,000 and z/d=4. The effect of inclination angle was insignificant, and no clear trend could be established. Higher heat transfer rates were observed for z/d=6 with the increasing Re, and this effect diminished with the increase in the rotational speed. With the increase in pin-fin height, especially at higher values of Re, there was in increase in the value of Nu. Qualitative visualization of flow field has been performed for smooth and the pin-fin case using the commercial simulation package Ansys Fluent to further understand the flow features that result in the heat transfer enhancement.

A Well Temperature Correction Based on the Least Squares Method and its Application in a Coal Mining Area, China

With the increase in mining depth of coal resources, high-temperature thermal damage has become increasingly prominent, and research on geotemperature in mining areas has received increasing attention. At present, simple temperature measurement is the most commonly used well temperature measurement method, but the obtained data cannot be used directly and need to be corrected. According to the thermal recovery law of an approximately steady-state hole, the “three-point” method is often used to correct simple well temperature data. However, the calibration work is complicated, time-consuming and laborious. Moreover, in the “three-point” method, the well depth and the time from when the well fluid stopping circulation to the temperature measurement (TSC) are not considered enough, which easily leads to deviations in the well temperature correction results. Based on the TSC and well depth, a simple well temperature correction equation was obtained by using 50 available data points with TSCs less than 20 h of approximate steady-state temperature measurements collected in the Huainan coalfield (TSC < 20 h in the general simple temperature measurements). The fitting effect of the equation was verified with the original ground temperature and geothermal gradient; in its application to the Huainan coalfield geothermal field, the model has achieved an ideal effect.

Geothermal distribution characteristics and sedimentary basin geothermal system in the severe cold region of Northeast China

In this study, Shengli fault depression, Tangyuan fault basin, and northern Songliao Basin in Yitong-Yilan fault zone of Heilongjiang province are considered the research areas for geothermal anomaly. Based on the temperature of the deep thermal reservoir, the hydrothermal fluid channel, caprock thickness, and the mode of heat transfer, which are the main factors controlling the geothermal reservoir formation, we examined geothermal resource system of the underground HDR in this area. First, we inversed the aeromagnetic data, calculated the Curie isotherm depth, analyzed the geothermal distribution characteristics, and estimated the temperature of the deep heat source. Second, we applied the controlled source audio frequency magnetotelluric (CSAMT) and magnetotelluric (MT) methods to obtain the deep electrical structure of the study area. We determined the thickness of the caprock and the hydrothermal fluid channel. Finally, we obtained the borehole geothermal steady-state temperature measurement data and water sample chemical analysis data from the logging temperature curves of 24 wells to infer the mode of heat transfer. Based on the results, we built a model of the geothermal system of the sedimentary basin in this area. The results show that the depth of Curie isotherm in the study area is 17–39 km. The resistivity of sedimentary caprock in the north of Songliao basin is low, and there exists a deep heat source, which is mainly thermal convection. In contrast, in Shengli and Tangyuan fault basins, heat conduction is dominant. Based on the geothermal system model, we conclude that the area from Daqing to Lindian in Songliao basin has a thermal-convection-dominated sedimentary basin geothermal system. Heat exchange is realized by the upwelling of mantle-derived thermal materials through fracture channels. The thick sedimentary caprock reduces the heat loss. It can be a target for sustainable development and utilization of HDR.

The use of Design of Experiments for steady-state and transient inverse melanoma detection problems

Melanoma is one of the most fatal skin cancers; for this reason, there is a need for the development of new safe, non-invasive and efficient diagnostic techniques. Dynamic thermography is showing to be a promising technique for the early detection of skin cancers. Therefore, this paper investigates two different inverse bioheat problems using steady-state and transient skin temperature measurements. Both problems are investigated numerically to estimate how accurate blood perfusion rate, metabolic heat generation, diameter and thickness of the tumour can be estimated simultaneously under exact and noisy measurement data, based on a complex numerical model describing multilayer tissue. The inverse problems have been tested using different melanoma size, Clark II and Clark IV. The Design of Experiments (DOE) technique has been used to solve and analyse the inverse problems. A substantial number of numerical model evaluations, totalling 2,306,486 simulations, had to be undertaken as part of the full factorial DOE. The results show that it is always possible to obtain tumour parameters using exact static or dynamic measurement data. However, for noisy temperature data, the use of a dynamic approach showed an advantage over the steady-state one, which failed because of the very small temperature differences between the healthy skin and the tumour. The dynamic thermography can retrieve blood perfusion rate, thickness and diameter of the tumour as well as the metabolic heat generation despite the low sensitivity for low and high levels of measurement error; however, to detect melanoma lesions at an early stage, the measurement and model errors should be kept as low as possible.

Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

Memory test system for piston steady-state temperature measurement

Regarding the high thermal load of piston in engines, a novel apparatus, memory test system (MTS), was designed for steady-state temperature measurement of piston. By heating MTS up to 100°C and 120°C respectively, a test was carried out to verify the system and measure its error. Considering poor working conditions in engine, the readings of MTS and thermal plugs were compared with each other through an engine test to confirm the reliability of MTS. Moreover, MTS was used to measure piston temperature under multiple working conditions. The results show that MTS has very high precision and reliability and is competent in multi-condition test. MTS is an effective tool to measure piston temperature.

Steady-state and transient microscale temperature measurements by multispectral method and photons counting

This work presents steady-state and transient microscale temperature measurements by optical and multispectral method in the ultraviolet-visible wavelengths. Regarding the classic laws of radiative heat transfers, the photon counting is preferred to the energy measurement. The photonic emission is a random phenomenon and is here measured with statistical laws such as the Gaussian law. The spectral dependence of the optical apparatus transfer function is taken into account by a linear function and the temperature is estimated by inversion with a Levenberg–Marquardt algorithm. Measurements are performed with a small-dimension blackbody developed in the laboratory and with a Chromel wire. Both of them are capable of heating up above 1000 °C. The diameters of the observed surfaces are 10 µm and 5 µm, respectively. The theoretical criterion of wavelength selection and least-squares parameter estimation allow for a difference between the estimated and controlled temperatures lower than 4%.

Inverse method for estimating shear stress in machining

An inverse method is presented for estimating shear stress in the work material in the region of chip–tool contact along the rake face of the tool during orthogonal machining. The method is motivated by a model of heat generation in the chip, which is based on a two-zone contact model for friction along the rake face, and an estimate of the steady-state flow of heat into the cutting tool. Given an experimentally determined discrete set of steady-state temperature measurements along the rake face of the tool, it is shown how to estimate the corresponding shear stress distribution on the rake face, even when no friction model is specified.

Thermal characterization and modeling of ultra-thin silicon chips

Manufacturing ultra-thin chip is an emerging field in semiconductor technology that is driven by 3-D integrated circuits and flexible electronics. Unlike bulk silicon (Si) chips with thickness greater than 400μm, the thermal management of ultra-thin Si chips with thickness smaller than 20μm is challenging due to the increased lateral thermal resistance implying stringent cooling requirements. Therefore, a reasonable prediction of temperature gradients in such chips is necessary. In this work, a thermal chip is implemented in an ultra-thin 0.5μm CMOS technology to be employed in surface steady-state and transient temperature measurement. Test chips are either packaged in a Pin Grid Array (PGA) ceramic package or attached to a flexible polyimide substrate. The experimental results show an on-chip temperature gradient of ∼15°C for a dissipated power of 0.4W in the case of the PGA package and ∼30°C for the polyimide substrate. The time constants are ∼50s and ∼1s for the PGA and the polyimide packages respectively. The measurements are complemented by FEM simulations using ANSYS 14.5 workbench and spice simulations using an equivalent lumped-component thermal circuit model. The lumped-element thermal circuit model is then used for the surface temperature prediction, which is compared to measurement results.

Reduction of Heat Emission to Surroundings from Improved Wood Burning Stove

Apart from emissions and inefficiency, heat generation from wood stoves to the surroundings is another undesirable effect causing health repercussions especially in the small dwellings of tropical regions. The present research addresses this problem. Steady state temperature measurements on the surface of the improved wood burning stove is used to determine this loss in which chimney draft control plays an important role. Experimental results were in good agreement with that of the model simulated using the commercial computational fluid dynamics code. A modified model in which changes were introduced to reduce the radiation and convection losses from the stove to the surrounding regions was simulated. Firstly, the radiation losses from the fire was reduced by reducing the size of fuel supply port. Secondly, a waste heat recovery system was introduced which resulted in lower stove body temperature. This was done by optimizing the use of the draft produced by the chimney.Results of the modified model of the stove showed a reduction of this loss by 12.08%. Stoves currently used under the national project for rural energy development was used for this purpose. Apart from improving the stove efficiency, this development will have a positive impact on the acceptability of the improved wood stove in rural households and also help to further reduce fuel consumption. key words: Heat emission, Chimney optimization, Wood burning stove, Efficiency enhancement and Waste heat recovery.

Use of temperature for diagnosing mixing in the IsaMill

This paper describes a methodology to monitor axial mixing in an IsaMill as a function of mill feed flow rate, mill tip speed and media load. Steady state temperature measurements (profiles) along the mill length were used to quantify the degree of mixing during the comminution process. Combined mass and energy balances across the mill length were done to develop a predictive model for slurry mixing in the mill. The temperature measurements can be used for IsaMill control and optimisation.

Thermal modeling of a cylindrical LiFePO 4/graphite lithium-ion battery

A lumped-parameter thermal model of a cylindrical LiFePO 4/graphite lithium-ion battery is developed. Heat transfer coefficients and heat capacity are determined from simultaneous measurements of the surface temperature and the internal temperature of the battery while applying 2 Hz current pulses of different magnitudes. For internal temperature measurements, a thermocouple is introduced into the battery under inert atmosphere. Heat transfer coefficients (thermal resistances in the model) inside and outside the battery are obtained from thermal steady state temperature measurements, whereas the heat capacity (thermal capacitance in the model) is determined from the transient part. The accuracy of the estimation of internal temperature from surface temperature measurements using the model is validated on current-pulse experiments and a complete charge/discharge of the battery and is within 1.5 ° C. Furthermore, the model allows for simulating the internal temperature directly from the measured current and voltage of the battery. The model is simple enough to be implemented in battery management systems for electric vehicles.

Experimental Investigation of Miniature Three-Dimensional Flat-Plate Oscillating Heat Pipe

An experimental investigation on the effects of condenser temperatures, heating modes, and heat inputs on a miniature three-dimensional (3D) flat-plate oscillating heat pipe (FP-OHP) was conducted visually and thermally. The 3D FP-OHP was charged with acetone at a filling ratio of 0.80, had dimensions of 101.60×63.50×2.54 mm3, possessed 30 total turns, and had square channels on both sides of the device with a hydraulic diameter of 0.762 mm. Unlike traditional flat-plate designs, this new three-dimensional compact design allows for multiple heating arrangements and higher heat fluxes. Transient and steady-state temperature measurements were collected at various heat inputs, and the activation/start-up of the OHP was clearly observed for both bottom and side heating modes during reception of its excitation power for this miniature 3D FP-OHP. The neutron imaging technology was simultaneously employed to observe the internal working fluid flow for all tests directly through the copper wall. The activation was accompanied with a pronounced temperature field relaxation and the onset of chaotic thermal oscillations occurring with the same general oscillatory pattern at locations all around the 3D FP-OHP. Qualitative and quantitative analysis of these thermal oscillations, along with the presentation of the average temperature difference and thermal resistance, for all experimental conditions are provided. The novelty of the three-dimensional OHP design is its ability to still produce the oscillating motions of liquid plugs and vapor bubbles and, more importantly, its ability to remove higher heat fluxes.

Artefacts in intracavitary temperature measurements during regional hyperthermia

For adequate hyperthermia treatments, reliable temperature information during treatment is essential. During regional hyperthermia, temperature information is preferably obtained non-invasively from intracavitary or intraluminal measurements to avoid implant risks for the patient. However, for intracavitary or intraluminal thermometry optimal tissue contact is less natural as for invasive thermometry. In this study, the reliability of intraluminal/intracavitary measurements was examined in phantom experiments and in a numerical model for various extents of thermal contact between thermometry and the surroundings. Both thermocouple probes and fibre optic probes were investigated. Temperature rises after a 30 s power pulse of the 70 MHz AMC-4 hyperthermia system were measured in a tissue-equivalent phantom using a multisensor thermocouple probe placed centrally in a hollow tube. The tube was filled with (1) air, (2) distilled water or (3) saline solution that mimics the properties of tissue, simulating situations with (1) bad thermal contact and no power dissipation in the tube, (2) good thermal contact but no power dissipation or (3) good thermal contact and tissue representative power dissipation. For numerical simulations, a cylindrical symmetric model of a thermocouple probe or a fibre optic probe in a cavity was developed. The cavity was modelled as air, distilled water or saline solution. A generalised E-Field distribution was assumed, resulting in a power deposition. With this power deposition, the temperature rise after a 30 s power pulse was calculated. When thermal contact was bad (1), both phantom measurements and simulations with a thermocouple probe showed very high temperature rises (>0.5 °C), which are artefacts due to self-heating of the thermocouple probe, since no power is dissipated in air. Simulations with a fibre optic probe showed almost no temperature rise when the cavity was filled with air. When thermal contact was good, but no power was dissipated in the tube (2), artefacts due to self-heating were not significant and the observed temperature rises were very low (∼0–0.1 °C). For the situation, with tissue representative power dissipation (3), a temperature rise of ∼0.23 °C was observed for both measurements and simulations. A clinical example of a regional hyperthermia treatment of a patient with a cervix uteri carcinoma showed that the artefacts observed in the case of bad thermal contact also affect the steady-state temperature measurements. Good tissue contact must be assured for reliable intraluminal or intracavitary measurements.

The transient transpiration heat flux meter

A new heat flux measurement principle, based on the transient response of a transpiration radiometer, is proposed. The measurement principle of current transpiration radiometers is based on a steady-state temperature measurement in a porous element. Since it may typically take several seconds to reach these conditions, there are obvious benefits in reducing the instrument response time. This can be achieved through the analysis of its transient response in order to predict the incident heat flux. In addition, the proposed methodology enables the separate measurement of the radiative and convective components of incident heat fluxes, without compromising the known advantages of transpiration radiometers. The availability of such an instrument may enable the development of advanced monitoring, diagnostic and control systems for thermal equipment.

Temperature and pressure field in the Tertiary succession of the western Qaidam basin, northeast Qinghai-Tibet Plateau, China

Based on pressure and temperature data, a comprehensive analysis was carried out for the pressure and temperature regimes in four Tertiary formations of the western Qaidam basin, northeast Qinghai-Tibet plateau. The pressure data were obtained from well pressure tests and the temperature data from systematic steady-state temperature measurements in 10 wells, temperature tests in over 200 wells and calculation for 60 theoretical calculated points. In general, the geothermal gradient in the four Oligocene–Pliocene formations decreases with depth. The Pliocene Upper Youshashan Formation has the highest gradient of 33 °C/km. The Miocene–Oligocene Upper and Lower Ganchaigou Formations have lower gradients of 25–27.5 °C/km in most areas but also several lower gradients down to 20 °C/km. Abnormally high pressures were found at depths of 2650–4350 m, beneath the regional seal in the western Qaidam basin. The abnormal high-pressure is mainly confined to the Lower Ganchaigou Formation with a pressure coefficient up to 1.9. Most parts of the Pliocene Upper and Lower Youshashan Formations are in normal and low abnormal high pressure ( r<1.3) conditions. The relationship between temperature and pressure, together with the areal variation of total salinity values (TSV) of formation water, provide the evidence of the different characteristics of reservoirs distributed in the Tertiary succession. The thermal gradient increases with the pressure coefficient in the Pliocene. The areal variation of TSV, corresponding to the pressure regime, and the dispersed distribution in the histogram of the TSV of formation water indicates that the chemical environment of fluid flows in these strata varies widely. This wide variation implies that the Pliocene succession, with relative low abnormal high pressure values, acts as a vertically open system in the petroleum system. The reservoirs distribution in the Pliocene are isolated distributed and do not correlate with the pressure coefficient. However, the thermal gradient decreases with an increase in the pressure coefficient in the Oligocene Lower Ganchaigou Formation, and its constant TSV of 15–21×10 4 mg/l indicates the formation was in a closed chemical environment of fluid flows over the majority of geological time. The reservoirs in this formation all occur in an abnormally high-pressure zone with a pressure coefficient of more than 1.5.

Development of a Passively Cooled, Electrically Heated Hydride (PACE) Bed

ABSTRACTA nominal 1500 STP-L PAssively Cooled, Electrically heated hydride (PACE) Bed has been developed and tested. The bed contained 12.6 kg of a La-Ni-Al alloy and used aluminum foam to improve heat transfer within the bed. Steady-state temperature measurements made at constant power showed a nonuniform bed temperature profile. Protium absorption rates were measured at pressures of 253 kPa, 413 kPa, and 680 kPa with forced convection cooling air flow rates ranging from 50 to 150 SLPM air. Absorption tests were also performed simulating the absorption of tritium and a method for estimating this rate using protium absorption data presented. Desorption rates were measured at pressures ranging from 20 kPa to 933 kPa using dual and single 400 watt electric heaters and found desorption rates were only impacted at the beginning and the end of a desorption cycle by the use of a single heater.