Local Temperature Measurements Research Articles

Computational fluid dynamics analysis of the Canadian deuterium uranium moderator tests at the Stern Laboratories Inc.

A numerical calculation with the commercial computational fluid dynamics code CFX-14.0 was conducted for a test facility simulating the Canadian deuterium uranium moderator thermalehydraulics. Two kinds of moderator thermalehydraulic tests at Stern Laboratories Inc. were performed in the full geometric configuration of the Canadian deuterium uranium moderator circulating vessel, which is called a calandria tank, housing a matrix of horizontal rod bundles simulating calandria tubes. The first of these tests is the pressure drop measurement of a cross flow in the horizontal rod bundles. The other is the local temperature measurement on the cross section of the horizontal cylinder vessel simulating the calandria system. In the present study, the full geometric details of the calandria tank are incorporated in the grid generation of the computational domain to which the boundary conditions for each experiment are applied. The numerical solutions are reviewed and compared with the available test data. Copyright © 2015, Published by Elsevier Korea LLC on behalf of Korean Nuclear Society.

Identification of the hygrothermal properties of a building envelope material by the covariance matrix adaptation evolution strategy

This paper proposes the application of the covariance matrix adaptation (CMA) evolution strategy for the identification of building envelope materials hygrothermal properties. All material properties are estimated on the basis of local temperature and relative humidity measurements, by solving the inverse heat and moisture transfer problem. The applicability of the identification procedure is demonstrated in two stages: first, a numerical benchmark is developed and used as to show the potential identification accuracy, justify the choice for a Tikhonov regularization term in the fitness evaluation, and propose a method for its appropriate tuning. Then, the procedure is applied on the basis of experimental measurements from an instrumented test cell, and compared to the experimental characterization of the observed material. Results show that an accurate estimation of all hygrothermal properties of a building material is feasible, if the objective function of the inverse problem is carefully defined.

B123 走査型熱顕微鏡による局所温度計測の研究 : 能動温度計測法における加熱方法の最適化(OS-8:マイクロ・ナノ熱工学(2))

B123 走査型熱顕微鏡による局所温度計測の研究 : 能動温度計測法における加熱方法の最適化(OS-8:マイクロ・ナノ熱工学(2))

Two 27 MHz Simple Inductive Loops, as Hyperthermia Treatment Applicators: Theoretical Analysis and Development.

Background. Deep heating is still the main subject for research in hyperthermia treatment. Aim. The purpose of this study was to develop and analyze a simple loop as a heating applicator. Methods. The performance of two 27 MHz inductive loop antennas as potential applicators in hyperthermia treatment was studied theoretically as well as experimentally in phantoms. Two inductive loop antennas with radii 7 cm and 9 cm were designed, simulated, and constructed. The theoretical analysis was performed by using Green's function and Bessel's function technique. Experiments were performed with phantoms radiated by the aforementioned loop antennas. Results. The specific absorption rate (SAR) distributions were estimated from the respective local phantom temperature measurements. Comparisons of the theoretical, simulation, and experimental studies showed satisfying agreement. The penetration depth was measured theoretically and experimentally in the range of 2–3.5 cm. Conclusion. The theoretical and experimental analysis showed that current loops are efficient in the case where the peripheral heating of spherical tumor formation located at 2–3.5 cm depth is required.

A 15 <formula formulatype="inline"><tex Notation="TeX">$\mu{\rm W}$</tex></formula> 5.5 kS/s Resistive Sensor Readout Circuit with 7.6 ENOB

A low power SAR logic-based resistive sensor readout circuit is proposed. A high sensitivity thermistor is used for local temperature measurements. The need for a low-noise front-end voltage amplifier is avoided by employing time-domain operation. In each operation step the sensor resistance is compared with the value of a reference resistive DAC which is implemented on chip. Therefore no stable, temperature compensated reference voltage is needed for operation. Furthermore the chip is operational with supply voltages ranging from 1.2 to 1.8 volts. Detailed analyses of the circuit gain and noise are provided. In addition, the effect of circuit topology on the noise performance is discussed. The effect of 1/f noise on accuracy of the circuit is also negligible due to resetting the charge-integrating capacitor after each comparison. A prototype chip is fabricated in 0.18- μm CMOS. The circuit dissipates 15 μW with 5.5 kS/s conversion rate from a 1.5 V supply. The complete interface circuit has 14 pJ/c-s figure of merit and 7.6 effective number of bits.

Thermal error modelling of machine tools based on ANFIS with fuzzy c-means clustering using a thermal imaging camera

Thermal errors are often quoted as being the largest contributor to CNC machine tool errors, but they can be effectively reduced using error compensation. The performance of a thermal error compensation system depends on the accuracy and robustness of the thermal error model and the quality of the inputs to the model. The location of temperature measurement must provide a representative measurement of the change in temperature that will affect the machine structure. The number of sensors and their locations are not always intuitive and the time required to identify the optimal locations is often prohibitive, resulting in compromise and poor results.In this paper, a new intelligent compensation system for reducing thermal errors of machine tools using data obtained from a thermal imaging camera is introduced. Different groups of key temperature points were identified from thermal images using a novel schema based on a Grey model GM (0,N) and fuzzy c-means (FCM) clustering method. An Adaptive Neuro-Fuzzy Inference System with fuzzy c-means clustering (FCM-ANFIS) was employed to design the thermal prediction model. In order to optimise the approach, a parametric study was carried out by changing the number of inputs and number of membership functions to the FCM-ANFIS model, and comparing the relative robustness of the designs. According to the results, the FCM-ANFIS model with four inputs and six membership functions achieves the best performance in terms of the accuracy of its predictive ability. The residual value of the model is smaller than ±2μm, which represents a 95% reduction in the thermally-induced error on the machine. Finally, the proposed method is shown to compare favourably against an Artificial Neural Network (ANN) model.

Temperature distribution during RF ablation on ex vivo liver tissue: IR measurements and simulations

Radiofrequency thermal ablation is the first therapeutic option for the minimally invasive treatment of liver tumors. This medical procedure employs the Joule heat produced by a RF electromagnetic field to kill tumor cells. The outcome of the procedure is strongly affected by the temperature distribution near the RF applicator, however the measurement of this distribution, even in ex vivo experiments, is not straightforward since most traditional local temperature measurement techniques are not well-suited, due to both electromagnetic interferences and the sensor heat sink effect. Given the importance of the temperature field knowledge, in this paper special care was devoted to its measurement employing both infrared thermal imaging and NTC thermistors. Several RF ablation tests on ex vivo porcine liver tissue were carried out measuring the space–time evolution of temperature during the procedure (with spatial resolution ≤1 mm) and producing useful data for the design and the calibration of a numerical model. Electro-thermal numerical simulations of the experimental tests were performed using a mathematical model suitable for the heating phase of the procedure (up to 95 °C). The simulations results allowed to check the physical consistency of the measured data and suggested that a constant thermal conductivity is satisfactory for modeling the temperature evolution during RF ablation.

Local Nusselt number enhancements in liquid–liquid Taylor flows

Abstract Thermal management has emerged as a critical requirement to ensure the performance and reliability of electronic devices and systems. System level heat fluxes are approaching the limits of conventional forced air cooling, and there is a need to develop alternative cooling techniques for devices such as processors, power amplifiers and laser arrays. This paper examines the potential heat transfer enhancements of a two phase liquid–liquid Taylor flow regime. The primary focus of the work was to examine the influence of slug length and carrier phase variations on the local Nusselt numbers. An experimental facility was designed and commissioned to subject the flow to a constant heat flux boundary condition, a boundary condition commonly encountered in thermal management applications. Local temperature measurements were acquired using a high resolution infrared thermography system. Experiments were carried out over slug length, Capillary and Prandtl numbers that spanned several orders of magnitude in a minichannel geometry. Reductions in carrier slug length and increases in dispersed slug length were found to augment the heat transfer rates, with the greatest enhancements observed in flows with carrier slug lengths approaching the channel diameter. The thickness of the liquid film separating the dispersed slugs from the heated capillary walls was found to play a significant role in the removal of heat, with increases in film thickness resulting in a reduction in the heat transfer rates. Based on the characteristics identified, a novel correlation is proposed to model the flow in the thermally developing and fully-developed regions.

Parameter estimation for energy balance models with memory

We study parameter estimation for one-dimensional energy balance models with memory (EBMMs) given localized and noisy temperature measurements. Our results apply to a wide range of nonlinear, parabolic partial differential equations with integral memory terms. First, we show that a space-dependent parameter can be determined uniquely everywhere in the PDE's domain of definitionD, using only temperature information in a small subdomainE⊂D. This result is valid only when the data correspond to exact measurements of the temperature. We propose a method for estimating a model parameter of the EBMM using more realistic, error-contaminated temperature data derived, for example, from ice cores or marine-sediment cores. Our approach is based on a so-called mechanistic-statistical model that combines a deterministic EBMM with a statistical model of the observation process. Estimating a parameter in this setting is especially challenging, because the observation process induces a strong loss of information. Aside from the noise contained in past temperature measurements, an additional error is induced by the age-dating method, whose accuracy tends to decrease with a sample's remoteness in time. Using a Bayesian approach, we show that obtaining an accurate parameter estimate is still possible in certain cases.

Development of the charge exchange recombination spectroscopy and the beam emission spectroscopy on the EAST tokamak.

Charge eXchange Recombination Spectroscopy (CXRS) and Beam Emission Spectroscopy (BES) diagnostics based on a heating neutral beam have recently been installed on EAST to provide local measurements of ion temperature, velocity, and density. The system design features common light collection optics for CXRS and BES, background channels for the toroidal views, multi-chord viewing sightlines, and high throughput lens-based spectrometers with good signal to noise ratio for high time resolution measurements. Additionally, two spectrometers each has a tunable grating to observe any wavelength of interest are used for the CXRS and one utilizes a fixed-wavelength grating to achieve higher diffraction efficiency for the BES system. A real-time wavelength correction is implemented to achieve a high-accuracy wavelength calibration. Alignment and calibration are performed. Initial performance test results are presented.

Surface charge sensing by altering the phase transition in VO2

Detection of surface charges has various applications in medicine, electronics, biotechnology, etc. The source of surface charge induction may range from simple charge-polarized molecules like water to complicated proteins. It was recently discovered that surface charge accumulation can alter the temperature at which VO2 undergoes a Mott transition. Here, we deposited polar molecules onto the surface of two-terminal thin-film VO2 lateral devices and monitored the joule-heating-driven Mott transition, or conductance switching. We observed that the power required to induce the conductance switching reduced upon treatment with polar molecules and, using in-situ blackbody-emission direct measurement of local temperature, we show that this reduction in power was accompanied by reduction in the Mott transition temperature. Further evidence suggested that this effect has specificity to the nature of the species used to induce surface charges. Using x-ray absorption spectroscopy, we also show that there is no detectable change in oxidation state of vanadium or structural phase in the bulk of the 40 nm VO2 thin-film even as the phase transition temperature is reduced by up to 20 K by the polar molecules. The ability to alter the phase transition parameters by depositing polar molecules suggests a potential application in sensing surface charges of different origins and this set of results also highlights interesting aspects of the phase transition in VO2.

Measurement of Local Specimen Temperature under Flowing Gas Ambient in the Environmental Scanning Transmission Electron Microscope (ESTEM) Using Diffraction

Measurement of Local Specimen Temperature under Flowing Gas Ambient in the Environmental Scanning Transmission Electron Microscope (ESTEM) Using Diffraction

Laboratory study of non-aqueous phase liquid and water co-boiling during thermal treatment

In situ thermal treatment technologies, such as electrical resistance heating and thermal conductive heating, use subsurface temperature measurements in addition to the analysis of soil and groundwater samples to monitor remediation performance. One potential indication of non-aqueous phase liquid (NAPL) removal is an increase in temperature following observations of a co-boiling plateau, during which subsurface temperatures remain constant as NAPL and water co-boil. However, observed co-boiling temperatures can be affected by the composition of the NAPL and the proximity of the NAPL to the temperature measurement location. Results of laboratory heating experiments using single-component and multi-component NAPLs showed that local-scale temperature measurements can be mistakenly interpreted as an indication of the end of NAPL–water co-boiling, and that significant NAPL saturations (1% to 9%) remain despite observed increases in temperature. Furthermore, co-boiling of multi-component NAPL results in gradually increasing temperature, rather than a co-boiling plateau. Measurements of gas production can serve as a complementary metric for assessing NAPL removal by providing a larger-scale measurement integrated over multiple smaller-scale NAPL locations. Measurements of the composition of the NAPL condensate can provide ISTT operators with information regarding the progress of NAPL removal for multi-component sources.

Heat transfer mechanisms in isolated bubble boiling of water observed with MEMS sensor

Heat transfer characteristics of isolated bubble saturated pool boiling of water were investigated by local wall temperature measurement using an original micro-electro-mechanical systems (MEMS) sensor and a wall heat transfer evaluation. The measured temperature clearly indicated dynamic heat transfer phenomena below an isolated bubble including microlayer evaporation, dry-out of the microlayer, and rewetting of the dry-out region. Local heat removal due to microlayer evaporation exceeded 1MW/m2. Microlayer evaporation was found to have a central role in the wall heat transfer. The contribution of microlayer evaporation to bubble growth was about 50%, and did not vary significantly with wall superheat. The remaining 50% of the latent heat in the bubble was transferred from the superheated liquid surrounding the bubble. Finally, the spatial distribution of the initial microlayer thickness was calculated from the local heat flux of the wall.

Measurement of local temperature in tapes and bulks by the Double Thickness Method

The average temperature of the heated metal conductor are usually measured by the hot wire method. This method is not applicable to measure the temperature of superconductor. As an alternative we proposed the Double Thickness Method. In DTM two identical elements of superconductor are glued together and miniature thermometer is placed between them. This method allows to measure temperature on superconducting tapes and bulks under the condition of intense cooling (for example, in liquid nitrogen). DTM can be used in AC, DC and pulse heating regimes.

On-line estimation of inlet and outlet composition in catalytic partial oxidation

An estimation strategy is presented for determining inlet and outlet composition of catalytic partial oxidation (CPOX) of methane over rhodium catalyst using simple, fast measurements: temperature, and thermal conductivity. A 1-D high fidelity simulation model for CPOX studied in Ref. [1] for a portable fuel cell application is developed and enhanced for transient experiments. Process dynamics are analysed to demonstrate how solid temperatures along the axes of the reactor reflect the endothermic/exothermic interplay of reactions during a process upset. Model reduction is then used to obtain a low complexity model suitable for use in a moving horizon estimator with update rates faster than 0.02 s. System theoretic observability analysis is then conducted to predict the suitability of different measurement designs and the best locations for temperature measurements for estimating both inlet and outlet gas mole fractions for all species. Finally, a Moving Horizon estimator is implemented and simulation experiments are conducted to verify the accuracy of the estimator.

Vapor-Based Interferometric Measurement of Local Evaporation Rate and Interfacial Temperature of Evaporating Droplets

The local evaporation rate and interfacial temperature are two quintessential characteristics for the study of evaporating droplets. Here, it is shown how one can extract these quantities by measuring the vapor concentration field around the droplet with digital holographic interferometry. As a concrete example, an evaporating freely receding pending droplet of 3M Novec HFE-7000 is analyzed at ambient conditions. The measured vapor cloud is shown to deviate significantly from a pure-diffusion regime calculation, but it compares favorably to a new boundary-layer theory accounting for a buoyancy-induced convection in the gas and the influence upon it of a thermal Marangoni flow. By integration of the measured local evaporation rate over the interface, the global evaporation rate is obtained and validated by a side-view measurement of the droplet shape. Advective effects are found to boost the global evaporation rate by a factor of 4 as compared to the diffusion-limited theory.

A new nonlinear surface heat flux calibration method based on Kirchhoff transformation and rescaling principles

A novel surface heat flux calibration method is presented applicable to nonlinear inverse heat conduction problems. Quasi-linearization of the nonlinear heat equation is achieved by combining the Kirchhoff transform with time-domain rescaling based on the local temperature measurement. At each time step, the thermophysical properties are held constant throughout the spatial domain though allowed to vary with advancing time. The rescaled forms are then resolved through a calibration framework. The proposed calibration formulation is expressed in terms of Volterra integral equation of the first kind. This functional equation relates the rescaled net unknown surface heat flux to the rescaled net calibration surface heat flux and their corresponding rescaled Kirchhoff transformed variables for the in-depth temperature measurements during the calibration test and unknown runs. Tikhonov regularization is introduced for generating a family of predictions based on the Tikhonov parameter. The L-curve strategy is used for selecting the proper regularization parameter. In this paper, favourable numerical results are demonstrated verifying both accuracy and robustness of the rescaling calibration approach in the presence of significant experiment noise. The methodology works well for a variety of practical isotropic materials. This approach does not require knowledge of the probe position but presently requires knowledge of the host material’s thermal diffusivity.

Thermal boundary layer near roughnesses in turbulent Rayleigh-Bénard convection: Flow structure and multistability

We present global heat-transfer and local temperature measurements, in an asymmetric parallelepiped Rayleigh-Bénard cell, in which controlled square-studs roughnesses have been added. A global heat transfer enhancement arises when the thickness of the boundary layer matches the height of the roughnesses. The enhanced regime exhibits an increase of the heat transfer scaling. Local temperature measurements have been carried out in the range of parameters where the enhancement of the global heat transfer is observed. They show that the boundary layer at the top of the square-stub roughness is thinner than the boundary layer of a smooth plate, which accounts for most of the heat-transfer enhancement. We also report multistability at long time scales between two enhanced heat-transfer regimes. The flow structure of both regimes is imaged with background-oriented synthetic Schlieren and reveals intermittent bursts of coherent plumes.

Local Optical Temperature Measurements around Magnetosomes within Single Bacteria to Study Size and Geometry Effects on Heating

Using the temperature sensitive of the fluorescence of GFP, we record the local temperature inside magnetotactic bacteria. These bacteria use magnetosomes - membrane and protein enclosed magnetite crystals - for navigating along the earth magnetic field lines. Upon purification, suspensions of magnetosomes are found to be highly effective heaters while subject to radio frequency magnetic field, yielding larger Specific Absorption Rates (SAR) than most of the common ferrofluids, making magnetosomes ideal candidate for application in magnetic field induced cell stimulation or hyperthermia cancer treatment. In the wild-type bacteria the magnetosomes are aligned in well-ordered chains, but mutants are available with different spatial arrangement or crystal size. We demonstrate that GFP fused to a magnetosome protein MamC may function as a molecular-scale temperature probe, and show that wild type magnetosomes raise the local temperature around the magnetosome membrane significantly, upon application of radio frequency magnetic field. The heating is confined to the vicinity of the magnetosomes, as the mutant strain producing the same magnetosomes but expressing a cytosolic GFP does not show heating of the entire cytosol. This approach enables us to study the effect of different spatial arrangement and nano-crystal size on the RF magnetic field induced heating directly in the individual bacteria, and to screen for more efficiently heating mutations. Finite element simulation is performed to understand the relation between spatial arrangement of magnetosomes and their heating efficiency.