Plane Source Method Research Articles

Comparison of uniform and piecewise-uniform heatings when estimating thermal properties of high-conductivity materials

A d-optimum criterion is applied to the three-layer apparatus used for simultaneously estimating thermal properties (for example, thermal conductivity and effusivity) through the plane source method. The objective is to perform a comparison between uniform heating and piecewise-uniform heating of high-conductivity solid samples. In particular, the latter case is modeled through a two-dimensional heat conduction problem in which a rectangular plate (i.e. the sample) is partially heated at the front boundary through a surface heat flux, while all the other boundaries are kept insulated. The optimal experiment is designed for different set-ups of the experimental apparatus (width of the heated region, number of sensors and their locations). The convergence and the computational efficiency of the estimation iterative procedure are the terms of the comparison, as well as the expected standard deviations of thermal conductivity and effusivity. The results indicate that the use of a piecewise-uniform heating is not completely beneficial for isotropic materials. In fact, if on one hand it may offer standard deviations reduced up to about 40%, on the other hand it would require an experiment about six times longer than that required by a uniform heating to ensure a good convergence of the estimation iterative procedure. Therefore, a major computational effort is required.

MTPS Analytical Temperature and Heat Flux Solution With Thermal Contact Resistance

Abstract An exact transient analytical solution of the temperature fields and heat fluxes for the modified transient plane source (MTPS) method is presented. The MTPS sensor is made of a thin disk with a heater/sensor and a heated guard ring on its surface, providing a one-dimensional heat flow to a semi-infinite sample in contact with its surface. The MTPS sensor measures the thermal effusivity of the sample. Two different solutions are derived, one is in the form of an infinite series with no thermal resistance, and the other is in integral form and includes thermal resistance between the MTPS sensor surface and the measured sample. The theoretical model is supplemented by experimental results.

Determination of Thermal Parameters of Concrete by Active Thermographic Measurements

The knowledge of the thermal parameters of a particular concrete is essential for thermal design of a building, but also could help to identify and assess the state of a concrete structure. Active thermography has the potential to be applied onsite and to provide a fast investigation of thermal properties. In this work, three different concrete samples were investigated by active thermography in reflection and in transmission setup. It was found that this method yields the same results without direct contact as the Transient Plane Source (TPS) method as an established inspection tool.

Thermal and Acoustic Properties of Agar Phantom Fabricated from Agar Powder

We present in this paper, step by step procedure in obtaining Agar Phantom from Agar Powder and degassed water using specified bioinstruments, therewith subsequently demonstrate by the Step - Wise Transient Method (STM), how the manufactured (TMM) was utilized in identifying the thermal, and acoustic properties of the fabricated material. TMMs are materials which mimic human body tissues, and as human body tissues are not readily easy to come by, Agar Agar has been used for fabrication of this suitable alternative to simulate the properties of human body tissues in certain medium. Keywords: Phantom, Transducer, Agar, Ultrasound, Step - wise Transient Plane Source (STPS) Method. DOI: 10.7176/ISDE/12-1-05 Publication date: March 31 st 2021

On the Optimum Experiment and Heating Times when Estimating Thermal Properties through the Plane Source Method

The objective of the current research work is to provide the optimum experiment and heating times in dimensionless form to be used for the simultaneous estimation of thermal properties when running a plane source-based experiment. In detail, they are thermal conductivity, volumetric heat capacity and contact resistance. These optimum times are limited to high-conductivity materials and are obtained by using a D-optimum criterion for different values of the heater heat capacity and contact resistance. These two parameters (that actually are not of interest) come from the use of a novel mathematical modeling of the plane source apparatus. It is based on a boundary condition of the sixth kind applied to the sample to adequately describe the heat diffusion between the heater and the same specimen. Then, for an experimental ease-of-use, the optimum experiment and heating times are given in a graphical form as a function of the heater heat capacity with the contact resistance as a parameter. Correlations fitting the graphical results are also provided. A numerically simulated measurement shows the use of these graphics.

Embarked Quad Flat Nonlead 16, 32, and 64 Electronic Devices Subjected to Free Convection: Influence of the Adhesive Paste on the Junction Temperature

The junction temperature of the quad flat nonlead (QFN) electronic devices equipping embarked assemblies may be controlled so that it does not exceed the maximum value recommended by the manufacturer. The packaging design is then important to ensure correct operation and high reliability, given the significant power generated during operation and the inclination angle of the packages during the flight. It is particularly important when thermoregulation is achieved by means of natural convection. The objective of this study is to examine the influence of the adhesive paste used to connect the Die of the QFN with its base. The study deals with three devices among the most used in the conventional arrangements: the QFN16, 32, and 64. A three-dimensional (3D) numerical solution based on the control volume formulation allows to determine their thermal behavior for generated power ranging from 0.1 to 1.0 W by steps of 0.1 W and inclination angle varying between 0 deg (horizontal position) and 90 deg (vertical position) by steps of 15 deg. A wide range of the paste’s thermal conductivity has been considered, varying between −80% and +100% of its average value, measured by means of the transient plane source (TPS) method. The numerical results confirmed by measurements show that the junction temperature strongly increases when the conductivity of the paste decreases. The temperature is moderately reduced when the paste is thermally more conductive. Relationships are proposed to calculate the junction temperature for the three considered devices, according to the generated power, the inclination angle, and the relative paste’s thermal conductivity.

Temperature Solution for Transient Heat Conduction in a Thin Bilayer Between Semi-Infinite Media in Thermal Effusivity Measurement

A series expansion and an approximation have been derived for the temperature in the general case of transient heat conduction in two thin layers between two semi-infinite media at different uniform initial temperatures. The temperature accuracy and thermal effusivity measurement accuracy have been mapped to establish a window of operation for direct thermal effusivity measurement by the modified transient plane source (MTPS) method. The presented temperature series enables quick thermal analysis of thermally thick and semithick samples without factory correction/calibration.

Thermal conductivity of powders used in continuous casting of steel

Measurements of the thermal conductivity (λ) and thermal diffusivity (α) have been carried out on samples of Na2O·SiO2 and four mould slags for temperatures between 295 and 1300 K. These measurements were carried out using the transient plane source (TPS) method (295–373 K) and the transient hot wire (THW) technique (295–1300 K) and the laser pulse (LP) or laser flash method in the case of Na2O·SiO2 Values of λ295 were very similar (1.07±0.03 W m−1 K−1) and all samples exhibited a maximum at the critical temperature (Tcrit = 1040±10 K) beyond which there was a sharp drop in λTHW with increasing temperature. Measurements were also carried out on semi-crystalline samples with increasing λ and fraction of crystalline phase. These samples also exhibited a sharp drop in the thermal conductivity for temperatures above Tcrit and λTcrit was found to be 1.6±0.05 W m−1 K−1. Thermal conductivity (λLP) values calculated from reported thermal diffusivity (αLP) values were in very good agreement with the measured λTHW values for temperatures between 295 K and Tcrit but λLP values did not decrease with increasing temperature above Tcrit (cf. λTHW). Consequently, it was found that λLP≈7λTHW for mould slags.

A new PET resolution measurement method through Monte-Carlo simulations.

The aim of this study was to propose a novel method for image quality assessment in PET scanners through estimation of the modulation transfer function (MTF) of a plane source. The simulation was implemented using the previously validated Monte-Carlo model. A comparison of the proposed method with the more traditional technique, based on a line source, was also performed. The Geant4 application for tomographic emission (GATE) Monte-Carlo package was used for model development, and reconstructed images were obtained using software for tomographic image reconstruction (STIR) with cluster computing. A novel plane source consisting of a radioactive ((18)F-fluorodeoxyglucose) thin-layer chromatography plate was simulated (total source activity: 44.4 MBq) to assess image quality through the MTF. All images were reconstructed with the three-dimensional filtered back projection (FBP3DRP) and ordered-subsets expectation maximization (OSEM) reprojection algorithms. The MTFs obtained using ordered-subsets expectation maximization show, in all cases, that higher frequencies are preserved compared with those obtained using the FBP3DRP. In addition, the plane source method is less prone to noise than the conventional line source method (SD=0.0031 and 0.0203, respectively). The thin-layer chromatography-based plane source presented requires materials commonly found in a clinical environment and could be used to assess image quality in nuclear medicine departments and to further develop PET and single-photon emission computed tomography scanners through Monte-Carlo simulations.

Thermal and Tribological Properties of Phenolic/CNT-Alumina Hybrid Composites

Carbon nanotube (CNT) reinforced polymer composites are of great interest, because their superior properties can produce composite materials with high strength, light weight, and multifunctional features. In this work, the thermal and tribological properties (wear) of Phenolic/CNT-Alumina Hybrid composites were studied. The CNT-alumina hybrid (chemically hybrid) was produced via Chemical Vapour Deposition (CVD). The Phenolic/CNT-Alumina Hybrid composites were fabricated using hot mounting moulding. The tribological properties were monitored using a Ducom TR-20 pin-on-disk tester, under dry sliding conditions. The thermal conductivity was measured using the Transient Plane Source (TPS) method, using a Hot-DiskTM Thermal Constant Analyzer. The results show that CNT-Alumina hybrid enhanced the thermal and tribological properties of the polymer composites.

Evaluation of Effective Thermal Conductivity for Mineral Cast Structural Materials Using Steady-State and Transient Methods

Abstract Thermal conductivity is a thermophysical property that represents the rate at which heat energy can be transported through the material. For any alternate material chosen for machine tool structures, the study of its thermal characteristics is imminent. Thermal conductivity is one major characteristic to be analysed. Mineral cast structures made of epoxy-granite are found to exhibit good mechanical properties, such as high stiffness and damping ratio. The material also has lesser weight, compared to conventional materials used for machine tool structures. Hence, these materials are emerging as an alternate to conventional cast iron machine tool structures. This study attempts to determine the effective thermal conductivity of epoxy granite material using steady-state and transient plane source (TPS) methods. The results obtained using the experimental methods are compared with geometrical models and the suitability of the methods is evaluated. It is observed that both methods are suitable for measuring effective thermal conductivity of two-phase materials. Compared to TPS method, the steady-state method is a slow and material-consuming technique but provides more accurate results. The effective thermal conductivity of the developed material is compared with some commercial polymer composites and observed that the developed material has greater thermal conductivity.

Influence of CdS Nano Additives on the Thermal Conductivity of Poly(vinyl chloride)/CdS Nanocomposites

PVC/CdS nanocomposites have been prepared by solution casting method taking 2, 4, 6 and 8 wt% of CdS nanoparticles. PVC/CdS nanocomposites were characterized through TEM measurement. The measurement of effective thermal conductivity of PVC/CdS nanocomposites has also been done using transient plane source (TPS) method. The effects of concentration of CdS nanoparticles and temperature on the effective thermal conductivity of polymer PVC/CdS nanocomposites have been studied. The variation of effective thermal conductivity with the concentration of filler particles and temperature has also been discussed in terms of dispersion of filler particles into polymer matrix and phonon scattering mechanism, respectively.

Thermal and Mechanical Behavior of Polymer Nano-composite

This paper presents the results on thermal transport and mechanical properties of CdS/ PMMA nano-composites prepared by solution casting method at different concentrations of nano-particles in the composites. Thermal conductivity was determined using Transient Plane Source (TPS) method at room as well as elevated temperatures. The measurement of thermal conductivity of CdS/PMMA nano-composites at room as well as elevated temperatures shows an increasing trend upto glass transition temperature, beyond which it shows a constant value. This peculiarity in the increase of thermal conductivity of CdS/PMMA nanocomposites is explained through the presence of CdS in PMMA matrix. Mechanical properties of these nano-composites have been studied using Dynamic Mechanical Analyzer (DMA). The increase in elastic properties in the CdS nano-particles embedded PMMA as compared to pure PMMA is explained on the basis of interaction between CdS and polymer and decrease in free volume of PMMA in the composite. The results on these measurements show that 6 wt. % of CdS nano-particles in PMMA matrix provides higher values of thermal conductivity and elastic properties, which is a critical composition.

Dynamic Measurements of the Temperature Coefficient of Resistance in the Transient Plane Source Sensor

The extended dynamic plane source (EDPS) method is one of the transient methods for measurements of the thermal conductivity and thermal diffusivity in solids. This technique uses a transient plane source (TPS) sensor, which serves as the heat source and thermometer. Its calibration consists of measuring the temperature dependence of the TPS sensor resistance and computing the temperature coefficient of resistance (TCR) using least-squares (LS) estimation. The goal of this study is to calibrate the TPS sensor directly in the apparatus for the EDPS method. The article presents an uncertainty assessment of the TCR measurement. The main sources of uncertainty stem from resistance measurements of the constant resistor and platinum thermometer calibration. The LS estimate of the TCR in a nickel TPS sensor is 4.83 × 10−3 K−1 at 20 °C and 4.57 × 10−3 K−1 at 45 °C with a combined standard uncertainty better than 0.04 × 10−3 K−1, which is 0.7 %.

Thermal Conductivity of Ceramic Fibres at High-Temperatures

Three ceramic fibres VK-60, ABK and Nextel/VK-80 produced by the steam blowing and nozzle dissemination methods have been investigated for the effect of press load per unit area and temperatures using the advantageous transient plane source (ATPS) method in air. It was noticed that, with the increase of the aluminium content in the composition of the ceramic fibres, the thermal conductivity of the material decreases and the isolation properties improved. The Nextel/VK-80 fibre has the lowest and VK-60 the highest value of thermal conductivity at room temperature. The application of a press load results in an increase in the value of the thermal conductivity for all the fibres analysed. ABK fibres showed the least increase and Nextel/VK-80 registered an increase of about 10% in the value of thermal conductivity within the load increase from 0.6 to 6.6 kN m−2. However, above 6.6 kN m−2 the thermal conductivity of all the samples increased almost linearly. The thermal conductivity measurements as a function of temperature indicated the same trend for an increase in thermal conductivity for all the samples.

An investigation of factors affecting detector and geometric correction in normalization of 3-D PET data

Normalization in three-dimensional (3-D) positron emission tomography (PET) comprises two aspects: correction for differential detector response and correction for geometric effects. Comparison of rotating rod source and uniform cylinder data suggests that the position of the source used to correct for sensitivity should be similar to that of the emission data. A plane source method has been devised that uses a moving line source that traverses the transaxial field-of-view, emulating a plane source, but without the problems associated with using a conventional plane source in 3-D (uniformity, scatter, cost, etc.). This device has been used to record high count density acquisitions for direct normalization of emission data and also to examine geometric effects with increasing azimuthal (/spl phi/) and polar (/spl theta/) angles in the 3 D data set. The data have confirmed observations of two distinct geometric patterns seen previously in two-dimensional PET: an overall transaxial sensitivity profile that decreases toward the center of the projection and a crystal interference profile that changes with position in the block. Correction for the first geometric component removes a low-sensitivity hole in 3-D PET reconstructions, and correction for the second component removes ring artifacts. The direct normalization approach produces an artifact along the central axis of the scanner. A quantitative index of nonuniformity for 1-pixel-thick annular regions of interest showed a reduction from 60% nonuniformity with no corrections to less than 15% when the plant source data were used to directly normalize the emission data. The moving line source provides high quality data and may be an appropriate normalization device for 3-D PET.

Leaching studies of137Cs from ion-exchange resin incorporated in cement or bitumen

Leaching of137Cs from ion-exchange resin incorporated in cement and bitumen composite using two methods based on theoretical equations has been developed. These were: Method I, diffusion equation derived for a plane source model1 and Method II, empirical model employing a polynominal equation2,3. Results presented in this paper are examples of data obtained in a cement and bitumen testing project which will influence the design of a future radioactive waste storage center.

A Non-Steady-State Method of Measuring the Thermal Conductivity of Transparent Liquids

A plane source method has been developed for non-steady-state measurements of the thermal conductivity of transparent liquids. The plane source is realized by using an electrically heated metal foil, suspended in the liquid. The temperature distribution is described by using the concept of instantaneous heat sources giving a simple expression of the optical path, which is recorded with wave-front-shearing interferometry. The thermal diffusivity is determined simply by measuring the positions of the fringes, locating the points where the gradient of the optical path is constant and knowing the times between two subsequent exposures. The accuracy of the method, which is an absolute one, is demonstrated. The average deviation from the recommended values of the thermal conductivity was found to be 0.37%.