Measurements Of Thermal Parameters Research Articles

Spatially resolved measurements of thermal parameters in colloidal suspensions in liquid crystals

We report on spatially resolved measurements with a spatial resolution of about 0.1 mm of the transition temperature and of the behavior of the heat capacity, thermal conductivity, and thermal diffusivity over the smectic A–nematic and nematic–isotropic phase transitions in an inhomogeneous aerosil dispersed 8CB liquid crystal. The results were obtained by means of a recently implemented photopyroelectric setup which combines the capability for high temperature resolution measurements with the possibility of visual access in the sample. It is shown that the results relative to different local concentration of particles are consistent with the ones obtained previously on homogeneous samples with different average particle concentration. Finally, the analysis of the local thermal conductivity values has led to an approximate estimate of the local particle concentration in the sample.

Mechanical, Hygric and Thermal Properties of Flue Gas Desulfurization Gypsum

The reference measurements of basic mechanical, thermal and hygric parameters of hardened flue gas desulfurization gypsum are carried out. Moisture diffusivity, water vapor diffusion coefficient, thermal conductivity, volumetric heat capacity and linear thermal expansion coefficient are determined with the primary aim of comparison with data obtained for various types of modified gypsum in the future.

Analysis of glass fiber reinforced cement composites and their thermal and hygric material parameters

Methods of thermal analysis are employed in a study of the high-temperature properties of three different types of glass fiber reinforced cement composites together with the measurements of their thermal and hygric parameters. First, basic TG and DTG measurements are carried out to get the first insight into the high-temperature behavior of the analyzed materials. Then, mercury porosimetry and scanning electron microscopy of specimens subjected to the temperatures of 600 and 800°C are performed and compared to the reference specimens not exposed to any thermal load. Finally, measurements of thermal and hygric parameters of the studied materials are done and matched with the results of the material characterization experiments. Three main effects are found to influence the thermal and hygric properties of the analyzed materials. The first is the decomposition of the cement matrix, which is clearly a negative factor. The second is the positive effect of the presence of fibers that could partially keep the cement matrix together even after significant decomposition of cement hydration products. The third important factor affecting the thermal and hygric properties is the composition of the particular materials. The application of vermiculite aggregates instead of sand is found to be clearly positive because of its porous character leading to the bulk density decrease without worsening the other properties. Also, wollastonite aggregates are a better choice than sand because of its fibrous character that could partially magnify the effect of fiber reinforcement.

A virtual instrumentation system for measurements on the tallest medieval bell tower in europe

A complex virtual instrumentation-based system for measurements of mechanical and thermal parameters of an ancient masonry bell tower is described in this paper. The main focus is oriented toward the measurement issues and the data acquisition and on-line analysis system, which is entirely based on a virtual instrument approach. Choice of transducers and strategies of data acquisition, analyses, and storing are illustrated, and some of the results shown.

Determination of thermal diffusivity using the critical angle in thermal wave reflection at an interface

Reflection and refraction of a plane thermal wave of oblique incidence at an interface is considered theoretically. The thermal wave is generated by an instantaneous plane heat source inclined at a certain angle to the interface. The Green functions for the reflected and transmitted waves are obtained by satisfying boundary conditions. It is shown that the reflection coefficient exhibits a sharp maximum when the angle of incidence coincides with a critical angle. This property can be used for measurements of thermal parameters of two media in thermal contact.

Uncertainty analysis for temperature prediction of biological bodies subject to randomly spatial heating

An analytical solution to the Pennes bioheat transfer equation in three-dimensional geometry with practical hyperthermia boundary conditions and random heating was obtained in this paper. Uncertainties for the predicted temperatures of tissues due to approximate parameters were studied based on analyzing one-dimensional heat transfer in the biological bodies subject to a spatially decay heating. Contributions from each of the thermal parameters such as heat conductivity, blood perfusion rate, and metabolic rate of the tissues, the scattering coefficient and the surface power flux of the heating apparatus were compared and the uncertainty limit for temperature distribution in this case was estimated. The results are useful in a variety of clinical hyperthermia and biological thermal parameter measurement.

Dynamic thermal sensor - principles in MEMS for fluid characterization

Using thin-film technology with its characteristic low masses and high aspect ratios a new range of possibilities is made available for the use of dynamic thermal measuring principles. Based on this, a micromachined sensor was developed for the measurement of transient thermal signal responses leading to the thermal characterization of fluids at low sample volumes. The achieved resolution allowed the measurement of thermal parameters of the investigated fluids, i.e., thermal conductivity and specific heat, inside microfluidic systems at a high sensitivity, enabling the detection of inter-fluid boundaries, e.g., as found in micromixers and -reactors, making the sensor a useful tool for micro fluidic system characterization. This is achieved via the measurement of the frequency dependent thermal signal response.

Energy Recovery from Liquid Wastes of a Sewage-Treatment Plant

The process of combustion of the briquettes produced from compost of liquid wastes originating from a municipal sewage-treatment plant as a substitute or supplement for fossil fuel is presented. The experiments were carried out in a laboratory-scale combustion chamber which simulated a fixed-grate boiler. The laboratory stand was equipped with apparatus enabling measurement of thermal parameters of the combustion process, as well as emission into the atmosphere of various components such as fly ash, nitrogen oxide, carbon oxide, sulfur dioxide, and heavy metals. It was established that the briquettes can be used as fuel and that similar combustion and thermal conditions to combustion of brown coal were achieved with an essential benefit of lower air pollution.

Thermal shock behaviour of industrial carbon anodes

Thermal shock resistance of industrial carbon anodes was studied from both the direct thermal shock test and indirect measurements of thermal shock resistance parameters derived from thermal and mechanical properties. The direct thermal shock test was conducted using the so-called arc discharge technique. In conjunction with finite element and fracture mechanics analysis, the thermal shock fracture initiation and crack propagation behaviour of carbon anodes were characterised in the thermal shock tests. The thermal shock test results were correlated with the thermal shock resistance parameters derived from thermal and mechanical properties. It was found that increased extent of non-linear stress–strain behaviour, which can be described by a lower brittleness function, χ, and a higher γWOF/γi ratio, leads to significantly higher thermal shock crack propagation resistance.

Applications of fiber optic pulsed photothermal radiometry

Pulsed photothermal radiometry is a nondestructive technique for measurements of surface and subsurface thermal parameters of a wide variety of materials. A fiber optic pulsed photothermal radiometric system is constructed and its feasibility is demonstrated. The radiometric system includes a pulsed CO2 laser, an IR detector, and two IR transmitting silver halide optical fibers for delivering IR radiation to and from the sample. A weak laser pulse, absorbed by the sample, initially heats the sample surface. The time evolution of the transient emitted IR radiation is measured and analyzed. The results establish the feasibility of using the fiber optic pulsed photothermal radiometric system to measure coating thickness, to detect flaws, and to diagnose thermal damage in tissue. This fiber optic method would be useful for industrial and medical applications.

Blanket diagnostics system for ITER

Measurement and diagnostics system for the fusion experimental reactor ITER blanket is discussed in this paper. Diagnostics are proposed to be carried out in three directions: thermalhydraulic parameter measurement; neutron characteristic measurement; and structural metal condition control. The considered system ensures reactor maintenance safety at all regimes, provides the required blanket structure operation life-time by conducting regular measurements and solves scientific experiment tasks. Much attention has been given to thermalhydraulic parameter measurements since they are considered important for reactor for reactor maintenance safety, for structural metal condition control and for instrumentation, for scientific experiments. Thermalhydraulic parameter measurements are also regarded as an ancillary tool for other diagnostics method implementation and mutual checking-up with other diagnostics. How magnetic fields affect the results of thermal parameter measurements when thermocouples are used is discussed.

Comparison between computed and field measured thermal parameters in an atrium building

This paper presents a comparison study between simulation and filed measurements of thermal parameters of an atrium building in Ottawa, Canada. The selected atrium was an enclosed three-storey building with a pyramidal skylight. The atrium was fully conditioned and has open corridors at each storey connecting it to adjacent spaces. The atrium space was used for circulation and reception while adjacent spaces are offices and meeting rooms. The atrium was monitored in June 1995 and in December 1995 to consider extreme conditions of the outdoor climate. The simulation results were obtained using ESP-r computer program. The comparison included those of predicted and measured solar radiation entering the atrium space at the rooftop, and predicted and measured indoor temperatures of the atrium floors. Results for the solar radiation showed good agreement between the measured and predicted values. When the mechanical system was turned off, the predicted temperatures were within ±2°C of the measured temperatures in winter. In summer, however, the predicted temperatures were 2–3°C higher than the measured temperatures.

Sub-micrometer thermal physics – An overview on SThM techniques

The historical development and present state of the art of scanning thermal microscopy (SThM) – temperature profiling, thermography and other measurements of thermal parameters – in the sub-μm range and the relevant thermal sensors are reviewed. The paper proposes a classification scheme for the various experimental arrangements of STM and AFM based SThM's. Limitations of the SThM technique and future prospects are briefly discussed.

Defects in noble gas crystals

Direct measurements of thermal vacancy formation parameters, carried out for the whole family of noble gas crystals from xenon to the various solid heliums, reveal interesting patterns. A case study of vacancy measurements on solid neon by Schoknecht, not previously published, illustrates the conceptual advantages and experimental challenges of the direct X-ray and length method. Vacancy measurements on all noble gas solids together with related measurements of self-diffusion are systematically reviewed, the results are correlated, and comparisons are made to atomic and to bulk crystal properties. Interstitials and clusters are also mentioned. The relative importance of quantum effects and of multibody interactions is shown for point defects in each of the noble gas crystals.

Measurement of thermal parameters of solids by a modified photodeflection method

Alexej L. Glazov Kyrill L. Muratikov Physical-Technical Institute of RAS Politeknicheskaya 26 194021 St. Petersburg, Russia E-mail: klm@holo.ioffe.rssi.ru Abstract. A modified photodeflection method based on the wave optics approach is proposed for the thermal parameter measurement of volume materials and thin films. Experimental and theoretical results of the application of this method to measurements of the thermal parameters of solids are presented. It is shown that the modified photodeflection method can be used in a wide frequency range of thermal waves and provides a lower mean squared error between experimental and theoretical results in comparison with the ordinary method. © 1997 Society of Photo-Optical Instrumentation Engineers.

Photoacoustic frequency heat-transmission technique: Thermal and carrier transport parameters measurements in silicon

Photoacoustic frequency heat-transmission technique is used to study thermal and carrier transport properties in low-doped silicon wafers. Amplitude and phase photoacoustic signals as a function of modulation frequency of incident optical beam are measured using different experimental conditions. The thermal diffusivity, coefficient of excess carrier diffusion, carrier lifetime, and the surface recombination velocity were determined by comparing experimental results and calculated theoretical photoacoustic signals. The suitability of the photoacoustic frequency heat-transmission technique as a contactless diagnostic method is assessed in comparison with the more conventional photothermal deflection and photothermal modulated reflection techniques.

Response of the outer ionosphere to a magnetic storm at equinox

The observations of the ACTIVE Project satellites in the interval of March 17–23, 1990 were analyzed for the purpose of studying the response of the outer ionosphere to the magnetic storm with SSC on March 20 at 22.43 UT. In particular, measurements of thermal plasma parameters were used, but VLF broadband measurements and data on energetic ion and electron fluxes in the range of 17.7–272 keV were also available. The results of this case study show that the observations in the morning sector at altitudes around 2000 km reflect well the state of the plasmasphere during enhanced activity, namely the depth to which the plasmasphere has been affected by enhanced magnetospheric convection. They also provide the possibility of monitoring the initial phase of recovery. The early evening observations of the plasma parameters in the outer ionosphere at altitudes of 500–1000 km indicate a distinct trough in electron concentration. In the dusk sector, the equatorward edge of this trough can be assumed to be the projection of the equatorial plasmapause. This, combined with the occurrence of electron temperature peaks and with the morning plasmapause position, enables one to judge whether the plasmaspheric bulge has formed and whether an inner plasmapause has occurred.

Combined standard(SPPE) and inverse(IPPE) photopyroelectric configurations for measurement of dynamic thermal parameters of saturated and unsaturated fatty acids

Combined SPPE-IPPE method is proposed to obtain thermal parameters (thermal effusivity, diffusivity, conductivity and volume specific heat) of saturated (caproic C1O:O) and monoenoic unsaturated (oleic C18: 1, cis) fatty acids. The method was also used to investigate temperature behaviour of thermal parameters (around the melting point) for lauric acid (C12:O). The combined SPPE-IPPE approach eliminates problems associated with sample's transparency and thickness control.

Harmonic heat flow in isotropic layered systems and its use for thin film thermal conductivity measurements

A theoretical model is presented describing harmonic heat flow in a two layer system heated by a modulated Gaussian laser beam. Amplitude and phase of the modulated temperature rise in the layers, as well as in the backing substrate and adjacent atmosphere, are calculated by solving the three-dimensional heat conduction equation with a source term including exponential absorption of the laser light in one or two layers. Heat conduction is assumed to be isotropic throughout the system, however, a thermal contact resistance between the two layers can be taken into account. Results are presented for single and double layer systems of gold and various dielectric thin film materials on glass substrates. Amplitude and phase of the harmonic temperature variation are calculated either as a function of position in the sample system or at the surface as a function of the laser beam modulation frequency. It is found that both amplitude and phase of the calculated temperature rise exhibit typical thin film features in their frequency dependence, however, the phase is more sensitive to thin film phenomena than the amplitude. The phase shows typical extrema in that frequency region, where the thermal diffusion length in the film is equal to the film thickness. Based on these findings, we demonstrate how these calculations can be utilized for the interpretation of thin film thermal parameter measurements. The influence of thermal wave interference is demonstrated, and it is discussed how the main thermal parameters like conductivity, effusivity, and thermal contact resistance of the thin film system can be extracted from measurements by a fit of theoretical curves to experimental data. Applying a simple one-dimensional thermal expansion model, surface displacements for thin film systems are calculated and the applicability of photothermal surface displacement for thin film conductivity measurements is discussed.

Temperature dependence measurements of thermal parameters of solid samples by the relaxation method

A generalization of the relaxation method [Budke and Dieška, Acta Phys. Slov. 35, 27–39 (1985)] has been elaborated. While an application of the relaxation method requires the sample holder temperature to be constant in time, this generalized version admits a polynomial change of the sample holder temperature. Such a temperature course is a very common and realistic one at temperature dependence measurements of thermal parameters.