Simultaneous Measurements Of Thermal Conductivity Research Articles

Chip calorimeter for thermal characterization of bio-chemical solutions

A chip calorimeter to measure thermal properties of bio-chemical fluid samples is successfully demonstrated. The chip calorimeter design enables the simultaneous measurement of thermal conductivity and thermal diffusivity of 2.5 μl liquid samples with high-sensitivity and high-throughput. The micro-calorimeter consists of two silicon nitride membranes, with integrated heaters and thermopiles that are 300 μm apart and enclose the liquid chamber. The sensor shows 5 V/W sensitivity and 200 K/W thermal resistance for water. The applicability of the micro-calorimeter to bio-chemical fluids thermal characterization is demonstrated by measuring thermal conductivity and thermal diffusivity of methanol–water mixtures and protein aqueous solutions (bovine serum albumin, BSA). Methanol–water mixtures thermal properties reveal good agreement with earlier reported experimental and theoretical data, showing approximately 2% deviation. Thermal properties of BSA solutions with concentrations up to 20% (w/v) were measured and values for thermal conductivity and diffusivity of (pure) BSA were estimated to be 0.20 W/Km and 0.64 × 10 −7 m 2/s, respectively. The fluidic chip-calorimeter resolves thermal properties for concentrations down to 1% of both methanol and BSA.

Alternative fitting procedures to enhance the performance of resistive sensors for thermal transient measurements

The main concern in most of transient techniques is to obtain a controlled heat flow in a prescribed direction, so that the actual boundary conditions in the experiment agree with those assumed in the theory. Enhancements of the fitting procedures in transient dynamic techniques have been established. One of these dynamic techniques known as the extended dynamic plane source is discussed in details. This technique has been used for simultaneous measurements of thermal conductivity, diffusivity and the specific heat from a single transient recording of the temperature increase. The technique uses a resistive sensor as both, a plane heat source and temperature sensor, i.e. in similar manner as the wire in the transient hot-wire method. The sensor consists of a resistive heater pattern cut from a thin sheet of metal (Ni) covered on both sides with thin layers of an insulating material. The conducting pattern of the sensor, known as the hot-disk configuration, has the shape of spiral strips. Infrared camera images of the sensor were taken, at the beginning of the transient recording, to illustrate the deviations from the ideal conditions due to design defects within the sensor. Alternative fitting procedures have been introduced in order to meet the design criteria of heat and temperature sensor and to fulfil the isothermal boundary conditions required by experimental setup. Within the total time of transient recording, and using a sequence of computational steps, it is possible to find a correct “optimal” time interval to enhance the fitting procedures. These computational steps are based on fitting procedures that provides the selection of the optimal time interval within the total measuring time and thus to obtain more accurate and reliable results. These procedures have been tested using measurements on acrylic “Plexiglas” sample; the corresponding deviations from published data did not exceed 1.5% and 2% in thermal conductivity and diffusivity, respectively. It is another alternative to the standard fitting procedures which mainly based on linear regression and least square fitting. It is anticipated that these fitting procedures have the potential to be used in similar transient techniques.

フォトサーマル赤外検知法を用いた超伝導薄膜（YBCO）の熱伝導率と温度伝導率の同時測定

フォトサーマル赤外検知法を用いた超伝導薄膜（YBCO）の熱伝導率と温度伝導率の同時測定

Electrothermal performance and growth of single phase in barium doped Bi-2223 high-Tc superconductors

Solid state reaction method was used to synthesize the high-Tc superconducting material with nominal composition Bi1.6Pb0.4Sr1.6Ba0.4Ca2Cu3Oy. This paper investigates the associations among macroscopic physical properties and features at atomic level for the prepared samples. The samples were preliminary analyzed by dc electrical resistivity and ac magnetic susceptibility. After that thermal transport, electrothermal conductivity and thermoelectric properties all as a function of temperature (from room down to liquid nitrogen temperature) were measured. X-ray diffraction studies were also done for structural analysis. All the above measurements showed that in the samples, there exists almost a single high- Tc phase with Tc,0 ∼ 110±1K. The lattice constants of the material were determined by indexing the diffraction peaks. Samples were investigated for thermal transport properties, i.e. thermal conductivity, thermal diffusivity and heat capacity per unit volume. Thermal transport properties were measured by a newly developed and calibrated Advantageous Transient Plane Source method. Simultaneous measurement of thermal conductivity and thermal diffusivity made it possible to estimate specific heat and the Debye temperature TD. Thermoelectric power (Seebeck Coefficient) and electrothermal conductivity were also measured with a recently developed and attuned apparatus. Using dc electrical resistivity, thermal conductivity and thermoelectric power, the Figure of merit factor was also calculated.

Determination of Thermal Parameters of Nanostructures Exhibiting One-Dimensional Heat Flow Through a Thermal Transient Method

AbstractWe present an improved methodology for a thermal transient method enabling simultaneous measurement of thermal conductivity and specific heat of nanoscale structures with one-dimensional heat flow. The temporal response of a sample to finite duration heat pulse inputs for both short (1 ns) and long (5μs) pulses is analyzed and exploited to deduce the thermal properties. Excellent agreement has been obtained between the recovered physical parameters and computational simulations.

Thermal and electrothermal characterization of bismuth based high-Tc superconductors

Abstract This paper investigates the relationships among macroscopic physical properties and features at atomic level for the high- T c superconducting material with nominal composition Bi 1.6 Pb 0.4 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O y , which was prepared by a solid-state reaction method. The samples were analyzed by dc electrical resistivity, ac susceptibility, thermal transport, electrothermal conductivity and thermoelectric properties all as a function of temperature (from room down to LN 2 temperature). Room temperature X-ray diffraction studies were also done. All the above measurements showed that in the samples, there exists almost a single high- T c phase with T c,0 ≃ 110 ± 1 K. The lattice constants of the material were determined by indexing the diffraction peaks. Samples are investigated for thermal transport properties, i.e. thermal conductivity, thermal diffusivity and heat capacity per unit volume, by an advantageous transient plane source method. Simultaneous measurement of thermal conductivity and thermal diffusivity makes it possible to estimate specific heat and the Debye temperature Θ D . Thermoelectric power (Seebeck coefficient) and electrothermal conductivity is also measured with a newly developed and calibrated apparatus. Using electrical resistivity, thermal conductivity and thermoelectric power, the Figure of merit factor was calculated.

Simultaneous measurement of thermal conductivity, thermal diffusivity and prediction of effective thermal conductivity of porous consolidated igneous rocks at room temperature

Thermal conductivity, thermal diffusivity and heat capacity per unit volume of porous consolidated igneous rocks have been measured, simultaneously by Gustafsson's probe at room temperature and normal pressure using air as saturant. Data are presented for eleven samples of dunite, ranging in porosity from 0.130 to 0.665% by volume, taken from Chillas near Gilgit, Pakistan. The porosity and density parameters have been measured using American Society of Testing and Materials (ASTM) standards at ambient conditions. The mineral composition of samples has been analysed from their thin sections (petrography). An empirical model to predict the thermal conductivity of porous consolidated igneous rocks is also proposed. The thermal conductivities are predicted by some of the existing models along with the proposed one. It is observed that the values of effective thermal conductivity predicted by the proposed model are in agreement with the experimental thermal conductivity data within 6%.

Thermal properties of wood-gypsum boards

Transient simultaneous measurements of thermal conductivity, volume heat capacity and thermal diffusivity of laboratory wood-gypsum boards have been performed with ISOMET 2104 at room temperature. The influences of wood particle content, density and moisture content on thermal properties were investigated. The measurements were performed in a direction perpendicular to the board plane. The effect of density and wood particle content on the thermal properties may be related to the presence of voids both between and inside particles. It seems, that the dominant mechanism of heat transfer across the board is the heat conduction through the voids. Wood-gypsum boards with a density of 850–1300 kg/m3, a moisture content of 2–11% and a wood particle content of 0–35% have the following thermal conductivity of 0.189–0.753 W m-1 K-1, volume heat capacity of 0.683–1.43×106 J m-3 K-1 and thermal diffusivity of 0.171–0.367×10-6 m2 s-1; their magnitudes are higher than those ones of OSB, MDF, particleboard and plywood.

Study of the thermal behaviour of Bi(Pb)Sr(Ba)-2223 high- Tc granular superconductors

Thermal measurements were performed to correlate the microstructural and morphological modifications induced by barium doping and the superconducting properties of Bi(Pb)Sr(Ba)-2223 superconductors. The samples were prepared by a solid state reaction method. The samples were then analyzed by dc electrical resistivity, thermal transport and thermoelectric properties all as a function of temperature (from room down to 77 K). X-ray diffraction studies were also done and the lattice constants of the material were determined by indexing the diffraction peaks. All the above measurements showed that in the samples, there exists almost a single high- T c phase with T c,0 ≃ 110 ± 1 K. Samples are investigated for thermal transport properties, i.e. thermal conductivity, thermal diffusivity and heat capacity per unit volume, by an advantageous transient plane source method. Simultaneous measurement of thermal conductivity and thermal diffusivity makes it feasible to estimate specific heat and the Debye temperature Θ D, as well as to separate the electron and phonon contributions to thermal conductivity and diffusivity. Thermoelectric power (Seebeck Coefficient) is measured with newly developed and calibrated apparatus. This newly developed apparatus is easy to use, simple in operation and is interfaced to computer for measurements and calculations. Using electrical resistivity, thermal conductivity and thermoelectric power, the figure of merit factor is calculated.

Simultaneous measurements of thermal conductivity and thermal diffusivity for garnet and olivine under high pressure

Simultaneous measurements of thermal conductivity and thermal diffusivity for garnet and olivine under high pressure

Simultaneous measurements of thermal conductivity and thermal diffusivity for garnet and olivine under high pressure

Thermal conductivity λ and thermal diffusivity κ have been measured simultaneously for garnet (Al 73Py 25Gr 1Sp 1) and olivine (Fo 93Fa 7) single crystals up to 8.3 GPa and 1100 K by using a pulse heating method. Anisotropy of thermal conduction is investigated along the three crystallographic axes, [1 0 0], [0 1 0], and [0 0 1] in olivine. The pressure dependence of κ, or dln κ/d P, is determined to be 0.03–0.04 GPa −1 for the three crystallographic direction in olivine and 0.03 GPa −1 for garnet, while dln λ/d P is determined to be ∼0.04 GPa −1 for olivine and 0.03 GPa −1 for garnet. The anisotropy in thermal diffusivity or thermal conductivity of olivine is clearly observed in the present experimental range of pressure and temperature. It is likely that the anisotropy in thermal conduction would be maintained throughout the olivine stability field in the mantle down to 410 km depth. Heat capacities of olivine and garnet are calculated from the present κ and λ. Both the present heat capacities of olivine and garnet are consistent with the previously reported values within 5%. Those obtained for the three crystallographic direction in olivine are also consistent with each other within 6%. Further, the effect of basalt–eclogite transition on heat transportation is discussed based on the present results for garnet. It implies that the eclogite layer of the slab transmits thermal energy more effectively than the upper basaltic layer.

Simultaneous measurements of thermal conductivity and diffusivity of Se80Te20-xInx (x = 2, 4, 6 and 10) chalcogenide glasses at room temperature

Measurements of thermal conductivity and thermal diffusivity of twin pellets of Se80Te20-xInx (x = 2, 4, 6 and 10) glasses, prepared under a load of 5 tons were carried out at room temperature using transient plane source (TPS) technique. The measured values of both thermal conductivity and diffusivity were used to determine the specific heat per unit volume of the said materials in the composition range of investigation. Results indicated that both the values of thermal conductivity and thermal diffusivity increased with the addition of indium at the cost of tellurium whereas the specific heat remained almost constant. This compositional dependence behaviour of the thermal conductivity and diffusivity has been explained in terms of the iono-covalent type of bond which In makes with Se as it is incorporated in the Se-Te glass.

Further examination of the transient hot-wire method for the simultaneous measurement of thermal conductivity and thermal diffusivity

The transient hot-wire technique is re-investigated in order to measure, simultaneously and accurately, the thermal conductivity λ and thermal diffusivity κ of a liquid. Newly derived effective temperatures Tλ and Tκ that are associated with the measured values of the thermal conductivity and thermal diffusivity are introduced and replace the previously used temperatures T0 and Tm. Higher-order corrections due to the thermal properties of the wire material are also re-investigated; these may be significant for experiments on lower-density substances or when using a hot-wire sensor with a thicker wire. The radiation (photons) emitted from or absorbed into the medium is discussed, and its contribution is taken to be part of the ordinary heat-conduction phenomenon exhibited by carriers such as phonons, electrons and molecules. The new system was tested by measuring the thermal conductivity and thermal diffusivity of n-heptane, n-pentane and iso-pentane, and values for their volumic heat capacities were calculated from the ratios λ/κ. The relative combined expanded uncertainties of the measured values (coverage factor k = 2) were 0.38 % for λ, and 1.7 % for κ and cpρ.

Simultaneous Measurements of Thermal Conductivity and Diffusivity of Se85-xTe15Sbx (x = 2, 4, 6, 8, and 10) Chalcogenide Glasses at Room Temperature

Measurements of thermal conductivity and thermal diffusivity of twin pellets of Se80Te20-xInx (x = 2, 4, 6 and 10) glasses, prepared under a load of 5 tons were carried out at room temperature using transient plane source (TPS) technique. The measured values of both thermal conductivity and diffusivity were used to determine the specific heat per unit volume of the said materials in the composition range of investigation. Results indicated that both the values of thermal conductivity and thermal diffusivity increased with the addition of indium at the cost of tellurium whereas the specific heat remained almost constant. This compositional dependence behaviour of the thermal conductivity and diffusivity has been explained in terms of the iono-covalent type of bond which In makes with Se as it is incorporated in the Se-Te glass.

Heat transfer and ion migration in the system Li 2SO 4–Na 2SO 4

The transient plane source technique has been used for simultaneous measurements of thermal conductivity and diffusivity in the lithium–sodium sulphate system starting near 300 K. Samples with 100, 77.5, or 50% Li 2SO 4 behave differently from pure Na 2SO 4. In the first case both the thermal conductivity and the diffusivity start to increase rapidly at about 640 K, while the crystal structure remains monoclinic for Li 2SO 4 and trigonal for LiNaSO 4. Concerning pure Li 2SO 4, there is an additional discontinuous increase of the two thermal parameters at the structural transition from monoclinic to cubic (fcc) at 850 K, while the temperature gradients become significantly smaller in the cubic phase than in the monoclinic one. In contrast, both the thermal conductivity and the diffusivity of Na 2SO 4 decrease over the whole studied temperature range, which includes the phase transitions at 474 K and 520 K. Furthermore, a corresponding study was performed for silver iodide over the range 295–640 K, i.e. on both sides of the phase transition at 420 K. There is an indication of a small decrease of the thermal conductivity and the diffusivity at the phase transition. The high temperature phases fcc Li 2SO 4, bcc LiNaSO 4 and bcc AgI are solid electrolytes, but it is characteristic for the two sulphate phases that a coupled rotation-like motion of the sulphate ions enhances the cation migration. Obviously, such motion is also of importance for heat transport.

Effective thermal conductivity of three-phase styrene butadiene composites

Transient plane source technique was used for the simultaneous measurement of thermal conductivity and thermal diffisivity of three-phase styrene butadiene rubber composites. Two series of styrene butadiene rubber composites were studied, having natural rubber as a variable filler in both the composites along with 10 phr of silica and clay, respectively. The measurements were done at room temperature and normal pressure. The experimental results show that there is a small variation in the thermal conductivity of both the composites with the filler (NR) fraction. It is interesting to note that the thermal conductivity shows a sharp decrease at 10 phr filler loading and then increases. The comparative study of these composites shows that the conductivity as well as the diffusivity of the silica reinforced composites is larger than that of the clay composites. The thermal conductivity of the filler NR has been evaluated using the Agari model. It has also been found that the composite with 40 phr of NR has the maximum thermal conductivity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1799–1803, 2000

Thermal conductivity and diffusivity of wood

Transient simultaneous measurements of thermal conductivity and diffusivity of Swedish wood have been performed with the plane source technique on oven-dry hardwood (birch) samples at room temperature and at 100 °C. The influences of temperature, density, porosity and anisotropy on thermal conduction were investigated. The measurements were done in longitudinal (parallel to the grain) and transverse (intermediate between radial and tangential) directions. As the temperature increased from 20 to 100 °C, the thermal conductivity of each sample increased slightly for both longitudinal and transverse directions. The effect of density and porosity on the thermal conductivity may be related to the presence of other scattering mechanisms such as voids and cell boundaries. It seems that the dominant mechanism of heat transfer across the cell lumina in these types of wood is the heat conduction through the voids. An attempt was made to explain the behaviour of the effective thermal conductivity by adopting a model based on the ratio between heat conduction in parallel and serial layers of gas, liquid, and solid phases.

Ultrasensitive excitation/relaxation calorimeter for simultaneous measurement of thermal conductivity and heat capacity in fluids

An ultrasensitive heat conduction microcalorimeter for fluids with a novel method of data analysis is described. The instrument measures the thermal conductivity (λ) and heat capacity (Cp) simultaneously on the same sample with a resolution of 1 part in 105 for each of these properties. Baseline and sample filling errors are below the instrument resolution. The accuracies for λ and Cp are approximately 1 part in 104, limited primarily by the uncertainty in the properties of the standards used for calibration. The instrument operates essentially isothermally, and is capable of automated temperature stepping between 5 and 55 °C.

Simultaneous measurements of thermal conductivity and thermal diffusivity of liquids under microgravity conditions

A transient short-hot-wire technique is proposed and used to measure the thermal conductivity and thermal diffusivity of liquids simultaneously. The method is based on the numerical evaluation of unsteady heat conduction from a wire with the same length diameter ratio and boundary conditions as those in the experiments. To confirm the applicability and accuracy of this method. Measurements were made for five sample liquids with known thermophysical properties and were performed under both normal gravity and microgravity conditions. The results reveal that the present method determines both the thermal conductivity and the diffusivity within 2 and 5%. respectively. The microgravity experiments clearly indicate that even under normal gravity conditions, natural-convection effects are negligible for at least l s after the start of heating. This method would be particularly suitable for a valuable and expensive liquid, and has a potential for application to electrically conducting and or corrosive liquids when the probe is effectively coated with an insulating and anticorrosive material.

A practical cryogenic resistive sensor for thermal conductivity measurements

The line heat-source is one among many classes of transient methods for measuring thermal properties, such as thermal conductivity, diffusivity and specific heat, which are directly related to heat conduction. Belonging to this category is the transient plane source (TPS) technique for simultaneous measurements of thermal conductivity and diffusivity of solids. The technique uses a ‘resistive element’ made of nickel foil in the form of a bifilar spiral (TPS element/sensor) covered on both sides with an insulating layer of Kapton. For the first time, the calibration procedures of such a sensor have been extended down to 35 K. By fitting the calibration data to a fourth-order polynomial, a reliable equation for the measured resistance of the TPS element covering the whole temperature range of interest (35–300 K) was obtained. A moderate decrease in the sensitivity of this sensor was observed around 60 K; it is attributed to a nearly temperature-independent resistivity coefficient (TCR) behaviour in this temperature range. The sensitivity decline is linked to a design factor that is related to the resistance behaviour of the material used in the construction of the sensor. To improve the practicality of using the sensor in this temperature range,a comparison was made between the behaviour of the TCR values of nickel and silver. It is found that a sensor made of silver foil will improve the accuracy and extend the measurements to lower temperatures.