Measurement Of Thermal Properties Research Articles

Thermal Properties of Backfill Material for Underground Heat Exchange Applications

We are investigating the effect of the thermal properties of backfill material on the efficiency of underground thermal energy systems. We have used aluminum to increase the thermal properties of clay-bentonite and to investigate its potential as a backfill material in underground heat exchange applications. The measurements of thermal properties were made at room temperature using the Transient Plane Source (TPS) technique. The measurements were based on an infinite homogeneous medium using different composites of aluminum and clays in amounts of aluminum concentration ranging from 6 to 25 percent of the sample’s weight. The results confirmed an overall relative increase of 170% and 135% in the thermal conductivity and diffusivity, respectively as the Al content increased by 25%. The estimated average of the thermal transmittance (U-value ) of these samples was in the range from 0.40 to 1.1 W/m2K, which was directly proportional to the relative increase in the measured properties. Our findings can be applied to underground thermal energy systems, ground source heat pumps, and solid dielectric underground transmission lines.

Bone density estimation using tissue heat capacity.

Osteoporosis onset is relatively asymptomatic, the condition often being identified only once a significant fracture occurs, leading to a potentially serious prognosis. Currently, early identification of osteoporosis is complicated by the difficulty in measuring bone density without using x-ray absorptiometry or quantitative ultrasound, so a simpler method for estimating bone density is needed. Given that bone is reported to have a lower specific heat than other tissues, we investigated the possibility of estimating bone density using this difference in tissue thermal properties. The tibia medial surface (shin) and medial malleolus (ankle) of 68 healthy volunteers were cooled using an ice bag, and skin surface temperatures and heat flow were recorded. These measurements were then used to calculate the heat energy transferred per unit temperature. Bone density was estimated by quantitative ultrasound using the T score OSISD, which is the participant's osteo sono-assessment index (OSI) compared to the average OSI of young adults. The heat energy transfer per unit temperature at the shin, but not the ankle, showed a significant negative correlation with T score OSISD (r = -0.413, p = 0.001). Multiple regression analysis showed that heat energy transfer per unit temperature at the shin was a significant predictor of T score OSISD, along with age and height. These results show that tissue thermal property measurements are useful for estimating bone density.

An Inductive Method for Comprehensive Estimation of Temperature-Dependent Electrical and Thermal Properties of Conductive Ferromagnetic Materials

Reliable information about the properties of the processed materials has a significant impact on the effects of their processing. In induction heating processes, this also applies to information about the influence of temperature T on these properties. These are both thermal and electro-magnetic properties. Based on previous studies, a comprehensive experimental method is presented for estimating the temperature characteristics of thermal diffusivity, volumetric heat capacity and resistivity on one measurement station, with particular attention to ferromagnetic materials. The estimation process is carried out on an induction heating stand using forcing signals from an inverter generator. In a computer-controlled cycle that changes the base temperature level, basic measurements of thermal and electrical properties are carried out on a material sample in the form of a cylindrical disk. They are the results of the analysis of the temperature and electromagnetic responses of a material sample to short- and long-term step pulses of a sinusoidal excitation signal with a frequency of approximately 40 kHz. The presented estimation method can be treated as a final method or a preliminary procedure for radically narrowing the variability in decision variables inthe optimization process of simultaneous determination of the sought material characteristics.

Optimized measurement of frozen soil thermal properties using a heat-pulse sensor

The measurement of thermal properties in partially frozen soil is crucial for global climate models. As the primary method for soil thermal property measurement, the Dual-Probe Heat-Pulse (DPHP) sensor experiences significant errors when used in partially frozen soils. The application of heat pulses leads to ice melting, and the existing DPHP theory, which does not consider phase changes, fails to accurately determine thermal conductivity (k) and heat capacity (C) in the temperature range of − 5 °C to 0 °C. There is a lack of DPHP theory specifically designed for use in partially frozen soils. The existing DPHP theory employs the Infinite Linear Source (ILS) approximation, which does not account for the melting process and the moving ice-liquid interface in transient heat conduction theory. Currently, there is no effective and reliable method to assess DPHP errors associated with measuring the thermal properties of partially frozen soil. To accurately determine k and C in frozen soil, it is essential to perform an error analysis regarding ice melting caused by a DPHP heat pulse input. In this study, (1) we considered the latent heat of ice melting and a moving ice-liquid interface in finite element simulations and compared the results with an analytical solution presented by Paterson (1952); (2) we performed simulations of DPHP measurements based on the temperature-dependent ice content, liquid water content, and melting latent heat of three frozen soils used by Watanabe and Wake (2009); (3) based on COMSOL simulation results for the three frozen soils, we determined the optimal heating parameter combinations (heating duration, t0, and accumulated heating energy, ΔQ) to minimize DPHP measurement errors in frozen soil. The results showed that (1) Simulations that included the melting phase changes were in agreement with the analytical solution by Paterson (1952). (2) Including the ice-liquid moving interface significantly altered the spatial distribution characteristics of temperature, which were not captured by the ILS model in terms of the temperature distribution near the interface. (3) Below a temperature of − 5.5 °C, the simulations that included phase changes were consistent with measured results; (4) For partially frozen soils with initial temperatures ranging from − 0.5 °C to 0 °C, the relative errors in thermal conductivity fitted by the ILS model exceeded 100 %. To mitigate the influence of ice melting, we recommend using 200 < ΔQ < 400 J m−1 for sand, loam, and silt loam soils with 8 s < t0 < 60 s. For a loam soil with t0 = 60 s, ΔQ = 800 J m−1 should be used. For a silt loam soil with t0 = 60 s, we recommend using ΔQ = 600 J m−1. If the ILS model is chosen to calculate soil thermal properties, we recommend using 200 <ΔQ < 600 J m−1 and 30 s < t0 < 60 s for sandy and silt loam soils. For a loam soil, we recommend using 400 < ΔQ < 800 J m−1 and 30 s < t0 < 60 s.

Data-Driven Contact-Based Thermosensation for Enhanced Tactile Recognition.

Thermal feedback plays an important role in tactile perception, greatly influencing fields such as autonomous robot systems and virtual reality. The further development of intelligent systems demands enhanced thermosensation, such as the measurement of thermal properties of objects to aid in more accurate system perception. However, this continues to present certain challenges in contact-based scenarios. For this reason, this study innovates by using the concept of semi-infinite equivalence to design a thermosensation system. A discrete transient heat transfer model was established. Subsequently, a data-driven method was introduced, integrating the developed model with a back propagation (BP) neural network containing dual hidden layers, to facilitate accurate calculation for contact materials. The network was trained using the thermophysical data of 67 types of materials generated by the heat transfer model. An experimental setup, employing flexible thin-film devices, was constructed to measure three solid materials under various heating conditions. Results indicated that measurement errors stayed within 10% for thermal conductivity and 20% for thermal diffusion. This approach not only enables quick, quantitative calculation and identification of contact materials but also simplifies the measurement process by eliminating the need for initial temperature adjustments, and minimizing errors due to model complexity.

A novel heat transfer characterization method for a thermal management scheme of 3D-IC chips

A novel surface-modified silicon-based thermal management technology has been proposed for 3D IC architecture in this study. 2 × 2 cm2 double sides polished silicon chips’ surface with micro-fin (MF) and micro-pin fin (MPF) structures have been achieved by applying silicon microfabrication technology of deep reactive ion etching, which is applicable to the interlayer of 3D IC packaging technology. By integrating a mini wind tunnel with Raman spectrometer, the transient thermal property measurement system is originally designed to evaluate the cooling capability of the surface-modified silicon interlayer. Finite Element Analysis was involved to confirm this view by taking fluid dynamics and heat transfer into account. The sample with 100 × 100 µm2 MPF structure expresses the appropriate exponential decay time constant τ (with unit of 1), which is 4.71 and 8.53 under cooling and heating measurement conditions, respectively. This also proved that the combination of Raman thermometry with forced gas flow could be a relevant measurement tool for transient thermal property.

Accelerated thermal property mapping of TRISO advanced nuclear fuel

TRistructural ISOtropic (TRISO) fuel is a leading-edge nuclear fuel form representing a departure from the more traditional nuclear fuel forms utilized in the reactor fleet of today. Rather than a monolithic fuel pellet of uranium dioxide, integral fuel forms containing TRISO fuel are composed of thousands of microencapsulated uranium-bearing fuel kernels and individually coated with multiple layers of pyrolytic carbon and silicon carbide. These multilayered ceramic coatings serve as an environmental barrier to ensure radioactive and chemically reactive fission products are contained within the reactor fuel elements, but also participate in the transfer of heat generated in the nuclear fuel to the coolant – the primary purpose of a nuclear reactor. Since traditional thermal property measurement techniques, such as laser flash analysis, would be unable to resolve the thermal properties of the individual TRISO coating layers, a simplified frequency-domain thermoreflectance technique has been developed to rapidly map the thermal properties of TRISO particles. Using this technique, the thermal properties of TRISO particles have been mapped from room temperature up to 1000 °C to examine the spatial variation and temperature-dependency of the thermal properties within each layer. Additionally, spatial-domain thermoreflectance was used to examine the anisotropy of the thermal properties for each layer at different locations within a single TRISO particle, and across multiple TRISO particles to assess the intra- and inter-particle uniformity of thermal properties, respectively. To elucidate the underlying causes for the measured variations in thermal properties, scanning electron microscopy and Raman spectroscopy were used to examine variations in microstructure and chemical bonding within the different coating layers. Results from this work are then compared with previous examinations of TRISO fuel particles and microstructurally driven mechanisms for the variations in the measured thermal properties of the different carbonaceous layers are discussed.

High-temperature and high-pressure thermal property measurements of SiO2 crystals.

The investigation of materials' behavior under high-temperature and high-pressure conditions, such as the correlation with structural characteristics and thermal properties, holds significant importance. However, the challenges associated with the experimental implementation have, to a certain extent, constrained such research endeavors. We utilized the ultrafast laser based non-contact thermal measurement method combined with an externally heated moissanite-anvil-cell to characterize the thermal conductivity of [10-10] oriented SiO2 crystals under high temperature (300-830K) and high pressure (0-15GPa) conditions. We investigated the impact of extreme conditions on the microstructure from both Raman spectroscopy and thermal perspectives. The presence of kinetic hindrances associated with the transformation of α-quartz to coesite and stishovite was identified and confirmed. It expands the comprehension and application of the SiO2 pressure-temperature phase diagram in this range and provides insights into the intricate relationship between extreme environments and material structure formation through the analysis of thermal characteristics.

The uniform and robust 8-inch CVD diamond plate generated by dual-magnetic field controlled DC Jet CVD

Diamond is a highly attractive material for many applications in material science, engineering, chemistry, and biology because of its favorable properties. The preparation of large-area freestanding diamond plate can greatly reduce the production cost of diamond and promote the industrialization of diamond. In this study, the dual-magnetic field mode was introduced to optimize the magnetic field distribution in direct current arc plasma jet chemical vapor deposition (DC Jet CVD) system, and the arc plasma was effectively controlled under the coupling of electric field and magnetic field. The uniformity of the plasma distribution above the substrate surface is significantly improved, resulting in long-term stable and uniform growth of the 8-inch freestanding diamond plate. The influence of dual-magnetic field mode on magnetic field generation, arc feature, and reactive group distribution was studied. 8-inch freestanding diamond plates with an average thickness of 2.8 mm were prepared by dual-magnetic controlled DC Jet CVD. The results showed that the 8-inch diamond plate preferred a high (220) orientation, and the deviation of thickness of which was around 10 % of the averaged values. Raman spectroscopy of diamond revealed a 6.6 cm−1 of full width at half maximum (FWHM) and calculated 1.20 GPa compressive stress in the 8-inch diamond plate. By means of mechanical and thermal property measurements, the large area diamond plate shows a robust structure with the average values of three-point bending fracture strength of 987.2 MPa, and extremely high thermal conductivity of 1797.8 W/(m·k) as well. The deviation of three-point bending fracture strength and the thermal conductivity over the 8-inch diamond plate was around 7.9 % and 12.6 % of the respective averaged values.

An Open‐Source Multifunctional Testing Platform for Optical Phase Change Materials

Owing to their unique tunable optical properties, chalcogenide phase change materials are increasingly being investigated for optics and photonics applications. However, in situ characterization of their phase transition characteristics is a capability that remains inaccessible to many researchers. Herein, a multifunctional silicon microheater platform capable of in situ measurement of structural, kinetic, optical, and thermal properties of these materials is introduced. The platform can be fabricated leveraging industry‐standard silicon foundry manufacturing processes. This platform is fully open‐sourced, including complete hardware design and associated software codes.

Glycerol-treated polypropylene/carbon black nanocomposites: Analysis of electrical, rheological, thermal and mechanical properties

Electrically conductive nanocomposites based on polypropylene (PP) were prepared using carbon black (CB) nanoparticles via melt blending in the presence of glycerol and castor oil as hydroxyl functional dispersing aids and maleic anhydride–grafted polypropylene (MAgPP) as a compatibilizer. Initially, electrical conductivity of PP/CB nanocomposites with different dosages of both CB nanoparticles and dispersing aids were investigated through electrical analysis. Results indicated that castor oil had no beneficial effects on electrical conductivity. However, the efficiency of 3 wt% loading of glycerol was verified through measurements of electrical, rheological, thermal and mechanical properties as well as by morphological studies. The volume electrical conductivity value of PP nanocomposites containing 12 wt% CB significantly enhanced to 1.2 × 10−4 S/cm by adding 3 wt% glycerol in compared with nanocomposite without glycerol with the volume conductivity value of 1.8 × 10−6 S/cm. Incorporation of optimum amount of glycerol favoured the dispersion of nanofiller in the matrix which was confirmed by scanning electron microscopy observations, leading to higher conductivity due to better formation of conductive pathways within the matrix. Additionally, at the same concentration of CB nanofiller, samples treated with 3 wt% glycerol showed higher melting temperatures, storage modulus ( Gˊ), complex viscosity, tensile modulus and elongation at break. These findings indicate that adding an optimum amount of an efficient hydroxyl functional component like glycerol into PP/CB nanocomposite can be a promising way to enhance the electrically conductive performance while other properties could be maintained well or even improved.

Preparation and properties of a porous ZrO2/SiZrBOC ceramic matrix composite with high temperature resistance and low thermal conductivity

In this study, porous ZrO2/SiZrBOC and SiZrBOC ceramic matrix composites were produced via vacuum impregnation method, using SiZrBOC ceramic precursor as a matrix, ZrO2 fiber prepared via electrospinning as the reinforcing agent and polyurethane foam as a skeleton. Polyurethane foam with open porosity is rather a substrate for the creation of a skeletal 3D structure. The preparation process and pyrolysis mechanism of ZrO2/SiZrBOC polyurethane foam impregnated with a precursor solution were expounded. The thermal conductivity tests and mechanical property measurements show that the lowest thermal conductivity (0.0378 W m−1 K−1) was achieved in the ZrO2/SiZrBOC ceramic matrix composite at the pyrolysis temperature of 800 ℃, being much inferior to that of the SiZrBOC composite (0.0861 W m−1 K−1). At 1400 ℃, the maximum compressive strength of the porous ZrO2/SiZrBOC ceramic matrix composites reached a value of 1.37 MPa, while that of the SiZrBOC composites was 0.22 MPa only. Therefore, the addition of ZrO2 fibers improved the compressive strength and thermal insulation properties of the composites.

Measurement of coal quality by a home-made photoacoustic spectrometer

In present time, photoacoustic spectroscopy (PAS) has become a popular technique for measurements of thermal properties of biological, chemical, geological samples. The PAS is suitable for any phase of material such as solid, liquid, gel, suspension and gas etc. In this work authors have fabricated a photoacoustic cell & a pre-amplifier, and optimized both for maximum photoacoustic (PA) signal. Optimum inert cavity volume of the cell was measured to 3.20 × 106 m3. After that, coals samples were collected from five different places of Jharkhand state, India for the study of their quality with PA spectroscopy. The X-ray diffraction (XRD) data has confirmed that four samples have different class of quartz and one sample is very close to kaolinite. The field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray analysis (EDAX) had shown non-uniform bulk like structure containing various elementals. All samples are distinguished by their quality using PAS and verified them with the Raman spectroscopy. Finally, the authors have measured thermal diffusivity of each samples. The maximum value of thermal diffusivity is measured for kaolinite structure having value of 13.4673 × 10–8 m2/s.

Advancement Toward the Experimental Measurement of the Lead–Bismuth Eutectic Thermal Properties Using Differential Scanning Calorimetry Technique

Abstract The differential scanning calorimetry (DSC) method has recently emerged as a sophisticated and precise technique for promising contributions to the thermal analysis of various materials, including heavy liquid metal (HLM) coolants. However, there is a lack of experimental studies on the thermal properties of lead-based fluids, such as lead–bismuth eutectic (LBE) and lead–lithium eutectic, which are potential candidates for use as coolants, breeders, and neutron multipliers in advanced nuclear systems like the fourth-generation lead-cooled fast reactor. The available experimental data on the thermal properties of LBE and other lead-based fluids is limited, and the measurements have significant uncertainty. In addition, the composition of components used in the previous studies is inconsistent, and the environmental conditions were often unknown. Therefore, to fill these gaps and advance the thermal properties measurement technique for heavy liquid metal coolants, ENEA Brasimone, in collaboration with DICI-UNIPI, has installed a DSC instrument setup. The experiments performed at the installed DSC setup are focused on measuring some essential thermal properties of LBE using DSC. The experience gained from this work will facilitate the measurement of other fluids based on lead alloy, especially lead–lithium eutectic, a potential candidate for breeder, coolant, and neutron multiplier in demonstration power plant fusion reactors. This study represents the first effort to advance the DSC approach for accurately measuring the thermal characteristics of heavy liquid metals that are highly reactive, such as lead–lithium, which has significant potential in advanced nuclear systems.

Geothermal gradients in a high-organic content landfill

Geothermal gradients in a high-organic content landfill

Measuring Thermal Diffusivity of Azoheteroarene Thin Layers by Photothermal Beam Deflection and Photothermal Lens Methods.

Measurement of thermal properties of thin films is challenging. In particular, thermal characterization is very difficult in semi-transparent samples. Here, we use two photothermal methods to obtain information about the thermal diffusivity as well as thermal conductivity of azoheteroarene functionalized polymer thin layers. The photothermal beam deflection (PBD) method is employed to gather data directly on thermal conductivity and thermal diffusivity, while the thermal lens (TL) method is employed to measure the effective thermal diffusivity. Consequently, the thermal diffusivity of the layers is indirectly estimated from the effective thermal diffusivity using a well-established theoretical relationship. Despite the utilization of distinct methods, our study reveals a remarkable consistency in the highly accurate results obtained from both approaches. This remarkable agreement reaffirms the reliability and mutual compatibility of the employed methods, highlighting their shared ability to provide accurate and congruent outcomes.

Hygrothermal and strength properties of cement mortars containing cenospheres

This study characterizes the hygrothermal and microstructural properties of cement composites containing aluminosilicate cenospheres. It involved the preparation of six mortar mixtures based on CEM I 42.5R cement, in which cenospheres accounted for 0 to 100 % of the aggregate content. The research included measurements of thermal properties, compressive and bending strength tests, density tests on the cured mortars, determination of pore distribution and total porosity, and qualitative assessment of the cenosphere-cement matrix contact zone. However, the main emphasis was on moisture-related parameters. The publication discusses the effect of using cenospheres as a substitute for natural sand on water absorption, capillary absorption, and the sorption and desorption of water by the tested composites, along with the influence of individual microstructural properties on moisture properties. The results showed that increasing the amount of cenospheres added as a sand substitute contributed to an increase in the water absorption of the composite and in parallel reduction in the capillary rise coefficient. The increase in the content of cenospheres caused also a clear increase in the sorption capacity of mortars. Moreover as the statistically average distances between the pores decreased, the thermal conductivity of the composites also decreased. Both when considering the porosity and the spacing factor, the conductivity decrease with wet composites was faster than with dry ones. With decreasing distances between the pores, the compressive strength also decreased significantly. Higher content of cenospheres also reduced the density of the composite and at the same time, increased the specific surface area, which contributed to the reduction in the capillary absorption coefficient and the increase in the durability of the entire composite. In addition, relatively good insulating properties of these composites (λ as low as 0.25 W/mK) in comparison to ordinary cement-based mortars make them interesting alternative to traditional solutions, while the appropriate mechanical strength (compressive strength in the range of 37.68 to 17.74 MPa) makes them suitable even for use as structural elements.

High throughput, spatially resolved thermal properties measurement using attachable and reusable 3ω sensors.

The 3ω method is a well-established thermal technique used to measure the thermal conductivity of materials and the thermal resistance of interfaces. It has significant advantages over other steady state and transient thermal techniques in its ability to provide spatially resolved thermal property measurements over a wide range of thermal conductivity. Despite its advantages, it has been restricted to lab-scale use because of the difficulty involved in sample preparation and sensor fabrication and is limited to non-metallic substrates. High-throughput 3ω measurements with reusable sensors have not been realized yet. In this work, we demonstrate a method of applying reusable 3ω sensors fabricated on flexible polyimide films to measure bulk and spatially resolved thermal properties. We establish the limits of thermal conductivity measurement with the method to be 1 to 200 W/mK, and within the measurement limit, we verify the method by comparing the measured thermal conductivities of standard samples with established values. From the 3ω measurements, we also determine the thermal resistance of an interlayer of thermal grease as a function of pressure and compare it against the resistance calculated from direct thickness measurements to demonstrate the ability of this method to provide spatially resolved subsurface information. The technique presented is general and applicable to both metallic and non-metallic substrates, providing a method for high-throughput 3ω measurements with reusable sensors and without considerable sample preparation.

Removing of cationic dyes using self-cleaning membranes-based PVC/nano-cellulose combined with titanium aluminate

This research used the phase inversion approach to construct polyvinyl chloride nanocellulose@titanium aluminate nanocomposite membranes (PVC/NC@TALCM) to adsorb and filter dye from wastewater. FTIR, XRD, and SEM were used to determine the adsorptive nanocomposite membrane that had been synthesized. The thermal and electrical properties measurements were carried out using a static system. The influence of several adsorbent dosages, pH, and dye concentrations on the nanocomposite membrane’s adsorption ability was investigated. Using a dead-end filtration system, the PVC-NC@TALCM was evaluated as a pressure filtration membrane system. It was found that 98.6% of MB dye was removed by PVC-NC@TALCM membrane, which was loaded with 5% titanium aluminate at pH 10. The kinetic adsorption studies indicated that the adsorption of MB onto the PVC-NC@TALCM nanocomposite membrane obeys pseudo-second-order that indicates the chemosorption process. The isotherm data were described using Freundlich and Langmuir models, and the Freundlich isotherms were shown to be more closely match the experimental data than the Langmuir model. Finally, the PVC-NC@TALCM nanocomposite membrane was economical, environmentally friendly, and self-cleaning.

Dual cross-linked starch hydrogel for eugenol encapsulation and the formation of hydrogen bonds on textural hydrogel

Physical and chemical cross-linked hydrogels combining N, N′-Methylenebisacrylamide (MBA)-grafted starch (MBAS) and sorbitol were successfully prepared and encapsulated with eugenol in this work. The dense porous structure with diameter of 10–15 μm and strong skeleton after restructuring inside the hydrogel was confirmed by SEM. The band shifts between 3258 cm−1 and 3264 cm−1 clarified the presence of a large number of hydrogen bonds in physical and chemical cross-linked hydrogels. The robust structure of the hydrogel was confirmed by mechanical and thermal property measurements. Molecular docking techniques were used to help understand the bridging pattern between three raw materials and to assess the advantageous conformation, which demonstrate sorbitol is beneficial to improve the characteristics of textural hydrogel by the formation of hydrogen bonds, creating a denser network, structural recombination and new intermolecular hydrogen bonds between starch and sorbitol afforded considerably junction zones. Compared to ordinary starch-based hydrogels, eugenol-loaded starch-sorbitol hydrogels (ESSG) exhibited a more attractive internal structure, swelling properties, viscoelasticity. Moreover, the ESSG showed excellent antimicrobial activity for typical undesired microorganisms in foods.