Measurement Of Thermophysical Properties Research Articles

Three-sensor 3ω-2ω method for the simultaneous measurement of thermal conductivity and thermal boundary resistance in film-on-substrate heterostructures

Solid heterostructures composed of substrates and epitaxial films are extensively used in advanced technologies, and their thermophysical properties fundamentally determine the performance, efficiency, and reliability of the corresponding devices. However, an experimental method that is truly appropriate for the thermophysical property measurement of solid heterostructures is still lacking. To this end, a three-sensor 3ω-2ω method is proposed, which can simultaneously measure the thermal conductivities of the film and the substrate, along with the film-substrate thermal boundary resistance (TBR) in a single solid heterostructure without any reference samples, showing broad applicability for miscellaneous heterostructures with film thickness ranging from 100 nm to 10 μm. In this method, three parallel metal sensors with unequal widths and distances conforming to guidelines for the three-sensor layout design are fabricated on the sample surface, in which the two outer sensors serve as heaters and the middle sensor as a detector. The respective 3ω signals of the two heaters and the 2ω signal of the detector are measured, and then the thermophysical properties of the sample are fitted within 3D finite element simulations. To verify this method, two typical wide bandgap semiconductor heterojunctions, i.e., GaN on SiC (#SiC) and GaN on Si (#Si) with ∼2.3 μm GaN epilayers, are measured. The thermal conductivity of the GaN film, the thermal conductivities of the SiC and Si substrates, and the GaN/substrate TBRs are derived, exhibiting good agreement with the literature. The proposed method will provide a comprehensive solution for the thermophysical property measurements of various solid heterostructures.

Liquid Metal‐Carbon Fiber Thermocouple Array for Detection of Human Thermal Parameters

AbstractContinuous and accurate measurement of human thermophysical properties has become a vital research field in non‐invasive physiological diagnosis. However, traditional electronic devices have been greatly restricted due to the disadvantages of large volume, heavy weight, and mechanical rigidity. In this work, a kind of fiber‐structured LMs thermocouples composed of LMs fibers and nickel‐coated carbon fibers to solve the dilemma of good thermoelectric performance and sufficient flexibility is synthesized. With high thermoelectric properties as well as flexibility and knittability, the fiber‐structured LMs thermocouples can be assembled into a thermocouple array for multipoint temperature measurement in living organisms. While the nickel‐coated carbon fiber as the electric heating component further endowed the heating function for the fiber‐structured LMs thermocouples array, thus a linear heat source‐pulse heating method is successfully developed for qualitative/quantitative thermophysical parameters measurement (including thermal conductivity, thermal diffusivity, and blood perfusion rate). Collectively, the fiber‐structured LMs thermocouple array has shown promising prospects in human physiological measurement and thermophysical properties measurement.

Accessible ranges of turbulent and transitional flow in electromagnetic levitation experiments

Electromagnetic Levitation in reduced gravity has demonstrated great utility in the measurement of thermophysical properties and the study of solidification of metallic melts. Internal flow in the liquid metal samples is a critical parameter in many of these experiments. For example, turbulent flow in the sample prevents measurement of viscosity by the oscillating droplet method, as the measured damping of oscillations is a property of the flow and not of the fluid. In solidification, it has been demonstrated that internal flow changes the lifetime of the metastable phase in stainless steels by almost two orders of magnitude over the experimentally accessible range. For these experiments, the flow was quantified by CFD models; however, these models require as an experimental input whether the flow is laminar or turbulent. To date, the only study of the transition to turbulence in EML comes from experiments on the Space Shuttle in 1997 on MSL-1 TEMPUS on a palladium-silicon alloy. On each melting cycle, tracer particles reveal the laminar or turbulent nature of the flow. However, this phenomenon was only noticed and examined after the flight, so observations are available only for a very narrow range of conditions. As these results were the only ones available, they have been boldly extrapolated to conditions far from the original experiment. Furthermore, while evidence from measurements on germanium shows that the positioner alone can drive turbulent flow, there are no available measurements of the turbulent transition in positioner-dominated flows. On a more fundamental level, EML flows are constrained by the free surface of the drop, like the walls of internal flows. However, the free surface of the EML drop does not support shear stresses, unlike the walls in internal flows. Better quantification of the transition to turbulence in EML flows may lead to insights into the nature of turbulence and turbulent transition. Closing this gap requires a combination of experiments and models that will quantify the turbulent transition over as wide a range of experimental conditions as possible in ISS-EML. Modeling results are presented here; experiments are planned for ISS-EML Batch 4, estimated for 2024.

A quantitative comparison of thermophysical property measurement of CMSX-4� Plus (SLS) in microgravity and terrestrial environments

Density, thermal expansion coefficient, surface tension and viscosity of Ni-based CMSX-4� Plus have been measured for a range of liquid temperature by utilizing two Electrostatic levitation (ESL) facilities. Ground-based tests were conducted using the NASA MSFC ESL facility in Ultra High Vacuum and space-based tests were conducted using JAXA ELF in a 172 kPa Argon gas atmosphere. The measured values were compared to the available literature data from various other facilities. This study focuses on a detailed uncertainty analysis of the experimental data to measure the accuracy and precision of the measured properties using Guide to the expression of Uncertainty Measurement (GUM) principles. The findings from this study have been used to quantify the performance of the two ESL facilities.

Quantifying facility performance during thermophysical property measurement of liquid Zr using Electrostatic Levitation

Density, thermal expansion coefficient, surface tension and viscosity of liquid Zr at high temperatures were measured by oscillating droplet method in two Electrostatic Levitation (ESL) facilities. The ground-based tests at NASA MSFC ESL were conducted in vacuum and the space-based tests at JAXA ELF were conducted in Argon atmosphere with both results reported as a function of temperature. The accuracy and precision of each set of the measurement techniques has been reported using a detailed uncertainty analysis on both facilities. The uncertainties associated with each measurement were used to characterize performance for each facility. Zr samples processed in microgravity showed heavy influence of oxidation which lowered the natural frequency and thus significantly affecting the accuracy of surface tension measurement. The ground-based results are comparable to previously reported literature values.

Research on In Situ Thermophysical Properties Measurement during Heating Processes.

Biomass pyrolysis is an important way to produce biofuel. It is a chemical reaction process significantly involving heat, in which the heating rate will affect the yield and composition (or quality) of the generated biofuel. Therefore, the heat transfer inside the biomass pellets is important for determining the rate of temperature rise in the pellets. The accurate knowledge of the thermophysical properties of biomass pellets is required to clarify the process and mechanism of heat transfer in the particles and in the reactor. In this work, based on the transient thermoelectric technology, a continuous in situ thermal characterization method for a dynamic heating process is proposed. Multiple thermophysical properties, including thermal conductivity and volumetric heat capacity for corn leaves, are measured simultaneously within a heating process. In temperatures lower than 100 °C, the volumetric heat capacity slightly increases while the thermal conductivity decreases gradually due to the evaporation of water molecules. When the temperature is higher than 100 °C, the organic components in the corn leaves are cracked and carbonized, leading to the increase in the thermal conductivity and the decrease in the volumetric heat capacity against temperature.

Analysis of combustion chamber deposit growth on temperature swing thermal barrier coatings in a spark ignition engine

Temperature swing thermal barrier coatings (TBCs) have the potential to improve efficiency and performance through thermal management of the combustion chamber. However, the effects of combustion chamber deposits (CCDs) on the surface of the TBCs are unclear. Therefore, this paper analyzes the impact of CCD formation on a temperature swing TBC. A piston and a heat flux probe coated with a novel material are installed in a single-cylinder research engine at a low-load condition for 62.5 h to promote CCD growth. Every 12.5 h, the performance at a knock limited condition is assessed and thermophysical property measurements on the heat flux probe are performed. Net thermal efficiency increased by 0.4% absolute after 12.5 h relative to the baseline condition, but further CCD growth caused a dithering of efficiency between the 12.5 h and baseline points. The KLSA retarded consistently throughout this period. External property measurements with the coated heat flux probe showed an improvement in the thermophysical properties of the TBC/CCD layer.

Effects of doping on the thermophysical properties of Ag and Cu doped TiO2 nanoparticles and their nanofluids

A widely accepted method to improve the thermal performance of nanofluids is adding more particles to the fluid, which often causes higher viscosity and sedimentation risk. Therefore, alternative methods are required to create complex structures and improve the properties of particles to acquire similar or even better performance with a smaller amount. Doping is one of the promising methods, and this study examined the effects of doping rates (0.1 and 0.3 %) and materials (Ag and Cu) on the thermophysical properties of ethylene glycol-water-based nanofluids. Nanofluids were prepared with pure and Ag/Cu doped TiO2 nanoparticles at various concentrations (0.3 %, 0.5 %, 1 %, and 2) by mass. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), particle size distribution (PSD), Brunauer, Emmett, and Teller (BET) surface area analysis, and transmission electron microscopy (TEM). Thermophysical property measurements were carried out at a temperature range of 40 and 60 °C. Based on the results, all particles were spherical and had an anatase structure with an average particle size ranging from 6 nm to 8 nm. There was also a monodisperse distribution in the base fluid. At the highest doping rate (0.3 %) and lowest mass concentration (0.3 %) of Ag-doped particles, the maximum specific heat (3051.31 J/kgK) of the study was observed. Increasing concentration resulted in a maximum 48.2 % decrease in specific heat for nanofluids containing 0.1 % Cu particles. The thermal conductivity increased by 2.40 % with doping but by only 1.89 % with concentration. The highest increase in viscosity was determined as 75.21 % at 40 °C, depending on the concentration increase. Thus, the doping method presents better heat transfer performance without an undesirable increase in viscosity compared to increasing the concentration.

Experimental measurement of thermophysical properties of some commercial phase change materials (PCM) for air conditioning applications

This paper presents the measurement of liquid phase density, thermal diffusivity, thermal conductivity, and dynamic viscosity of five commercial PCM (RT2HC, RT5HC, OM05-P, OM08, CrodaTherm9.5) in the temperature range 2 − 30 °C. The density of RT2HC, RT5HC, OM05-P is 23-24% lower than water, that of OM08 is 6% higher than water and that of CrodaTherm9.5 is 14% lower than water. The thermal diffusivity of RT2HC, RT5HC, OM05-P is 22-24% lower than water, that of OM08 is around a half of water and that of CrodaTherm9.5 is 38-40% lower than water. The thermal conductivity of the five PCM is 72-74% lower than water. The dynamic viscosity of RT2HC, RT5HC, OM05-P and OM08 is 2 − 3 times higher than water, and that of CrodaTherm9.5 is from 7.4 to 8.3 times higher than water. The five PCM are expected to provide convective heat transfer performance significantly lower than water .

Nanomechanical Sensing Using Heater-Integrated Fluidic Resonators.

Micro/nanochannel resonators have been used to measure cells, suspended nanoparticles, or liquids, primarily at or near room temperature while their high temperature operation can offer promising applications such as calorimetric measurements and thermogravimetric analysis. To date, global electrothermal or local photothermal heating mechanisms have been attempted for channel resonators, but both approaches are intrinsically limited by a narrow temperature modulation range, slow heating/cooling, less quantitative heating, or time-consuming optical alignment. Here, we introduce heater-integrated fluidic resonators (HFRs) that enable fast, quantitative, alignment-free, and wide-range temperature modulation and simultaneously offer resistive thermometry and resonant densitometry. HFRs with or without a dispensing nozzle are fabricated, thoroughly characterized, and used for high throughput thermophysical properties measurements, microchannel boiling studies, and atomized spray dispensing. The HFR, without a doubt, opens a new avenue for nanoscale thermal analysis and processing and further encourages the integration of additional functions into channel resonators.

Thermophysical Property Measurements of Refractory Oxide Melts With an Electrostatic Levitation Furnace in the International Space Station

Due to their high melting temperatures and the risk of contamination from the crucibles, molten oxides which melting temperatures are above 2000 °C can hardly be processed using conventional methods. This explains that their thermophysical properties are very scarce. Containerless methods with gas flows have been developed and several thermophysical properties such as density, surface tension, and viscosity have been reported. However, the gas flow has detrimental side effects such as deformation of the sample and induction of internal flows in the molten sample, which affect the accuracy of the measurements. The electrostatic levitation furnace onboard the International Space Station (ISS-ELF), which utilizes the Coulomb force to levitate and melt samples in microgravity, has several advantages for thermophysical property measurements of refractory oxide melts. Levitation without a gas flow coupled to a reduced gravity environment minimizes the required levitation (positioning) force and reduces the deformation as well as the internal flow. This report briefly introduces the ISS-ELF facility and the thermophysical property measurement methods. The measured density, surface tension, and viscosity of molten Al2O3 are then presented and compared with the ones obtained by other methods. Finally, the measured data of refractory oxides whose melting temperatures are above 2,400 °C are summarized.

Thermo-physical properties measurements of hygroscopic and reactive material (zeolite 13X) for open adsorptive heat storage operation

The determination of the thermo-physical properties (density, specific heat capacity, and thermal conductivity) of hygroscopic and reactive solid materials, as those applied in sorption thermochemical heat storage systems, is not trivial. Lack of precision in the measurement and contradictory results make it difficult to enter these thermal parameters in the programs used for simulating the functioning and operating scenarios of thermochemical heat storage devices. For this reason, different techniques have been applied and compared in order to improve the accuracy of the measurement. In particular, there was a difference in thermal conductivity (about 30%) between the hot disc experiments and the others, as well as a higher dispersion of the experimental data (MAD > 19%). The same was found for specific heat capacity (MAD ≈14%). Hence, the transient hot disk method is not suitable for estimating thermal conductivity and the specific heat capacity of this type of material. Nevertheless, this technique enables a good estimation of the thermal effusivity. The thermal conductivity and the specific heat capacity were investigated by the hot wire method and by TG-DSC, respectively. A slight increase in specific heat with temperature was observed, but in the range of 70–95 °C, this value is constant at 913 J kg−1 K−1. The applied methodology was validated by comparing the experimental and calculated thermal effusivity values.

Measurement of thermophysical properties with nanomaterials on the Melting/Freezing characteristics of phase change material

In the present work, four formulations of the composite phase change materials (PCMs) were produced by adding 0.5 wt% of nanoparticles (NPs), and each formulation comprised one of the types of nanoparticles. Myristic acid was considered as the base material; 0.5 wt% of Al2O3, SiO2, CuO, and Ag were reckoned as the supporting materials. Al2O3, SiO2, CuO, and Ag NPs were synthesized and they were studied by different characterization techniques. The melting and freezing temperatures of myristic acid were determined in the range from 55.54 °C to 55.94 °C and from 48.42 °C to 48.71 °C, respectively. Likewise, the latent heats for melting and freezing were found to be 192.31 kJ/kg and 192.53 kJ/kg, respectively. The thermal properties of composite PCMs were evaluated with respect to weight fractions of NPs and thermal cycles. With nanomaterial dispersion, the laser flash analyzer (LFA) confirmed the thermal conductivity enhancement of myristic acid. The composite PCMs have faster melting and freezing times than pure PCMs, as stated in the results of this study.

A versatile interferometric technique for probing the thermophysical properties of complex fluids

Laser-induced thermocapillary deformation of liquid surfaces has emerged as a promising tool to precisely characterize the thermophysical properties of pure fluids. However, challenges arise for nanofluid (NF) and soft bio-fluid systems where the direct interaction of the laser generates an intriguing interplay between heating, momentum, and scattering forces which can even damage soft biofluids. Here, we report a versatile, pump-probe-based, rapid, and non-contact interferometric technique that resolves interface dynamics of complex fluids with the precision of ~1 nm in thick-film and 150 pm in thin-film regimes below the thermal limit without the use of lock-in or modulated beams. We characterize the thermophysical properties of complex NF in three exclusively different types of configurations. First, when the NF is heated from the bottom through an opaque substrate, we demonstrate that our methodology permits the measurement of thermophysical properties (viscosity, surface tension, and diffusivity) of complex NF and biofluids. Second, in a top illumination configuration, we show a precise characterization of NF by quantitively isolating the competing forces, taking advantage of the different time scales of these forces. Third, we show the measurement of NF confined in a metal cavity, in which the transient thermoelastic deformation of the metal surface provides the properties of the NF as well as thermo-mechanical properties of the metal. Our results reveal how the dissipative nature of the heatwave allows us to investigate thick-film dynamics in the thin-film regime, thereby suggesting a general approach for precision measurements of complex NFs, biofluids, and optofluidic devices.

Experimental Analysis of Heat Transfer by Using Nanofluid and Impact of Thermophysical Properties

The scope of the project is to analyse the heat transfer behaviours by using shell and tube heat exchangers and measurements of various thermophysical properties of carbon nanotube nanofluid. The nanofluid is created using different volume fractions at different operation temperatures. The research focuses on theoretical and experimental research on CNT nanofluids, with the goal of improving thermophysical parameters such as thermal conductivity, specific heat, and viscosity. The thermophysical characteristics of CNTs were investigated using this theoretical method. Various tests were carried out to investigate the thermophysical qualities, and they were found to have an impact. The improved characteristics of carbon nanotubes (CNTs) have the potential to save energy and reduce CO2, NO2, and SO2 emissions in industrial settings. Improving heat exchange performance in the thermal sector would result in a high heat-to-power conversion efficiency. Nanofluids can considerably enhance critical heat flux (CHF) in heat transfer systems.

Effects of concave curvature on the formation and propagation of capillary wave induced by electrowetting-on-dielectric

Capillary-wave propellers (CWPs) based on the phenomenon of electrowetting-on-dielectric (EWOD) have shown great potential for floating-object propulsion, heat-transfer enhancement, and fluid thermophysical property measurement. However, the small amplitude of the EWOD-induced capillary-wave limits the performance of the CWP in practical applications. Herein, a CWP with a concave curvature is proposed to enlarge the capillary-wave amplitude. The formation and propagation of the capillary wave are visualized by using a high-speed camera and a free-surface synthetic schlieren method. The wave amplitude and wave propagation are modeled theoretically. The effects of the concave curvature and the frequency of the electrical signal are investigated, and the results show that the concave curvature increases the wave amplitude, velocity vector, and wave intensity as compared with flat EWOD units. In addition, the results show that 20 Hz electrical signals are favorable for pursuing large wave energy density. The underlying mechanism for increasing the wave energy via concave CWPs is revealed experimentally and explained theoretically. The proposed concave CWP is helpful for increasing the propulsion speed of small-scale floating objects and is promising for improving the performance of CWPs in other applications.

Tuning thermal and electrical properties of MXenes via dehydration.

Recently, MXenes (a class of two-dimensional transition metal carbides) have attracted great attention in various applications such as humidity sensors, owing to their unique electrical and thermal properties. However, previous studies of MXenes mostly focus on their humidity-sensing characteristics such as the mechanical response, and only few reports on their electrical and thermal response are available. Herein, we present novel transient electrothermal experiments to demonstrate that a transition from a negative to a positive resistance-temperature relationship can take place when the MXene sample becomes fully dehydrated. This surprising and unusual phenomenon was elucidated through non-equilibrium molecular dynamics simulations and attributed to water absorption/desorption onto the chemically active MXene surface. A linear relationship was also found between electrical/thermal properties and environmental humidity, which could be related to water adsorption on the surface of the MXene sensor. We further decomposed the total measured thermal conductivity and found that phonons were the dominant thermal carriers in the MXene sample. The main breakthrough of this work is the discovery of the unusual resistance-temperature relationship, which should be applicable to the design of MXene-based sensors for various applications.

Upgrading the PLINIUS platform toward smarter prototypic-corium experimental R&D

In the recent years, CEA Cadarache PLINIUS prototypic corium platform has been upgraded: more powerful induction generator for e.g. MCCI experiments, development of thermitic melting, e.g. for new corium spreading tests in VULCANO, new MERELAVA facility for corium flooding, new VITI setups for thermophysical property measurements, KROTOS FCI test with full depth X-ray visualization of water pool. Main features of these facilities are described. Designs for further improvements such as the new FUJISAN and VITAE setups for characterizations of the aerosol released during prototypic fuel debris cutting, as well as the design of STROMBOLI test section for studying Lower Head pool stratification inversion evolution are also presented.

Measurement and study of thermophysical properties of nanofluids with carbon nanotubes

This article is devoted to the study of the thermophysical properties of nanofluids with single-walled and multi-walled carbon nanotubes (CNT). Their weight concentration varied from 0.05 to 0.2%. Nanofluids, based on ethylene glycol and water, were studied. Dispersants were also used. The diffusion of CNT had been systematically investigated by the method of dynamic light scattering and their effective hydrodynamic dimensions were determined. The rheology and viscosity of all nanofluids were studied. It is shown that nanofluids are either pseu-doplastic or viscoplastic. Their rheology changes with increasing CNT concentration and temperature. However, in all cases, the viscosity of nanofluids with single-walled CNTs is signifi-cantly higher than that of nanofluids with multi-walled CNTs. In the last part, the electrical conductivity of all these nanofluids and the dispersants effect on it are investigated.

Development of High Temperature Multi-Layer Laser Flash Artefacts

Delamination of the interlayers of multi-layer systems can cause a degradation in functionality, stability and life span of that system. This is even more pertinent for systems at high temperature. Laser flash analysis (LFA) has long been used for thermophysical properties measurements at high temperatures. Multi-layer reference artefacts, with and without, debonded regions are required for validating the thermal characterisation of such systems using LFA. Although some high-temperature bulk candidate reference materials were developed and studied, e.g. in the European Metrology Research Programme (EMRP) funded Joint Research Project (JRP) ENG08 Metrofission, they were not able to meet the requirements for validating thermal measurements of multi-layer systems using LFA. In the European Metrology Programme for Innovation and Research (EMPIR) funded JRP 17IND11 Hi-TRACE project, the National Physical Laboratory is developing multi-layer reference artefacts, including both fully bonded and partially de-bonded systems for validating thermal characterisation of multi-layer systems at temperatures from room temperature to above 1000 °C using LFA. This paper details the methodology of production, measurement and validation of isotropic graphite and hafnium based multi-layer systems with, and without, partial debonding. Reproducibility, thermal stability and sensitive parameters concerning the thermal response of the artefacts will be discussed, with recommendation on the usage criteria as LFA multi-layer reference artefacts.