Measurement Of Thermal Effusivity Research Articles

Thermal Effusivity Assessment of Sportswear Fabrics in the Dry State: Stacked and Air-Hoop Methods

Abstract In recent years, thermal effusivity, a property that describes the warm or cool touch perception, has gained significant attention in the apparel industry as it contributes to human thermophysiological comfort. The current study aims to explore the thermal effusivity of 27 sportswear fabrics, including woven and knitted structures with various fiber contents, using the stacked method (according to ASTM D7984-21, Standard Test Method for Measurement of Thermal Effusivity of Fabrics Using a Modified Transient Plane Source (MTPS) Instrument) and a modified air-hoop method. The results obtained revealed that the pressure range specified in ASTM D7984-21 (10–50 kPa) may cause fabric compression, resulting in the measurement of a material-based thermal effusivity rather than the fabric thermal effusivity. A pressure of 1 kPa was found to be more appropriate for obtaining accurate measurements of sportswear fabrics without altering their three-dimensional structure. Furthermore, a strong correlation was observed between the stacked and air-hoop methods for fabrics with thicknesses close to or greater than 0.4 mm. The air-hoop method simulates the configuration when the fabric is worn as part of a garment. The new knowledge provided by this research will enhance the accuracy of the thermal effusivity measurement of sportswear fabrics. It will contribute to the development of more comfortable fabrics considering realistic garment use scenarios.

Quantitative thermal investigation of a fayalite particle and a Si-rich layer in oxide scale formed on steel

Fayalite (Fe2SiO4) is a major component of olivine and is often formed in the surface oxide layer (oxide scale) on steel plates owing to its high-temperature oxidation. The thermal conductivity of the oxide scale and its constituents, including fayalite, is essential for controlling the cooling rate of hot steel plates. Therefore, this study uses modulated thermoreflectance microscopy to determine the thermal effusivity/conductivity of fayalite particles with diameters smaller than 180 μm because the sample commercially available is such a small size. This thermal optical microscopy enables the measurement of thermal effusivity for small areas, such as 10 μm. The thermal effusivity and conductivity were found to be 4.1 ± 0.2 kJs-0.5K-1m-2 and 6.0 ± 0.5 Wm-1K-1, respectively. These values are representative of the bulk value. Additionally, the thermal conductivity of fayalite is shown to be higher than that of wüstite (Fe1-xO), which is the main component of the oxide scale. The oxide scale formed on the thick steel plate comprises a Si-rich layer, a wüstite layer, and a magnetite layer. Furthermore, the Si-rich layer comprises fayalite, wüstite, and pores. The effective thermal conductivity of the Si-rich layer was calculated by observing the oxide scale formed on the steel plate. The low thermal conductivity of the Si-rich layer indicates that the thermal conductivity of the layer is strongly affected by the porosity of the oxide scale. Furthermore, although the Si-rich layer is thin, it significantly contributes to the heat resistance of the oxide scale.

Development for High Spatial Resolution Thermal Effusivity Measurement Method and High Functional Thermal Diffusivity Measurement Method

Development for High Spatial Resolution Thermal Effusivity Measurement Method and High Functional Thermal Diffusivity Measurement Method

Determination of Thermal Diffusivity/conductivity of Oxide Scale Formed on Steel Plate by Laser Flash Method through Thermal Effusivity Measurement by Transient Hot-strip Method

Determination of Thermal Diffusivity/conductivity of Oxide Scale Formed on Steel Plate by Laser Flash Method through Thermal Effusivity Measurement by Transient Hot-strip Method

Quadrupole modelling of dual lock-in method for the simultaneous measurements of thermal diffusivity and thermal effusivity

The simultaneous measurement of thermal diffusivity and thermal effusivity based on the temperature wave analysis (TWA) is proposed by introducing the dual lock-in temperature sensor with a photo-thermal ac heat source. The thermal effect from each component in the multilayered experimental system is simulated by the quadrupole modeling adopted to the pure periodic heating of the temperature wave. The frequency dependency of the thermal effect from the thermal contact resistance and capacitance in the sensor were analyzed and minimized by taking the optimal frequency range of the temperature wave. The proposed method is applied to examine the nematic-isotropic phase transition of the liquid crystal 4′-(pentyloxy)-4-biphenyl carbonitrile (5OCB). The results were compared with the previous results measured with a single sensor and the advantage of the dual lock-in temperature sensor was demonstrated.

Thermophysical Characterization of an Insulating Bio-material Based on the Macerate of ''Néré'' (<i>Parkiabiglobosa</i>) Pods and Cow Dung

This work concerns the thermophysical characterization of a bio-eco-material made from cow dung and the macerate of nere pods. To achieve this, chemical tests based on tannin concentration determination of four different solutions of nere pods (60 g.l-1; 120 g.l-1; 180 g.l-1 and 240 g.l-1) were prepared at 100°C, then brought to the boil for 5 minutes. After three different maceration times (6 h; 24 h and 48 h), the analysis of the solutions obtained using a spectrometer made it possible to select the solutions of 120 g.l-1 and 180 g.l-1 which offer best tannin concentrations in 24 hours, necessary for making test pieces. Thermal tests based on thermal effusivity and thermal conductivity measurements were then carried out in transient mode, with hot strip method. In order to compare the thermal performance of developed eco-material with that of ordinary insulators, the thermophysical properties of plywood and plaster were also measured. The results obtained showed that for the two dosages of 120 g.l-1 and 180 g.l-1, the thermal effusivity of eco-insulator varies from 247.732 J.K-1.m-2.s-0,5 to 270.732 J.K-1.m-2.s-0,5 respectively and the thermal conductivity from 0.082 W.m-1.K-1 to 0.080 W.m-1.K-1. For the same dosages, the thermal diffusivity varies from 1.106.10-7 m².s-¹ to 0.881.10-7 m².s-¹ respectively. A comparative study has shown that the eco-material developed and tested offers better insulating power due to its relatively weak thermophysical properties compared to ordinary insulating materials, namely plaster and plywood.

Thermal parameters of roofing slates from Czech Republic

Thermal performance of building materials is an important parameter from the point of view of energy consumption for heating buildings, which is obviously related to environmental protection standards. Thermal parameters of roofing slates were measured for samples from two different formations in the Czech Republic. These were rocks of lower Carboniferous Culm facies of Moravice Formation and Silesian Unit of Flysch Moravian-Silesian Carpathians. Thermal conductivity and thermal effusivity measurements were performed with use of TCi analyser. Thermal parameters were obtained in parallel and perpendicular direction to the bedding in rocks. Thermal conductivity of the Moravian slates in the direction perpendicular to the bedding ranges from 1.43 to 1.79 W m−1 K−1, while for samples from Carpathian region this parameter ranges from 1.99 to 3.15 W m−1 K−1. High values of thermal conductivity correlate to higher quartz content in the rocks. The measured thermal parameters (conductivity, effusivity, diffusivity) are strongly depending on the direction of measurement. Thermal conductivity of analysed rocks increases along with increase in temperature. The increase in thermal conductivity value is more significant in case of Moravian slates. In practice, the obtained results indicate that the traditional building material, such as roofing slates, shows better insulation properties at lower temperatures, while in conditions of strong sunlight the temperature conductivity increases. In case of roofing slates, which tend to be highly anisotropic, the essential information is the direction of thermal parameters measurement. Slates, due to their specific texture, are characterized by a very high thermal anisotropy coefficient.

The effective temperature at which fingertips sense thermal effusivity and the bias of measurements at room temperature

Thermoreceptors in the fingertips sense the temperature drop upon contact with an object and in that way its thermal effusivity.But, at which effective object temperature? That is the question that this article answers by perturbation analysis for slightly temperature dependent thermal properties.How much deviate thermal effusivity measurements at room temperature from fingertip measurements at said effective object temperature? This question is also answered by perturbation analysis.The bias may be up to 7% using nearly isothermal measurement methods and up to around 19% using fingertip-mimicking measurement methods for airy materials like wool.Rewriting the temperature model reveals a felt delay and its dependency on the thermal contact resistance between fingertip and object.

Complex Thermophysical Analysis of the Samples of Rocks Based on the Data of Measurements of Thermal Effusivity

We propose a new procedure for the complex evaluation of thermal properties of rocks based on the data of measurements of the thermal effusivity of samples and the numerical analyses of the volumetric heat capacity according to the mineral composition of the rock. The thermal effusivity is measured under the conditions of periodic heating of the surface of a reference plate operating in contact with the investigated sample. The thermal conductivity and thermal diffusivity are computed according to the estimates of the thermal effusivity and heat capacity. The equations for the errors of the thermophysical analysis are also presented.

Thermal effusivity measurements of thermal insulators using the photopyroelectric technique in the front configuration

In the photopyroelectric (PPE) technique in the front configuration one surface of a pyroelectric sensor is illuminated by a modulated laser beam, whereas the other surface is in contact with the sample under study. A frequency scan of the PPE signal allows to measure the thermal effusivity of liquids. Recently, it has been applied to solid samples, by taking into account the effect of the thin grease layer used to guarantee the thermal contact between sample and sensor. In this work, we extend this method to address the challenge of measuring the effusivity of thermal insulators accurately. We have developed a complete model of the PPE signal generation, including heat losses by convection, radiation and conduction to the surrounding gas. Besides, very thin pyroelectric sensors are used since they enhance the sensitivity of the PPE signal to the sample effusivity. Moreover, the sample is placed directly in contact with the sensor, without using any coupling grease, to avoid polluting porous samples. PPE measurements on several thermal insulators (paper, cork, wood and foam) indicate that this method is well suited to retrieve the thermal effusivity of insulators precisely.

Joint thermophysical analysis of rock samples based on thermal effusivity measurements

Joint thermophysical analysis of rock samples based on thermal effusivity measurements

Thermal effusivity measurement of conventional and organic coffee oils via photopyroelectric technique

In this work, oil samples extracted from organic and conventional coffee beans were studied. A fatty acids profile analysis was done using gas chromatography and physicochemical analysis of density and acidity index to verify the oil purity. Additionally, Mid-Infrared Fourier Transform Photoacoustic Spectroscopy (FTIR-PAS) aided by Principal Component Analysis (PCA) was used to identify differences between the intensities of the absorption bands related to functional groups. Thermal effusivity values between 592±3 and 610±4Ws1/2m−2K−1 were measured using the photopyroelectric technique in a front detection configuration. The acidity index was between 1.11 and 1.27% and the density changed between 0.921 and 0.94g/mL. These variables, as well as the extraction yield between 12,6 and 14,4%, showed a similar behavior than that observed for the thermal effusivity, demonstrating that this parameter can be used as a criterion for discrimination between oil samples extracted from organic and conventional coffee beans.

Self-normalized inverse photopyroelectric technique with viscous front window for thermal effusivity measurements in liquids

In this paper, the front detection (also called inverse configuration) photopyroelectric method for thermal effusivity measurement in liquids is improved by adding a viscous liquid to the front face of the pyroelectric sensor, on which the intensity modulated excitation light beam impinges, while the sample is attached to the rear side of the sensor. This viscous liquid will act as an optical transparent window. This configuration avoids problems related with the piezoelectric contribution to the photopyroelectric signal at high modulation frequencies that can be present in conventional approaches due to thermoelastic waves generated in the heated sample or by thermally induced deformations of the detector material itself. The theoretical and experimental principles behind the proposed method are presented and its usefulness is demonstrated with measurements on test samples.

Modulation calorimetry in diamond anvil cells. II. Joule-heating design and prototypes

Part I shows that quantitative measurements of heat capacity are theoretically possible inside diamond anvil cells via high-frequency Joule heating (100 kHz–10 MHz), opening up the possibility of new methods to detect and characterize transformations at high-pressure such as the glass transitions, melting, magnetic orderings, and the onset of superconductivity. Here, we test the possibility outlined in Part I, using prototypes and detailed numerical models. First, a coupled electrical-thermal numerical model shows that specific heat of metals inside diamond cells can be measured directly using ∼1 MHz frequency, with <10% accuracy. Second, we test physical models of high-pressure experiments, i.e., diamond-cell mock-ups. Metal foils of 2–6 μm-thickness are clamped between glass insulation inside diamond anvil cells. Fitting data from 10 Hz to ∼30 kHz, we infer the specific heat capacities of Fe, Pt, and Ni with ±20%–30% accuracy. The electrical test equipment generates −80 dBc spurious harmonics, which overwhelm the thermally induced harmonics at higher frequencies, disallowing the high precision expected from numerical models. An alternative Joule-heating calorimetry experiment, on the other hand, does allow absolute measurements with <10% accuracy, despite the −80 dBc spurious harmonics: the measurement of thermal effusivity, ρck (ρ, c, and k being density, specific heat, and thermal conductivity), of the insulation surrounding a thin-film heater. Using a ∼50 nm-thick Pt heater surrounded by glass and 10 Hz–300 kHz frequency, we measure thermal effusivity with ±6% accuracy inside the sample chamber of a diamond anvil cell.

Thermo-mechanical characterization of a building material based on Typha Australis

This paper is a contribution to the valorization of Typha Australis as building material. To do this, the crushed fibers of Typha have been agglomerated using clay as binder. The weight percentage of binder is found to be at least 75% to obtain stable materials. The influence of binder content on mechanical and thermal insulation properties was examined. The mechanical properties were evaluated by using a mechanical press. The measurements of thermal effusivity and thermal conductivity of samples have been performed using the transient hot-plate method. Compression and tensile strengths respectively varies from 0.279 to 0.796MPa and from 0.340 to 0.969MPa when the weight percentage of binder range from 77–85%. This values have a strong linear correlation with the weight percentage of binder. The thermal conductivity of dry materials varies from 0.117 to 0.153 W.m−1.K−1 while the thermal effusivity rises from 228.9 to 300.0 J.m−2.°C−1.s−12. The results show that the thermal conductivity and thermal effusivity increases with increasing moisture content of materials.

Simultaneous measurements of anisotropic thermal diffusivity and thermal effusivity of liquid crystals using temperature wave analysis method

Simultaneous measurements of anisotropic thermal diffusivity and thermal effusivity in the phase transition of the liquid crystal 4′-(pentyloxy)-4-biphenyl carbonitrile (5OCB), Cry–53–N–68–Iso, are demonstrated using the temperature wave analysis method. A detailed calibration procedure for determining thermal diffusivity (α), thermal effusivity (e), thermal conductivity (λ), and heat capacity per unit volume (Cpρ) is proposed utilizing hexaethylene glycol monododecyl ether (C12E6) as a calibration material, the heat capacity of which is precisely determined using a calorimetric method.

Thermal effusivity measurement based on analysis of 3D heat flow by modulated spot heating using a phase lag matrix with a combination of thermal effusivity and volumetric heat capacity

The study goal was to establish a standard industrial procedure for the measurement of thermal effusivity by a thermal microscope (TM), using a periodic heating method with a thermoreflectance (TR) technique. To accomplish this goal, a working group was organized that included four research institutes. Each institute followed the same procedure: a molybdenum (Mo) film was sputtered on the surface of Pyrex, yttria-stabilized zirconia (YSZ), alumina (Al2O3), Germanium (Ge), and silicon (Si) samples, and then the phase lag of the laser intensity modulation was measured by the resultant surface temperature. A procedure was proposed to calibrate the effect of 3D heat flow, based on the analytical solution of the heat conduction equation, and thermal effusivity was measured. The derived values show good agreement with literature values. As a result, the TM calibration procedure can be recommended for practical use in measuring the thermal effusivity in a small region of the materials.

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

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

Note: Photopyroelectric measurement of thermal effusivity of transparent liquids by a method free of fitting procedures.

In a recent paper published in this journal [R. Ivanov et al., Rev. Sci. Instrum. 86, 064902 (2015)], a methodology free of fitting procedures for determining the thermal effusivity of liquids using the electropyroelectric technique was reported. Here the same measurement principle is extended to the well-known photopyroelectric technique. The theoretical basis and experimental basis of the method are presented and its usefulness is demonstrated with measurements on test samples.

Photopyroelectric Technique, in the Thermally Thin Regime, for Thermal Effusivity Measurements of Liquids

A photopyroelectric methodology using pyroelectric devices in the thermally thin regime, for the measurement of the thermal effusivity of liquids, is described. A commercial buzzer, taking advantage of the pyroelectric activity of the ceramic material (PZT in this case), is used to achieve this goal. Equivalence for thermal effusivity measurements between this photopyroelectric methodology and a previously reported photoacoustic technique, in the front configuration, is established. The thermal effusivity of six liquids was measured using this device, and very good agreement was found with corresponding values reported in the literature.