Quick Thermal Conductivity Meter Research Articles

Electrical resistivity and thermal conductivity properties of graphene‐coated woven fabrics

ABSTRACTIn this study, it was aimed to develop electrically and thermal conductive textiles surfaces. Pretreated polyester fabrics were coated with nano graphene powders at different concentration rates (50, 100, and 200 g/kg) by knife over roll technique. Electrical resistivity, thermal conductivity, thickness and mass per unit area measurements, bending rigidity, and abrasion resistance tests of coated fabrics were performed. Surface resistivity measurements of coated fabrics were made according to ASTM D 257 standard with Keithley 8009 Resistivity Test Fixture. Surface electrical resistivity values of coated fabrics decreased with increasing concentration rates. Of note, 2.53 × 104 Ω/sq surface resistivity value was obtained at 200 g/kg graphene concentration rate. Thermal conductivity measurements of coated fabrics were made according to JIS R 2618 standard with Quick Thermal Conductivity Meter (QTM‐710). Thermal conductivity property of fabrics improved depending on graphene concentration. The highest thermal conductivity value (0.4243 W/mK) was obtained at 200 g/kg graphene concentration rate. One of the most important results of the study was that a maximum weight loss of 0.40% was observed in the abrasion resistance test even after 100 000 cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48024.

Analyses of Mechanical Properties of By-products for Development of Livestock Feed Bioreactor

Abstract.Research on the utilization of by-products for alternative feed production has been undertaken to reduce the cost of breeding livestock especially in East Asia where there is high dependency on grains. Most studies, however, have focused on their properties. By-products have a wide range of moisture content (MC). Anaerobic fermentation is usually adopted as a processing method to prevent deterioration, decomposition, and acidification during the transportation and storage processes. As a preceding study for developing a storage and fermentation system, the objective of this study was to analyze the mechanical characteristics of by-products. Geometric, physical, and rheological characteristics were examined using particle testing methods. Heat transfer coefficient and specific heat of by-products were determined using quick thermal conductivity meter. An extremely high uniformity coefficient of between 2.30 and 3.29 for the mixed by-products was recorded with a static repose angle ranging from 32.3° to 46.6°. The adhesive force increased when materials high in moisture were mixed. The heat transfer coefficient was in the range of 0.1244 to 0.2774 W/m·K and specific heat was between 307.8 and 594.3 J/g. Mechanical characteristics of by-products for the development of bioreactor were examined and reported. Keywords: By-products, Fermentation, Livestock feed, Mechanical characteristics, Storage.

The thermal properties of mortars modified by the effect of combining polymers and SCMs

The thermal performance of the building materials is relevant to any use of composite materials, especially in relation to constructions where it is desirable to have high specific heat, low thermal conductivity and slight or no decrease of stiffness upon heating. The thermal coefficients of composite mortars made up of mixtures of combining styrene polyacrylic SPA Latex and supplementary cementitious materials SCMs were measured at different ages (7, 14, 28, 60, 90 and 120 days). So, in order to determine the thermal conductivity, the calorific capacity and thermal diffusivity of SCM-modified mortars, it seemed interesting to evaluate the influence of adding the SPA Latex (0.5%, 1% and 2%w) on the properties of these mortars when exposed to a quick thermal conductivity meter based on standard ISO 8302-91. The highest thermal conductivity of 1.51 W.m-1.K-1 was observed with the samples containing only plain cement. It decreased with the increase of SPA latex percentages. The lowest values of thermal coefficients were obtained with the samples prepared with SPA polymer at 2% and SCMs. In this way, the results obtained highlight the beneficial effect of combining SPA polymer and SCM materials as thermal insulation in comparison with other insulation materials. In fact, using SCMs as cement substitutes reduces the energy consumption. These composite mortars address problems related to environmental pollution by CO2 emissions, and can be recommended as materials for energy efficiency in buildings.

The thermal properties of mortars modified by the effect of combining polymers and SCMs

The thermal performance of the building materials is relevant to any use of composite materials, especially in relation to constructions where it is desirable to have high specific heat, low thermal conductivity and slight or no decrease of stiffness upon heating. The thermal coefficients of composite mortars made up of mixtures of combining styrene polyacrylic SPA Latex and supplementary cementitious materials SCMs were measured at different ages (7, 14, 28, 60, 90 and 120 days). So, in order to determine the thermal conductivity, the calorific capacity and thermal diffusivity of SCM-modified mortars, it seemed interesting to evaluate the influence of adding the SPA Latex (0.5%, 1% and 2%w) on the properties of these mortars when exposed to a quick thermal conductivity meter based on standard ISO 8302-91. The highest thermal conductivity of 1.51 W.m-1.K-1 was observed with the samples containing only plain cement. It decreased with the increase of SPA latex percentages. The lowest values of thermal coefficients were obtained with the samples prepared with SPA polymer at 2% and SCMs. In this way, the results obtained highlight the beneficial effect of combining SPA polymer and SCM materials as thermal insulation in comparison with other insulation materials. In fact, using SCMs as cement substitutes reduces the energy consumption. These composite mortars address problems related to environmental pollution by CO2 emissions, and can be recommended as materials for energy efficiency in buildings.

Experimental Evaluation of Thermal Performance and Durability of Thermally-Enhanced Concretes

The thermal performance and durability of the thermally-enhanced concrete with various insulating materials were evaluated through a series of tests. Three types of insulating materials—diatomite powder, hollow micro-spheres, and a micro-foam agent—were used for both normalweight aggregate concrete (NWAC) and lightweight aggregate concrete (LWAC). The thermal conductivity was measured by two different test methods: quick thermal conductivity meter (QTM) and guarded hot wire (GHW) methods. Then, the results were compared with each other. All insulating materials used in this study proved their ability to reduce the thermal conductivity. Additionally, it can be found that the trend of a decrease in air-dry density is similar to that of thermal conductivity of thermally-enhanced concrete. Additional thermal transmission tests with seven large-scale specimens were conducted by using the calibrated hot box (CHB). However, from this tests, it was seen that thermal transmission reduction for tested specimens were not large compared to the thermal conductivity reduction measured by QTM and GHW, due to multiple heat transfer. To examine the durability of thermally-enhanced concretes, accelerated carbonation and freeze-thaw cycle tests were conducted. From the results, it can be found that the thermally-enhanced concrete shows good freeze-thaw resistance. However, the carbonation rates of the concretes increased rapidly and additional methods to improve the carbonation resistance should be considered.

A fractal approach to determine thermal conductivity in cement pastes

This paper presents a preliminary work to evaluate the thermal conductivity performance in pure and blended cement pastes with fly ash, slag and silica fume. The thermal conductivity of cement pastes cured in saturated and dry status with different hydration ages are also measured and predicted by quick thermal conductivity meter (QTM) and innovative non-contact impedance measurement (NCIM) based on a newly proposed fractal model. Besides, a corresponding simulation of fractal-like network is developed to evaluate the influences of pore structure parameters, intrinsic thermal conductivity coefficients of solid and water or gas phase on thermal conductivity performance of cement pastes.

Determination of the relative thermal conductivity of solid samples by X-ray diffraction device

The thermal conductivity (TC) of metal and rock samples was determined, under ambient conditions, using standard X-ray diffraction equipment in which only the diffractometer sample holder had been modified from the original. As the method is comparative, standard reference materials were used: a copper standard for the analysis of metals and marble for the rock specimens. The marble was analyzed beforehand using a quick thermal conductivity meter QTM. In experimental measurements of TC the mean reproducibility value appears to be about 4% while the accuracy is about 5% for the examined rocks, and better for metals.

The Transverse Thermal Conductivity Coefficients of Some Hardwood Species Grown in Turkey

Thermal conductivity values for ash, oak, silver wattle, poplar, and beech were measured. Thermal conductivity coefficients of the wood species were determined for radial and tangential directions at four different moisture conditions, ranging from 0 to 22 percent moisture content (MC). Equations predicting thermal conductivities of the wood species according to the MC are proposed in the tangential and radial directions. The thermal conductivity test was performed with a quick thermal conductivity meter based on the ASTM C1113-99 hot-wire method, and measurements were carried out at a room temperature of 20°C to 24°C. The effect of density and porosity on thermal conductivity was also investigated. Results showed the behavior of all wood species studied is quantitatively similar. Thermal conductivity increased with increasing MC. Tangential thermal conductivity values within the MC range of 0 to 22 percent changed from 0.089 to 0.147 W/m-K for poplar, 0.127 to 0.222 W/m-K for beech, 0.113 to 0.202 W/m-K for ash, 0.142 to 0.290 W/m-K for silver wattle, and 0.130 to 0.219 W/m-K for oak. Tangential thermal conductivity was similar to radial thermal conductivity. Radial thermal conductivity was 1.08 times tangential thermal conductivity for poplar, 1.01 times for beech, 1.06 times for ash, 0.95 times for silver wattle, and 1.03 times for oak, respectively. The data are useful when calculating the energy required to kiln-dry lumber and predicting the thermal insulating qualities of log homes made from the species.

Evaluation of Thermal Conductivities of Printing Papers Using a Thermal Transfer Printer

The printing method of the thermal transfer printer is to push an ink ribbon that is heated and melted by a thermal head to a printing paper, and transfer the ink to desired positions on the paper. If the heating by the thermal head is not sufficient, the ink cannot be melted and cannot be transferred to the paper. Moreover, even if the heating is excessive, a high quality print cannot be done, because an excess amount of ink will be transferred to the paper. The heat generated by the thermal head is transmitted to the printing paper through the ink ribbon. Thus the thermal conductivity of the printing paper affects the temperature rise of the ribbon and as a result printing quality. The thermal conductivity of the paper is commonly measured with a quick thermal conductivity meter. However the printing paper is too thin for the measurement. A new method of evaluating the thermal conductivity of the printing paper using the thermal transfer printer was proposed.

A comparison of the divided-bar and QTM methods of measuring thermal conductivity

Reliable determinations of thermal conductivity ( K) are essential for any evaluation of terrestrial heat flow. In an extension and confirmation of an earlier study (Sass, 1984a), operational requirements of the relatively new and easy-to-use and maintain QTM (Quick Thermal Conductivity Meter) technique are compared and contrasted with those of the well established divided-bar method. Analysis of QTM experimental data leads to several recommendations: most importantly, (a) at least 5–6 measurements per sample for isotropic rocks (twice as many for anisotropic rocks)–limiting sample processing to no more than 2 per hour—and (b) slab dimensions of at least 20 × 50 × 70 mm (if K < 3 W/mK ) to 30 × 70 × 70 mm (if K > 5 W/mK ). For saturated specimens, experimental uncertainty (±5%) and reproducibility (±5%) are greater than for the divided-bar apparatus (±4 and ±2%, respectively). Conductivity measurements obtained with the two techniques for 15 dry and water-saturated samples ranging in conductivity from 0.6 to 5.4 W/mK have been compared. For saturated samples, agreement is excellent, with divided-bar values on average several percent greater than QTM values; this discrepancy is most probably related to the different conductivity standards used with the two types of apparatus. Systematic differences of 10–20% arising at conductivities greater than 5 W/mK require further study. For dry samples, divided-bar values are 10% greater on average than QTM values; this difference is attributable to the application in the divided-bar method of an axial load, the principal effect of which is to close low-conductivity air-filled cracks. The need for establishing a uniform international conductivity reference standard is emphasized.

Heat flow in northern Thailand

One hundred and two geothermal gradients have been obtained from water wells and mineral and oil prospecting holes in northern and northeastern Thailand. The geothermal gradients vary in the broad range of 8–95 mK/m. Two hundred and sixty-one rock samples and two hundred and nine rock-core samples of various types and formations were collected for the thermal conductivity measurement. A Quick Thermal Conductivity Meter (QTM) was used for the measurements both in wet and dry states: the latter values represent the in-situ condition and, therefore, were used for the heat flow determinations. Heat flow values have been obtained by the multiplication of the geothermal gradients and the thermal conductivity values of rocks which represented the lithology. The heat flow values obtained ranged in a broad interval of 17–320 mW/m 2. Using all stations as check points a simple heat flow density pattern for northern Thailand was proposed, which clearly shows four regions with high heat-flow (over 100 mW/m 2): the Fang oil fields, the San Kamphaeng geothermal area, Mae Sot and the western margin of Khorat plateau (Phetchabun province).

On the thermal conductivity of low-porosity crystalline rocks

Measurements by a Quick Thermal Conductivity Meter on dry and water-saturated granitic samples at room temperature are reported. For a porosity of 0.8% the difference between dry and water-saturated conductivities amounts to 30%. The measured conductivities are in good agreement with values calculated for a pore configuration model based on interconnected crack-type pores. Rapid thermal conductivity measurements on dry and water-saturated samples have a considerable potential as a method to determine porosity in low-porosity crystalline rocks.