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Thermal Cone Penetration Test (T-CPT)
Published in Michael A. Hicks, Federico Pisanò, Joek Peuchen, Cone Penetration Testing 2018, 2018
P.J. Vardon, D. Baltoukas, J. Peuchen
Figure 11 presents example results of laboratory tests undertaken to investigate the sand density aspect. The thermal conductivity tests were performed using a KD2 Pro Thermal Properties Analyzer (Decagon Devices, Inc.) with a TR-1 thermal needle probe (100 mm length, 2.4 mm diameter), according to ASTM (2014). The samples had dry densities from ∼1.3 to ∼1.6 Mg/m3, so representing about a ± 10% volumetric strain from the mean. The initially moist samples were flooded with water and subjected to increasing densification by means of a vibrating table. The thermal conductivities for each sample have an average range of 0.24 W/mK and therefore for a 2% volumetric strain the approximate difference would be approximately 0.02 W/mK, which is within the measurement error.
Graphene-Based Hybrid Nanofluids and Its Application in Heat Exchangers
Published in K.R.V. Subramanian, Tubati Nageswara Rao, Avinash Balakrishnan, Nanofluids and Their Engineering Applications, 2019
Hooman Yarmand, Nurin Wahidah Binti Mohd Zulkifli, Mahidzal Dahari, S.N. Kazi
The most important property of nanofluid which must be measured is thermal conductivity. Thermal conductivities of nanofluids were measured by the KD-2 pro device (Decagon, United States), where KS-1 probe sensors were used having 6 cm and 1.3 mm length and diameter, respectively. The accuracy of the measured thermal conductivity is 5%. To ensure the equilibrium of nanofluids, an average of 16 measurements were recorded during 4 hours for each temperature and weight concentration. Calibration of instrument with DI water was performed before starting of the measurements of nanofluids. Thermal conductivity of DI water at 30°C was measured and a value of 0.61 W/mK found, which is in agreement with the previous investigations. Viscosity is also other important property of fluid flow. Pressure drop, pumping power, and heat transfer capability of fluid is directly dependent on the viscosity. Furthermore, the dynamic viscosity of nanofluid is investigated at various shear rates to find the rheological behavior of suspension, whether the suspension has Newtonian or non-Newtonian behavior. The viscosity of distilled water and different weight fractions of nanofluids were measured by rheometer Physica, MCR, Anton Paar, Austria. The rotational rheometer consists of a moving cylindrical plate and a stationary cylindrical surface which are parallel with a small gap. Viscosity of distilled water and nanofluid samples at various concentrations and temperatures in the range of 20°C–40°C at a shear rate of 500/s had been investigated. The measured viscosity of distilled water at 20°C is 1.10 (mPa sec).
Straightedge and Compass Constructions
Published in Stephen Hester, David Francis, Eric Livingston, Ethnographies of Reason, 2016
Stephen Hester, David Francis, Eric Livingston
A justification that the transcendentalized, idealized version of this procedure produces an inscribed regular pentagon is more complex. It involves the construction of an inscribed, regular decagon (ten-sided polygon).2
Unveiling students’ explorations of tessellations with Scratch through mathematical aesthetics
Published in International Journal of Mathematical Education in Science and Technology, 2022
Kenan Gökdağ, Meriç Özgeldi, İlker Yakın
In the first activity, students were asked to create regular tessellations with triangle, square, pentagon, hexagon, heptagon, octagon, nonagon, and decagon by using Scratch. All students created tessellations and realized that triangles, squares, and regular hexagons are the only regular polygons that will tessellate. The arrangement of Scratch code blocks showed their explorations on looking for appealing tessellation structure. In this activity, students first discovered the rule of calculating one external angle in a regular polygon (i.e. 360/n). Figure 2 shows the code blocks students used to create regular tessellations.
Diamond Nanofluids: Microstructural Analysis and Heat Transfer Study
Published in Heat Transfer Engineering, 2021
Farzin Mashali, Ethan M. Languri, Jim Davidson, David Kerns
The diamond nanofluids were prepared in concentrations of 0.01, 0.5, and 0.1 wt.%. The thermal conductivity of nanofluids has been measured using a KD2 device and probe (Decagon Devices Inc., USA) in a temperature range of 300–335 K. The KS-1 needle sensor with a length of 60 mm and a diameter of 1.3 mm with a thermal conductivity range of 0.02–2.00 W/m·K (± %5) was used for thermal conductivity measurements. The thermal conductivity measurement apparatus was placed on a vibration-free table. Further details of the thermal conductivity measurements can be found in another study of the same authors [31]. The thermal conductivity values of the diamond nanofluid samples are shown in Figure 3a. The improvement of thermal conductivity is not abnormal at the room temperature as reported in [32], but the heat transfer enhancement is increasing as temperature increases. The measured thermal conductivity values are compared with the one from the Maxwell model [33] which is described as follows: where kND and kDI stand for thermal conductivity of nanodiamond and deionized water, respectively. The volume fraction can be calculated from the weight fraction concentration according to Eq. (2) where ρ, W, and are density, weight, and volumetric concentration, respectively; ND and DI are subscripts for nanodiamond and deionized water, respectively. The correlation is valid for all the temperatures that no phase change occurs. The thermo-physical properties of diamond nanofluid at different concentrations are provided in Table 2. Density and specific heat are calculated while dynamic viscosity and thermal conductivity have been measured as described previously [34].
Sample volume of a capacitance moisture sensor in function of its geometry
Published in European Journal of Environmental and Civil Engineering, 2020
Xavier Chavanne, Jean-Pierre Frangi
Among studies dedicated to derive theoretically and/or experimentally the extent and localisation of the volume sampled by the sensor, we can mention the laboratory tests carried out by Baker and Lascano (1989) using a two-rod design. Their setup consisted in a row of water-filled tubes parallel to the probe axis and placed successively at different points in the sensor transverse plane to draw profiles of sensor sensitivity. Probes present a main axis, which coincides to electrode axis and usually to the largest dimension, and to which the electric field direction is mostly perpendicular. Variation of field amplitude is also much lower along the axis than in the transverse direction. As a result, the sample volume is approximately proportional to probe length. Studies thus largely focused on the section of the sample volume in the transverse plane or sample area. Baker and Lascano (1989)’s setup was criticised by Knight (1991) as unable to derive the sample volume. By using a row of tubes they incorrectly assumed that the sample area depends separately on the two coordinates of the transverse plane. Knight (1992) laid a theoretical basis to obtain the sample volume of a sensor. From the expression of the electrostatic energy, he introduced a spatial weighting function to measure the local sensor sensitivity. Using analytical expressions obtained by some simplifications, he attempted to determine the best dimensions of a two-rod probe. However, his sample volume remained ill-defined and his conclusion was elusive suggesting without clear justification a distance between rods lower than 10 times their diameter. As a matter of fact most sensors using a multi-rod design present a geometry close to this ratio (such as TDRs, or GS3 by Decagon Devices Inc., USA). Interestingly, Knight (1992) demonstrated that small disturbances from a uniform permittivity have only a second-order effect on the electrostatic energy.