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This study presents an investigation of a heat pipe with a mesh wick, utilizing machine learning (ML) techniques. The model including radial basis function interpolation (RBF), Kriging model (KRG), and the k-nearest neighborhood model (K-NN) were studied and compared. A set of training and validating populations were classified using a k-means clustering technique. The design variable included the geometric shape of heat pipe such as its diameter, the properties and percentage used of working fluid, and the temperature at the evaporator. The prediction case study included the heat transfer rate (q), and total difference temperature between evaporator and condenser section (ΔT). The prediction results found that the ΔT gave the most accurate indicator while the q is passable to applied. The Kriging model proved to be the most accurate, achieving an RMSE of 0.9896 and R2 of 0.9149 for heat transfer rate prediction, and an RMSE of 0.1902 and R2 of 0.9398 for total temperature difference prediction with 90 % training data. The second-best accuracy was achieved by the RBF model, with the linear, thin plate, and cubic spline kernels performing reasonably well.

This study focuses on the numerical validation of a two-dimensional model of a heat pipe's temperature profile under transient conditions. The model was constructed from copper, and the finite difference method was employed as the numerical solver. The study recorded the temperature distribution at the pipe wall in the evaporator, adiabatic and condenser sections, with a focus on the initial temperatures of the evaporator section. The temperatures at the pipe wall were compared with the numerical computation solutions. The results showed an agreement between the experimental and numerical temperature profiles with percentage error between 4.463 and 5.900 %.

This research aims to study the heat transfer with a numerical model and experimental evaluation of a helical oscillating heat pipe (HOHP). Firstly, we created a numeric model of the HOHP to predict the time required to reach the steady state temperature and the heat transfer of the HOHP under transient conditions. Secondly, we measured the temperature at the pipe wall and evaluated the heat transfer rate from experiments and compared them with the numeric model. The results showed that the transient temperature and the heat transfer profiles of the HOHP from the numerical model were similar with the results measured from the experimental data. The results from numeric model predicted temperature profiles for attaining a steady state temperature were in close agreement, when compared to the numerical simulation of Boothaisong et al. (2015).

In this study, the effect of firing temperatures on phase formation, microstructure dielectric and magnetic properties of Ni0.6Zn0.4Fe2O4 (NZFO) ceramics were investigated. The NZFO powder were synthesized by the solid-state combustion technique using glycine as a fuel to reduce the reaction temperature. All samples were calcined in the range of 900 °C–1100 °C for 2 h and sintered in the range of 1175 °C–1275 °C for 2 h. A pure ferrite phase was found in the powders calcined above 1000 °C and the average particle size of NZFO powders was increased from 0.39 µm to 0.59 µm when the calcination temperature was increased. The x-ray diffraction (XRD) analysis results confirmed the formation of pure spinel structure with cubic phase in all the ceramic samples. The average grain size (5.54–2.80 µm) was slightly decreased, and the dielectric constant (239–13) tended to decrease with increasing sintering temperature. As the sintering temperature increased to 1250 °C, it was found that the lattice parameters (8.366–8.387 Å), the density (5.29–5.35 g/cm3), and saturation magnetization (81.51–93.92 emu/g) tended to increase after that decrease. [ABSTRACT FROM AUTHOR]

(Bi0.38Na0.30Sr0.28)0.98La0.02Ti1-xZrxO3 (abbreviated as BNSLT1-xZrx, with x = 0 − 0.05) lead free ceramics were fabricated using the solid-state combustion method. The phase structure, microstructure and electrical properties of the ceramics were investigated. The coexistence of the rhombohedral (R) and tetragonal (T) phases was found in all samples. Rietveld refinement confirmed that as x increased from 0 to 0.05, the rhombohedral phase increased from 41 to 60%. A nearly equal R:T phase ratio of 49:51 was obtained for x = 0.01. All ceramics displayed polygonal grain shapes with anisotropic grain growth. The average grain size of the ceramics was in the range of 0.46–0.79 µm. The optimal Zr4+ content resulted in increased grain growth and reduced pores, leading to improved electrical properties. The highest density (5.52 g/cm3), maximum dielectric constant (εm=2156), maximum polarization (Pmax=15.36 µC/cm2) and high energy storage properties (Wtotal=0.49 J/cm3, Wrec=0.45 J/cm3, Wloss=0.05 J/cm3 and η = 90.54% at 60 kV/cm) were obtained from x = 0.01 caused by a morphotropic phase boundary (MPB) and good morphology. [ABSTRACT FROM AUTHOR]

This study focuses on the numerical validation of a two-dimensional model of a heat pipe's temperature profile under transient conditions. The model was constructed from copper, and the finite difference method was employed as the numerical solver. The study recorded the temperature distribution at the pipe wall in the evaporator, adiabatic and condenser sections, with a focus on the initial temperatures of the evaporator section. The temperatures at the pipe wall were compared with the numerical computation solutions. The results showed an agreement between the experimental and numerical temperature profiles with percentage error between 4.463 and 5.900 %. [ABSTRACT FROM AUTHOR]

In this article, an optimization technique using the Taguchi method with multiple performance characteristics for the percent zinc coating balances edge joints of galvanized steel sheets for metal inert gas pulse brazing process was proposed. The orthogonal array, multi-response signal-to-noise ratio, and analysis of variance were employed to study the performance characteristics. Five metal inert gas pulse brazing process parameters, namely, wire feed speed, arc voltages, travel speed, peak currents, and pulse frequency, were optimized with considerations of multiple performance characteristics including percent zinc coating balances edge joints. Experimental results were provided to confirm the effectiveness of this approach. The optimum metal inert gas pulse brazing technique conditions were wire feed speed of 3.25 m/min, arc voltages of 18 V, travel speed of 0.8 m/min, peak currents of 425 A, and pulse frequency of 35 Hz. Confirmation tests of the optimal levels with the initial cutting parameters are carried out in order to illustrate the effectiveness of this method in metal inert gas pulse brazing technique for galvanized steel sheets.

The objective of this work was to optimize the percent zinc coating balances edge joints of galvanized steel sheets using the metal inert gas pulse brazing process. The Taguchi method and grey relational analysis were used to determine the relationship between the metal inert gas pulse brazing process parameters and percent zinc coating balances edge joints. The metal inert gas pulse brazing process parameters used in this study included wire feed speeds, arc voltages, travel speed, peak currents, and pulse frequency. The characteristics of metal inert gas pulse brazing process that were considered to find response were percent zinc coating balances edge joints on the upper edge joint (PZBEJ1), the lower edge joint (PZBEJ2), and the back sides of the edge joint (PZBEJ3). Analysis of variance was performed to determine the impact of an individual process parameter on the quality parameters. The results showed that the optimal parameters in which grey relational grade increases at the highest level were wire feed speeds at 3.25 m/min, arc voltages at 16 V, travel speeds at 0.9 m/min, peak currents at 425 A, and pulse frequency at 35 Hz. These parameters gave a 74.90% higher response value than those of the initial parameters of metal inert gas pulse brazing process.

The aim of this study was to perform life testing and determine the effect of working fluid on the corrosion of a heat pipe with a sintered wick. The heat pipe was made from a copper tube. The inner heat pipe was filled with 99.97% pure copper powder as a dendritic for the sintering process. The heat pipe had an outer diameter of 6 mm with a length of 200 mm, and distilled water and ethanol were the working fluids. The operating temperature at the evaporator was 125°C. The analysis consisted of using a scanning electron microscope, energy dispersive X-ray spectrometry and atomic absorption spectroscopy. The results of the scanning electron microscope and energy dispersive X-ray spectrometry analysis showed that the corrosion of the heat pipe was uniform. The result of the atomic absorption spectroscopy indicated that the concentration of the copper in the ethanol as the working fluid was greater than in the distilled water as the working fluid, and the highest concentration of copper particles in the ethanol was 22.7499 ppm or 0.0409 mg after testing for 3000 h. The concentration of copper was higher when the length of the life test increased due to corrosion of the heat pipe.

A three-dimensional model was developed to simulate the heat transfer rate on a heat pipe in a transient condition. This article presents the details of a calculation domain consisting of a wall, a wick, and a vapor core. The governing equation based on the shape of the pipe was numerically simulated using the finite element method. The developed three-dimensional model attempted to predict the transient temperature, the velocity, and the heat transfer rate profiles at any domain. The values obtained from the model calculation were then compared with the actual results from the experiments. The experiment showed that the time required to attain a steady state (where transient temperature is constant) was reasonably consistent with the model. The working fluid r134a (tetrafluoroethane) was the quickest to reach the steady state and transferred the greatest amount of heat.

This research aims to study the effect of evaporator temperature, pitch distance, and working fluid on the internal flow pattern and the heat transfer characteristics of the helical oscillating heat pipe. A Pyrex tube with an inner diameter of 2.4 mm was used to study the flow pattern in the evaporator section. The pitch distance varied at 1, 1.5, and 2 cm. Water and R-123 were used as working fluid with a filling ratio of 80% by total volume. In the evaporator section, the water temperature varied at 60, 75, and 90°C to supply heat to the heat pipe. In the condenser section, air with a temperature of 25°C was used as heat sink. From the results, it was found that 4 internal flow patterns, bubble flow, slug flow, annular flow, and stratified wavy flow, were observed in the evaporator section for both working fluids. The heat transfer rate decreased when the pitch distance was increased from 1 to 2 cm. The maximum heat flux was 2,132.6 and 1,773.4 W/m 2 for the working fluid of R-123 and water, respectively. Both occurred at a pitch distance of 1 cm and an evaporator temperature of 90°C.

Sheet metal extrusion is a metal forming process in which the movement of a punch penetrates a sheet metal surface and it flows through a die orifice; the extruded parts can be deflected to have an extrusion cavity and protrusion on the opposite side. Therefore, this process results in a narrow region of highly localized plastic deformation due to the formation and microstructure effect on the work piece. This research investigated the characteristics of the material-flow behavior during the formation and its effect on the microstructure of the extruded sheet metal using the finite element method (FEM). The actual parts and FEM simulation model were developed using a blank material made from AISI-1045 steel with a thickness of 5 mm; the material’s behavior was determined subject to the punch penetration depths of 20%, 40%, 60%, and 80% of the sheet thickness. The results indicated the formation and microstructure effects on the sheet metal extrusion parts and defects. Namely, when increasing penetration, narrowing the die orifice the material flows through, the material was formed by extruding, and defects were visibility, and the microstructure of the material’s grains’ size was flat and very fine. Extrusion defects were not found in the control material flow. The region of highly localized plastic deformation affected the material gain and mechanical properties. The FEM simulation results agreed with the experimental results. Moreover, FEM could be investigated as a tool to decrease the cost and time in trial and error procedures.

This research presents a case study of the rating heat transfer of a loop thermosyphon with a vapour chamber (LTVC). The dimensions of the evaporator chamber were 200 × 200 × 55, 200 × 200 × 65 and 200 × 200 × 75 mm ( W × L × H ). The adiabatic and condenser section had an 8-loops thermosyphon. The length of the adiabatic and condenser section in each loop was 824 and 800 mm, respectively. The air velocity was 0.5, 1.0, and 1.5 m/s with the heat input being 600, 900, and 1,200 W. The three working fluids were: water, ethanol, and R-11 with filling ratios of 20, 40, and 60% with respect to the chamber volume. The experimental data showed that the LTVC yielded the value of the relative thermal efficiency of about 1 at R-11, a filling ratio of 60%, a velocity of 0.5 m/s, and an aspect ratio of 2.5 in the study conditions. It was further found that the larger vapour chamber was superior in the rating of the heat transfer over other vapour chambers in all experimental conditions in this study.

Lead-free [(Bi0.5Na0.5)0.94Ba0.06]1-xLaxTiO3 (BNBT-xLa) ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol.% were synthesized by the solid-state combustion technique with calcination and sintering temperatures of 750 °C and 1150 °C, respectively, for 2 h. The phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBT-xLa ceramics were investigated. The XRD patterns of the powders showed a pure perovskite phase for all samples. The average particle size increased from 298 to 379 nm with increasing x. All ceramics showed coexisting rhombohedral and tetragonal phases. When x rose, the content of the tetragonal phase increased, as validated by the Rietveld refinement method. The average grain size decreased from 1.43 to 0.81 µm when x increased from 0 to 0.05 and then started to increase. The Curie temperature (Td) of the samples shifted to lower temperatures with rising x, owing to an increased tetragonal phase. The maximum dielectric constant (εm), remanent polarization (Pr) and coercive field (Ec) decreased with increasing x. The BNBT-0.05La ceramic exhibited the smallest grain size, and lowest Pr = 0.8 µC/cm2 and Ec = 2.9 kV/cm, with the highest energy storage efficiency (η ∼ 78.31%) and a large effective energy storage density (W ∼ 0.83 J/cm3) measured in an electric field of 80 kV/cm. [ABSTRACT FROM AUTHOR]

The (1-x)Mg0.7Zn0.3Fe2O4 – (x)Ba0.7Sr0.3TiO3 composites with x = 0.40, 0.50 and 0.60 were prepared by solid state reaction under two step sintering. Two step sintering conditions were determined by the first step (T1) at 1350 °C for holding time of 60 min and cooled down to the second sintering temperature (T2) with different temperatures between 900 and 1100 °C for holding time of 5 h. The sample with high percentage of shrinkage and dense ceramic was obtained from 0.4Mg0.7Zn0.3Fe2O4-0.6Ba0.7Sr0.3TiO3 with sintering of T2 at 1100 °C. XRD pattern showed combination of ferrite phase (Mg0.7Zn0.3Fe2O4) and ferroelectric phase (Ba0.7Sr0.3TiO3) and secondary phase of ZnO. Rietveld analysis confirmed main phases of Mg0.7Zn0.3Fe2O4 and Ba0.7Sr0.3TiO3, including MgFe2O4 and ZnO as secondary phase. It was found that the unit cell volume of Ba0.7Sr0.3TiO3 was smaller than Mg0.7Zn0.3Fe2O4 unit cell volume. Therefore, the short distance between ions of Ba0.7Sr0.3TiO3 phase produced the dense composites with increasing ferroelectric phase contents. The average grain size of ceramic was in the range of 0.74–1.07 µm with grain square shape in Mg0.7Zn0.3Fe2O4 phase and the average grain size of 0.59–0.70 µm with round oval shape in Ba0.7Sr0.3TiO3 phase. The dielectric constant was between 0.8 × 103 and 5.4 × 103 in the temperature range of 275 °C − 360 °C. The highest dielectric constant was obtained from 0.6Mg0.7Zn0.3Fe2O4−0.4Ba0.7Sr0.3TiO3 with T1 at 1350 °C with holding time for 60 min and T2 at 900 °C with holding time for 5 h. The hysteresis measurement was carried out to determine saturation magnetization, remanent magnetization and coercivity of the composites. The results revealed that higher concentration of ferrite led to optimal magnetic properties. [ABSTRACT FROM AUTHOR]