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This study investigates the movements of particles in an accelerated toroidal flow channel filled with water, with specific applications for a particle imaging velocimetry gyroscope (PIVG). We used computational fluid dynamics (CFD) to simulate particle behavior under different angular accelerations. These angular accelerations were 4 rad/s2, 6 rad/s2, and 8 rad/s2 for particles densities of 1100 kg/m3, 1050 kg/m3, and 980 kg/m3. An examination was performed on the particles' concentration distribution, velocity profiles, and displacement patterns with respect to the toroidal geometry, which had a volume fraction of 1.5% and was sized at 50 microns. Our results show that particle density significantly affects behavior and displacement within the toroidal flow, with heavier particles (1100 kg/m3) settling more quickly and concentrating near the lower z values over time, while lighter particles (980 kg/m3) maintain a more uniform distribution. This understanding is crucial for optimizing PIVG accuracy and reliability. [ABSTRACT FROM AUTHOR]

The hypothesis of the present research is the existence of distinct spatial-temporal characteristics of non-oxidized liquid metal (LM) droplets impacting a solid surface. To provide a quantitative claim to this hypothesis, we created a test matrix based on the well-known impingement regime map bounded by two dimensionless quantities—Weber number (We) and Ohnesorge number (Oh). The range of these quantities is from 10−2 to 102 (We) and 10−3 to 101 (Oh), leading to Reynolds number (Re) (≡We1/2/Oh) to vary from 10−2 to 104. The class of LMs opted for are post-transition metals—eutectic gallium alloys—due to their several desired practical features, such as low melting point, non-toxicity, and low vapor pressure. The research is conducted using numerical experiments performed using C++ OpenFOAM libraries. To ensure the reliability of the code, we tested our work with numerous impingement behaviors of fluids available in the literature. A plethora of droplet behaviors are reported, such as deposition, rebound, bubble entrapment, and splash. Several features of droplet impingement were critically examined, such as temporal spreading factor, maximum spreading factor, and contact time of droplets on the surfaces. Moreover, the conventional scaling laws regarding the impingement behavior of droplets were tested, with new ones proposed where deemed necessary. Furthermore, a distinct route for the entrapment of droplet is observed, caused by the bulging of LM droplet during the recoiling stage. Emphasis is made to form delineations for these impingement characteristics using dimensionless groups (i.e., We, Oh, and Re). [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) nanocomposites with a polystyrene thermoplastic matrix were injection molded and the high shear stress exerted during the injection process partially enabled the alignment of the CNTs in the flow direction. Nanocomposites with different CNT loadings and degrees of alignment were produced, and their thermal conductivities were measured based on ASTM D5470. The results were compared with compression molded samples featuring random alignments of CNTs. The results showed that the injection molded samples possessed anisotropic thermal conductivities, due to the partial alignment of the CNTs in the flow direction. The effective medium approach was used to analytically estimate the thermal conductivity of the molded samples. Good agreement was observed between the experimental and analytically simulated results in lower CNT concentrations (less than 5 wt% of CNT). Using transmission electron microscopy pictures taken of the nanocomposites, the alignment of CNTs in the thermoplastic matrix were modeled; and their thermal conductivities were simulated using the finite element method. Good agreement was observed between the experiments and simulated results. POLYM. ENG. SCI., 55:753-762, 2015. © 2014 Society of Plastics Engineers, INTRODUCTION Thermally and electrically conductive polymers are widely used in the electronics, aerospace, and automotive industries to prevent static charge storage and dissipate heat. Traditionally, the fabrication of these composites [...]

The effect of a metallic porous matrix, inserted in a pipe, which is subjected to a constant and uniform heat flux, on the rate of heat transfer is investigated. In addition, the effects of porosity and thickness of the porous matrix on the heat transfer rate and pressure drop are investigated.

The paper presents a technical and economic analysis for two energy systems (conventional and renewable) with grid connection. The investigation was carried out using an experimental measurement for the desired load and weather data (solar irradiance and ambient temperature), were 5.1 kWh the daily energy consumption as measured and 4.6 kWh/m2/day the annual average of the solar irradiance. The simulation process was done by using MATLAB and HOMER software at a 1 min time step resolution. The economic optimization objective presented for two energy system scenarios (i) photovoltaic/grid and (ii) diesel/grid, takes into account the economic aspects and component prices based on the Iraqi market and regulations. The diesel generator, very popular in rural areas, is designed to work during the same period as the photovoltaic system (only during day hours). The yearly operating hours were recorded at 4380 h/year, and energy generation was approx. 2349 kWh/year while fuel consumption was 1826 L/year. The results showed that the photovoltaic system in scenario (i) can generate about 7895 kWh, and for the diesel generator in scenario (ii), it can generate approximately 2346 kWh. Furthermore, for scenario (i) the levelized net present cost is $1079 and the cost of energy is about $0.035/kWh, while for scenario (ii) the levelized net present cost is $12,287 and the cost of energy is $0.598/kWh. The use of solar energy is highly recommended compared to diesel generators due to the lowest cost and delivery of energy to the grid. Furthermore, it can capture carbon dioxide by about 5295 kg/year. [ABSTRACT FROM AUTHOR]