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Steady-State Conduction in Multiple Dimensions
Published in William S. Janna, Engineering Heat Transfer, 2018
The pin-fin problem, solved numerically is shown schematically in Figure 3.16, in which the fin is divided into four sections. Repeat the development for such a problem by dividing the region into three sections. Solve for θ in any convenient way, using mL = 2. Graph θ versus ξ for the three-section formulation, the four-section formulation, and the exact solution.Repeat Problem 39 for a five-section formulation. Graph θ versus ξ for the five-section formulation and compare to the exact solution. Let mL = 2.Figure P3.41 shows a cup of coffee with a spoon partly submerged. The coffee is at 90°C, which is the temperature of the spoon at the liquid surface. The spoon handle extends 80 mm above the coffee surface and can be approximated as a rod 7 mm in diameter. The ambient temperature is 22°C, and the convection coefficient is 3 W/(m2 ⋅ K). The spoon is made of stainless steel (assume Type 304). Graph the temperature versus length from the free surface. Use the exact solution and the four-section numerical formulation. Compare the results. A glass beaker contains some chemicals that undergo a heat-producing reaction. A glass rod is used to stir the mixture. When the rod is stationary, as shown in Figure P3.42, heat is conducted axially along the rod and transferred by convection to the surrounding air. A rod length of 6 in. extends above the liquid surface. The rod diameter is 1/4 in. At the liquid surface, the rod temperature is 200°F: (a) using the pin-fin equations for the case where the exposed tip is assumed insulated, graph the temperature distribution existing within the rod; (b) use the numerical formulation of this section to obtain the temperature distribution; and (c) compare the two models to determine how well the numerical results approximate the exact results. Use a convection coefficient of 1.1 BTU/(hr ⋅ ft2 ⋅ °R) and an ambient temperature of 68°F. A stainless steel stirring rod is used in Example 3.4. Repeat the calculations for an aluminum rod.Repeat Problem 39 for a six-section formulation. Compare the results to the exact solution.
Study on the stability of emulsion based on molecular dynamics
Published in Journal of Dispersion Science and Technology, 2021
Hongxin An, Guangsheng Cao, Yujie Bai, Daye Wang, Fansong Meng
Seal 30 ml sample oil and 70 ml deionized water and place it in a 60 °C constant temperature box to ensure that the crude oil and water are at the selected temperature during the emulsification process. Take out the sample oil and water that are stable at 60 °C, add the water to the emulsion bottle, add a certain amount of surfactant (mass concentration 0.5%), and stir the mixture thoroughly with a glass rod. Then put the lotion bottle under the mixer, adjust the position of the lotion bottle and the mixer head, make the head at a deeper position in the center of the mixture, and adjust the speed to 7500 rpm. Then the crude oil is gradually added to the stirring mixture to make it fully mixed to achieve a better emulsification effect. At this time, the outside of the emulsion bottle is heated with a water bath to ensure that the mixture is always at the selected temperature during the mixing process. After stirring continuously for 25 min, place the emulsion in a water bath for observation, and record the layering situation and the corresponding layering time.
Influence of nanoparticles on mechanical and nondestructive properties of high-performance concrete
Published in Journal of the Chinese Advanced Materials Society, 2018
Taher A. Tawfik, Magdy A. Abd EL-Aziz, S. Abd El-Aleem, A. Serag Faried
The hardness and nondestructive properties of HPC for control and modified, with different percentages of nanoparticles, specimens were discussed in the present research work. NS is prepared chemically using the precipitation method. Silica gel is refluxed with 6 N hydrochloric acid for 4 hours to get rid of iron then washed by deionized water many times to get rid of the acid. The obtained silica was grinded into powder form, then dissolved in 2 N sodium hydroxide by continuous stirring for 2 days on a magnetic stirrer. Concentrated H2SO4 was added to the alkaline silicate solution dropwise with continuous stirring using a glass rod for precipitation of silica. The pH was adjusted at 7.5–8.5. The precipitated silica was washed repeatedly with warm deionised water for 6 days till the filtrate becomes completely alkali free. Silica was then dried at 50 °C in an air oven for 2 days. The silica was obtained in nanoscale and collected through sieving with a mechanical sieve.[27] Nanowaste materials NSF, NFA and NC were prepared by mechanical grinding of SF, FA and C, respectively, that used as purchased.
Colorimetric determination of mercury vapor using smartphone camera-based imaging
Published in Instrumentation Science & Technology, 2018
Alan Rodelle M. Salcedo, Fortunato B. Sevilla
The sensing layer was prepared by mixing 0.5 g of CuI powder with a binder solution made by dissolving 0.05 g of polymer in 1.0 mL tetrahydrofuran or ultrapure water. The resulting emulsion was applied onto a chromatography paper (Whatman, 3MM CHR, 11 × 14 cm) through a roll-coating technique using a glass rod. This technique ensures an even distribution of the emulsion on the substrate. The reagent phase was then dried at 40°C in an oven for 30 min to produce the colorimetric sensing paper that contains the CuI/polymer composite. The colorimetric sensing paper was then cut into small pieces (10 × 10 mm2) and set on a glass slide for easier handling during the experiments.