Inert Gas Axial Flow Analysis on Thermal System with Natural Convection Condition

The Fukushima nuclear accident in 2011 became the basis for consideration of the use of gas as a coolant in nuclear reactors. This is because the convection rate of gas flow in the cooling channel can occur naturally due to differences in density and does not require the help of a pumps for the circulation of the coolant. This study aims to analyze how the flow pattern of an inert gas on a vertical-axial reference by natural convection in a thermal system. The focus of this research is to study the flow parameters of the coolant with a gas phase. This research is an experimental study. The analysis was carried out using a descriptive approach and computer simulation-assisted numerical analysis methods. The results showed that the distribution and variation of heat was radially dominant in the middle so that the coolant channel wall received less heat load. The magnitude of the pressure drop along the vertical-axial channel shows a homogeneous pattern and decreases radially from center to edge. These results indicate the use of inert gas as a coolant can be considered as an alternative coolant in heat systems that do not depend on pumps in operating conditions

Phase field simulation of liquid filling on grooved surfaces for complete, partial, and pseudo-partial wetting cases

We develop and harness a phase field simulation method to study liquid filling on grooved surfaces. We consider both short-range and long-range liquid–solid interactions, with the latter including purely attractive and repulsive interactions as well as those with short-range attraction and long-range repulsion. This allows us to capture complete, partial, and pseudo-partial wetting states, demonstrating complex disjoining pressure profiles over the full range of possible contact angles as previously proposed in the literature. Applying the simulation method to study liquid filling on grooved surfaces, we compare the filling transition for the three different classes of wetting states as we vary the pressure difference between the liquid and gas phases. The filling and emptying transitions are reversible for the complete wetting case, while significant hysteresis is observed for the partial and pseudo-partial cases. In agreement with previous studies, we also show that the critical pressure for the filling transition follows the Kelvin equation for the complete and partial wetting scenarios. Finally, we find the filling transition can display a number of distinct morphological pathways for the pseudo-partial wetting cases, as we demonstrate here for varying groove dimensions

PENGEMBANGAN PROTOTIPE SEL SURYA DSSC (DYE SENSITIZED SOLAR CELL) LAPISAN TiO2/GRAFIT MENGGUNAKAN CAMPURAN PCBM:P3HT

Dalam penelitian ini telah berhasil dibuat prototipe sel surya organic tipe dye-sensitized solar cells (DSSC) lapisan TiO2 /grafit dengan menambahkan lapisan aktif polimer campuran phenyl-C61-butyric acid methyl ester (PCBM) dan regioregular poly(3-hexylthiophene) (P3HT). Dye dari ekstrak buah naga digunakan sebagai photosensitizer untuk menghasilkan exciton. Campuran PCBM:P3HT divariasikan dengan perbandingan 1:1, 1:2 dan 2:1 untuk melihat pengaruh dari masing-masing polimer. Hasil karakterisasi absorbansi menggunakan UV-Vis spektrometer pada lapisan TiO2/Grafit yang ditambahkan dengan lapisan PCBM:P3HT menunjukkan peningkatan nilai serapan pada panjang gelombang 300 – 650 nm. Namun, peningkatan ini tidak sejalan dengan peningkatan nilai efisiensi sel surya. Hasil pengukuran I-V karakteristik dibawah penyinaran sinar matahari langsung menunjukkan penurunan effisiensi sel surya sebesar 20.4% pada penambahan campuran PCBM:P3HT (1:1), 43.6% untuk PCBM:P3HT (1:2) dan 96.5% untuk PCBM:P3HT (2:1). Penurunan ini lebih disebabkan karena menurunnya nilai tegangan sirkuit terbuka, V­oc. Selain itu, nilai efisiensi sel surya yang rendah (yakni < 1%) disebabkan karena nilai rapat arus yang sangat kecil yakni pada orde beberapa mikro Ampere. Kami menduga kecilnya nilai rapat arus ini disebabkan oleh nilai resistansi internal yang cukup besar pada sel surya serta berubahnya peran lapisan PCBM:P3HT yang seharusnya berfungsi untuk meningkatkan penghantaran exciton menjadi pusat rekombinasi. Hal ini mungkin disebabkan karena tebalnya lapisan PCBM:P3HT yang dibuat menggunakan metode drop-casting seperti yang ditunjukkan dari hasil karakterisasi SEM. Kata Kunci: Sel surya DSSC, dye-sensitized, poly(3-hexylthiophene), [6,6]-phenyl-C61-butyric acid methyl ester, lapisan TiO2/Grafit

Predicting Hemiwicking Dynamics on Textured Substrates

The ability to predict liquid transport rates on textured surfaces is key to the design and optimization of devices and processes such as oil recovery, coatings, reaction-separation, high-throughput screening, and thermal management. In this work we develop a fully analytical model to predict the propagation coefficients for liquids hemiwicking through micropillar arrays. This is carried out by balancing the capillary driving force and a viscous resistive force and solving the Navier–Stokes equation for representative channels. The model is validated against a large data set of experimental hemiwicking coefficients harvested from the literature and measured in-house using high-speed imaging. The theoretical predictions show excellent agreement with the measured values and improved accuracy compared to previously proposed models. Furthermore, using lattice Boltzmann (LB) simulations, we demonstrate that the present model is applicable over a broad range of geometries. The scaling of velocity with texture geometry, implicit in our model, is compared against experimental data, where good agreement is observed for most practical systems. The analytical expression presented here offers a tool for developing design guidelines for surface chemistry and microstructure selection for liquid propagation on textured surfaces