Pengaruh Jumlah Sudu 8, 12, 16 dan 20 terhadap Performa Hidro-Turbin Cross-Flow dengan sudut 15° Menggunakan Metode Computational Fluids Dynamics

<p>Energi listrik merupakan kebutuhan primer dalam kehidupan sehari-hari. Perkembangan teknologi mengakibatkan meningkatnya kebutuhan energi listrik setiap tahunnya. Energi baru terbarukan memasok kebutuhan energi listrik nasional sebesar 14%. Di sisi lain, pemerintah mengharapkan komposisi energi baru terbarukan sebesar 23% hingga 31% pada tahun 2050. Hal ini menunjukan bahwa energi baru terbarukan masih memiliki gap yang cukup tinggi. Penelitian ini merupakan salah satu upaya dalam pengembangan energi baru terbarukan, terutama pada pembangkit listrik mikro-pico hidro. Penelitian ini dilakukan menggunakan metode <em>Computational Fluid Dynamics</em> menggunakan Aplikasi Ansys dengan CFX <em>Solver</em>. Penelitian dilakukan untuk mengetahui pengaruh jumlah sudu pada hidro-turbin <em>cross-flow</em> terhadap performa <em>Coefficient of Power</em>. Peneltian dilakukan pada rotor dengan dimensi diameter 80 mm, panjang 130 mm dan sudut sudu 15°. Variasi jumlah sudu dilakukan pada jumlah sudu 8, 12, 16, dan 20. Simulasi dilakukan pada <em>steady state,</em> dan menggunakan tipe turbulen <em>Shear Stress Transport</em>. Turbin <em>cross-flow</em> beroperasi pada kecepatan air 3m/s dengan kecepatan sudut pada interval 50 sampai 350 RPM. Hasil menunjukan <em>Coefficient of Power Maximum</em> yang dihasilkan untuk sudu 8,12, 16 dan 20 adalah 10,8%; 14,1%; 16,8% dan 20,1%. Dari hasil tersebut menunjukan performa maksimal dihasilkan oleh hidro-turbin tipe <em>cross-flow</em> dengan jumlah sudu rotor 20.</p>

Numerical Investigation of Dropwise Condensation on Smooth Plates with Different Wettability

Condensers are used in various energy-intensive processing industries. Improving their efficiency plays a crucial role in the optimization of energy consumption. Dropwise Condensation is a highly attractive form of heat transfer. This project investigates the effects of different wettability characteristics in drop-wise condensation on smooth plates. It involves a Volume of Fluid (VOF) based Computational Fluids Dynamics (CFD) model to carry out the simulations in Open FOAM on smooth plates various wettability’s. Different parameters such as receding angle, advancing angle, and various radii of droplets have been used for investigation. A base case with droplets’ radius of 12.5μm, receding angle, and advancing angles of (34°, 90°) was used. Three sets of simulations were performed. In Set 1, the angles were (34°, 90°). The radius of the first droplet was kept constant at 12.5μm and the radius of the second droplet changes 1:4 progressively. In Set 2, the angles are changed to (154°, 162°), and the radius of the second droplet changes in the same manner above. In Set 3, the angles were kept at (107°, 117°). The radius changes as above. In some cases, the droplets merge and condense. In others, the momentum created by merging of the droplets creates repeated oscillation or even a lift-off, from the cooling plate.

On Finding the Right Sampling Line Height through a Parametric Study of Gas Dispersion in a NVB

The tracer gas method is one of the common ways to evaluate the air exchange rate in a naturally ventilated barn. One crucial condition for the accuracy of the method is that both considered gases (pollutant and tracer) are perfectly mixed at the points where the measurements are done. In the present study, by means of computational fluids dynamics (CFD), the mixing ratio NH3/CO2 is evaluated inside a barn in order to assess under which flow conditions the common height recommendation guidelines for sampling points (sampling line and sampling net) of the tracer gas method are most valuable. Our CFD model considered a barn with a rectangular layout and four animal-occupied zones modeled as a porous medium representing pressure drop and heat entry from lying and standing cows. We studied three inflow angles and six combinations of air inlet wind speed and temperatures gradients covering the three types of convection, i.e., natural, mixed, and forced. Our results showed that few cases corresponded to a nearly perfect gas mixing ratio at the currently common recommendation of at least a 3 m measurement height, while the best height in fact lied between 1.5 m and 2.5 m for most cases.

Analysis of the purge time values for pressurized enclosure using a parameterized CFD model

The use of computerized simulations offers definite advantages in understanding phenomena and analysing parameters that have influence during a complex process, more can provide on the basis of scenarios valuable information on the effects for physical processes analysed. Thus, in this paper, using mathematical models and numerical solutions based on physical principles and functions with assumed accuracy are analyse, using CFD (Computational fluids dynamics), the values of purge time for pressurized enclosure, resulting in the action of post-processing of construction for graphs and colour icons, in order to render images as representative possible both for the design phase of the equipment with protection type pressurization “p” and for their evaluation for certification. Determining the values of purging time by using computer simulations is particularly important for avoiding catastrophic events caused by explosions that can lead to human casualties, significant material losses or have significant environmental consequences.

Investigation on the Energy Exchange Characteristics of the Regenerative Flow Pump in an Automobile Fuel System

The flow inside the regenerative flow pump (RFP) is quite complex. This study investigated four pump models with various geometrical dimensions to explore the energy exchange characteristics. A computational fluids dynamics (CFD) simulation and the experiment were carried out. The results illustrate that the pressure growth mode in the impeller is consistent with the channels, which confirms the circulation flow existing in the pump. Furthermore, it is found that the circulation flow that features with longitudinal vortexes can be evaluated quantitatively by combining the analyses of the dimensionless axial distance, circulation number and entropy production. A smaller axial distance indicates that more flow is involved in the circulation and the intensity of the longitudinal vortex is enhanced; a large circulation number accompanied by a small dissipation loss could result in a satisfactory exchange flow. Therefore, the largest circulation number, least amount of dissipation, and shortest distance lead to the highest head and efficiency in the model with V-shaped blades and an increased impeller height. This work establishes a deeper understanding of the energy exchange mechanism and could serve as a reference for the geometrical design and performance reinforcement of RFP.

Parametric Study on a Performance of a Small Counter-Rotating Wind Turbine

A small Counter-Rotating Wind Turbine (CRWT) has been proposed and its performance has been investigated numerically. Results of a parametric study have been presented in this paper. As parameters, the axial distance between rotors and a tip speed ratio of each rotor have been selected. Performance parameters have been compared with reference to a Single Rotor Wind Turbine (SRWT). Simulations were carried out with Computational Fluids Dynamics (CFD) solver and a Large Eddy Scale approach to model turbulences. An Actuator Line Model has been chosen to represent rotors in the computational domain. Summing up the results of simulation tests, it can be stated that when constructing a CRWT turbine, rotors should be placed at a distance of at least 0.5 D (where D is rotor outer diameter) or more. One can then expect a noticeable power increase compared to a single rotor turbine. Placing the second rotor closer than 0.5 D guarantees a significant increase in power, but in such configurations, dynamic interactions between the rotors are visible, resulting in fluctuations in torque and power. Dynamic interactions between rotor blades above 0.5 D are invisible.

Bioink Temperature Influence on Shear Stress, Pressure and Velocity Using Computational Simulation

Bioinks are usually cell-laden hydrogels widely studied in bioprinting performing experimental tests to tune their rheological properties, thus increasing research time and development costs. Computational Fluids Dynamics (CFD) is a powerful tool that can minimize iterations and costs simulating the material behavior using parametric changes in rheological properties under testing. Additionally, most bioinks have specific functionalities and their properties might widely change with temperature. Therefore, commercial bioinks are an excellent way to standardize bioprinting process, but they are not analyzed in detail. Therefore, the objective of this work is to study how three temperatures of the Cellink Bioink influence shear stress pressure and velocity through computational simulation. A comparison of three conical nozzles (20, 22, and 25G) for each temperature has been performed. The results show that shear stress, pressure, and velocity vary in negligible ranges for all combinations. Although these ranges are small and define a good thermo-responsive bioink, they do not generate a filament on the air and make drops during extrusion. In conclusion, this bioink provides a very stable behavior with low shear stress, but other bioprinting parameters must be set up to get a stable filament width.

Effect of Open Boundary Conditions and Bottom Roughness on Tidal Modeling around the West Coast of Korea

The aim of this study was to investigate the effect of open boundary conditions and bottom roughness on the tidal elevations around the West Coast of Korea (WCK) using an open-source computational fluids dynamics tool, the TELEMAC model. To obtain a detailed tidal forcing at open boundaries, three well-known assimilated tidal models—the Finite Element Solution (FES2014), the Oregon State University TOPEX/Poseidon Global Inverse Solution Tidal Model (TPXO9.1) and the National Astronomical Observatory of Japan (NAO.99Jb)—have been applied to interpolate the offshore tidal boundary conditions. A number of numerical simulations have been performed for different offshore open boundary conditions, as well as for various uniform and non-uniform bottom roughness coefficients. The numerical results were calibrated against observations to determine the best fit roughness values for different sub-regions within WCK. In order to find out the dependence of the tidal elevation around the WCK on the variations of open boundary forcing, a sensitivity analysis of coastal tide elevation was carried out. Consequently, it showed that the tidal elevation around the WCK was strongly affected by local characteristics, rather than by the offshore open boundary conditions. Eventually, the numerical results can provide better quantitative and qualitative tidal information around the WCK than the data obtained from assimilated tidal models.

CFD simulation on centrifugal pump impeller with splitter blades

ABSTRACT The present paper aims to present the analysis and comparison of results of computational simulations using Computational Fluids Dynamics (CFD) in impellers of centrifugal pump. Three impellers were simulated: 1) original impeller, 2) original impeller with splitter blades at outlet; 3) original impeller with splitter blades at inlet. The splitters occupied 30% of the length of the main blades. They were simulated using the ANSYS-CFX software system in 1500 rpm rotational speed and at different flow rates. The turbulence model assumed was the Shear Stress Transport (SST). The results were used to build impeller blade head curves, besides the presentation of pressure distribution and streamline behaviour inside the impeller. It was verified that the insertion of the splitter blades reduced the impeller blade head, mainly the impeller with outlet splitter, whose reduction was more intense.