|
CFD SIMULATION OF TRANSONIC FLOW IN HIGH-VOLTAGE CIRCUIT BREAKER
|
|
|
Xiangyang Ye, Mahesh Dhotre
|
|
A high-voltage circuit breaker is an indispensable piece of equipment in the electric transmission and distribution systems.
Transonic flow typically occurs inside breaking chamber during the current interruption, which determines the insulating characteristics
of gas. Therefore, accurate compressible flow simulations are required to improve the prediction of the breakdown
voltages in various test duties of high-voltage circuit breakers. In this work, investigation of the impact of the solvers on the
prediction capability of the breakdown voltages in capacitive switching is presented. For this purpose, a number of compressible
nozzle flow validation cases have been presented. The investigation is then further extended for a real high-voltage circuit breaker
geometry. The correlation between the flow prediction accuracy and the breakdown voltage prediction capability is identified....
More
|
|
|
VALORIZATION OF AGROINDUSTRIAL WASTES AS BIOSORBENT FOR THE REMOVAL OF TEXTILE DYES FROM AQUEOUS SOLUTIONS
|
|
|
Elsa Contreras, Luisa Sepulveda, Carolyn Palma
|
|
The goal is to determinate the technical feasibility of using agroindustrial wastes for adsorption of dyes. The pHpzc of Brewer’s spent
grains and Orange peel is 5.3 and 3.5, respectively. The equilibrium isotherms of Basic Blue 41, Reactiive Black 5, and Acid Black 1
were carried out without pHs control which ranging between 4 and 5.5. The equilibrium concentrations for both adsorbents were
fitted by the Freundlich and Langmuir models. The maximum adsorption capacity measured for Basic Blue 41, Reactive Black 5,
and Acid Black 1 was 32.4, 22.3, and 19.8 mg g-1 for Brewer’s spent grains; and 157, 62.6, and 45.5 for orange peel, respectively. The
kinetic of process was fitted by the model of pseudo-second order. The constant rate for orange peel decreased to extend the initial
concentration of dye increased, obtaining 4.08 * 10-3-0.6 * 10-3 (Basic Blue 41), 2.98 * 10-3-0.36 * 10-3 (Acid Black 1), and
3.40 * 10-3-0.46 * 10-3 gmg-1 min-1 (Reactive Black 5). The best removal efficiency was obtained in orange peel with values
started from 63% to 20%. Consequently, according the results obtained there are two positive effects, the reuse of agricultural
wastes and its use as low-cost adsorbent of the dyes....
More
|
|
|
NUMERICAL STUDIES ON HEAT RELEASE RATE IN ROOM FIRE ON LIQUID FUEL UNDER DIFFERENT VENTILATION FACTORS
|
|
|
N Cai, W K Chow
|
|
Heat release rate (HRR) of the design fire is the most important parameter in assessing building fire hazards. However, HRR in
room fire was only studied by computational fluid dynamics (CFD) in most of the projects determining fire safety provisions by
performance-based design. In contrast to ten years ago, officers in the Far East are now having better knowledge of CFD. Two
common questions are raised on CFD-predicted results on describing free boundaries; and on computing grid size. In this work,
predicting HRR by the CFD model was justified with experimental room pool fire data reported earlier. The software fire dynamics
simulator (FDS) version 5 was selected as the CFD simulation tool. Prescribed input heating rate based on the experimental results
was used with the liquid fuel model in FDS. Five different free boundary conditions were investigated to predict HRR. Grid
sensitivity study was carried out using one stretched mesh and multiple uniform meshes with different grid sizes. As it is difficult
to have the entire set of CFD predicted results agreed with experiments, macroscopic flow parameters on the mass flow rate through
door opening predicted by CFD were also justified by another four conditions with different ventilation factors....
More
|
|