Analysis of Melt Flows in an Electric Heating Furnace for Quartz Glass Synthesis

2018 ◽  
Author(s):  
Qianli Ma ◽  
Haisheng Fang ◽  
Chunli Shang ◽  
Zhongyi Liu ◽  
Jing Wang
Keyword(s):  
Natural Convection ◽  
Flow Field ◽  
Flow Pattern ◽  
Quartz Glass ◽  
Flow Behavior ◽  
Electric Heating ◽  
Heating Furnace ◽  
Rotating Speed ◽  
Wide Range ◽  
Bubble Transport

Flow patterns in molten quartz are highly related to the bubble transport and removal. Understanding the flow behavior in molten quartz is of great importance to the manufacture of high-purity quartz glass. In this paper, a numerical model is set up to simulate the flow field of molten quartz in a typical electric heating furnace. Natural convection and Marangoni convection are examined for their respective effects on the flow pattern of molten quartz. Different heater arrangements will change the flow field by varying temperature distributions. Top heating and bottom heating have the same vortex direction; while side heating induces an opposite direction to them. To improve the flow field in molten quartz, forced convection is introduced by crucible rotation. The influences of rotating speed of crucible on the flow field are studied in a wide range varying from 0 to 100 rad/s. With the increase of rotating speed, a reverse vortex to natural convection shows in molten quartz; and the velocity magnitude increase at a growing speed. To find out the optimal flow pattern for quartz glass manufacture, a qualitative analysis is presented on the reliance of bubble transport behavior on the convection modes. Based on the results, useful suggestions are provided towards increasing the bubble-free area of molten quartz and improving the quality of quartz glass.

Experimental and Numerical Study for Improved Understanding of Mixed-Convection Type of Flows in Turbine Casing Cavities During Shut-Down Regimes

2021 ◽  
Author(s):  
Oguzhan Murat ◽  
Budimir Rosic ◽  
Koichi Tanimoto ◽  
Ryo Egami
Keyword(s):  
Natural Convection ◽  
Flow Field ◽  
Mixed Convection ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Scale Model ◽  
Unsteady Temperature ◽  
Numerical Predictions ◽  
Wide Range ◽  
Turbine Casing

Abstract Due to increase in the power generation from renewable sources, steam and gas turbines will be required to adapt for more flexible operations with frequent start-ups and shut-downs to provide load levelling capacity. During shut-down regimes, mixed convection takes place with natural convection dominance depending on the operating conditions in turbine cavities. Buoyant flows inside the turbine that are responsible for non-uniform cooling leading to thermal stresses and compromise clearances directly limits the operational flexibility. Computational fluid dynamics (CFD) tools are required to predict the flow field during these regimes since direct measurements are extremely difficult to conduct due to the harsh operating conditions. Natural convection with the presence of cross-flow -mixed convection has not been extensively studied to provide detailed measurements. Since the literature lacks of research on such flows with real engine representative operating conditions for CFD validation, the confidence in numerical predictions is rather inadequate. This paper presents a novel experimental facility that has been designed and commissioned to perform very accurate unsteady temperature and flow field measurements in a simplified turbine casing geometry. The facility is capable of reproducing a wide range of Richardson, Grashof and Reynolds numbers which are representative of engine realistic operating conditions. In addition, high fidelity, wall resolved LES with dynamic Smagorinsky subgrid scale model has been performed. The flow field as well as heat transfer characteristics have been accurately captured with LES. Lastly, inadequacy of RANS for mixed type of flows has been highlighted.

Natural Convection Liquid Cooling of a Substrate-Mounted Protrusion in a Square Enclosure: A Parametric Study

1992 ◽  
Vol 114 (2) ◽  
pp. 401-409 ◽  
Author(s):  
S. B. Sathe ◽  
Y. Joshi
Keyword(s):  
Natural Convection ◽  
Boundary Conditions ◽  
Flow Behavior ◽  
Air Cooling ◽  
Square Enclosure ◽  
Simple Boundary ◽  
Wide Range ◽  
Solid Region ◽  
Rayleigh Numbers ◽  
Thermal Conductivities

The coupled conduction and natural convection transport from a substrate-mounted heat generating protrusion in a liquid-filled square enclosure is numerically examined. The governing steady two-dimensional equations are solved using a finite-difference method for a wide range of Rayleigh numbers, protrusion thermal conductivities and widths, substrate heights, and enclosure boundary conditions. The results presented apply to liquids with 10≤Pr≤1000. It was established that in many situations it may be inappropriate to specify simple boundary conditions on the solid surface and decouple the conduction within the substrate or the protrusion. Higher Rayleigh numbers, protrusion thermal conductivities, and widths enhanced cooling. A variation in the substrate height did not affect the maximum protrusion temperature; however, the flow behavior was considerably altered. An empirical correlation for the maximum protrusion temperature was developed for a wide range of parametric values. The enclosure thermal boundary conditions changed the heat transfer in the solid region to only a small extent. Immersion cooling in common dielectric liquids was shown to be advantageous over air cooling only if the thermal conductivity of the protrusion was larger than that of the liquid.

Computational Investigation of the Flow Field Inside an Submersible Tubular Pump

2011 ◽  
Author(s):  
Yan Jin ◽  
Chao Liu ◽  
Jiren Zhou ◽  
Fangping Tang
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Optimization Design ◽  
High Efficiency ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Rotating Speed ◽  
Pumping System ◽  
Wide Range ◽  
Engineering Costs

Submersible tubular pump is particularly suitable for ultra-low head (net head less than 2 m) pumping station which can reduce the excavation depth, lower engine room height, simplify hydraulic structure, and save civil engineering costs. Submersible tubular pump with smaller motor unit can reduce the flow resistance. The flow field inside the submersible tubular pump is simulated in a commercial computation fluid dynamics (CFD) code FLUENT. The RNG k-ε turbulent model and SIMPLE algorithm are applied to analyze the full passage of a submersible tubular pump, the performance of pump such as head, shaft power and efficiency are predicted based on the calculation of different operating conditions. The simulations are carried out over a wide range of operating points, from 0.8 of the reference mass flow rate at the best efficiency point (BEP) to the 1.28 of the BEP flow rate at the same rotating speed. For verifying the accuracy and reliability of the calculation results, a model test is conducted. The comparison of simulation results and the experiment data show that the calculation performances are agree with the experiment results in the high efficiency area and large discharge condition, but in the condition of low discharge, it exists deviations between the two results. Compare with the numerical simulation and experiment, which can provide more evidences for the hydraulic performance prediction and optimization design of submersible tubular pump pumping system.

Optimization design of submerged propeller in oxidation ditch by computational fluid dynamics and comparison with experiments

2016 ◽  
Vol 74 (3) ◽  
pp. 681-690 ◽  
Author(s):  
Yuquan Zhang ◽  
Yuan Zheng ◽  
E. Fernandez-Rodriguez ◽  
Chunxia Yang ◽  
Yantao Zhu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Energy Consumption ◽  
Flow Field ◽  
Flow Pattern ◽  
Operating Conditions ◽  
Oxidation Ditch ◽  
Actual Measurement ◽  
Operating Condition ◽  
Rotating Speed

The operating condition of a submerged propeller has a significant impact on flow field and energy consumption of the oxidation ditch. An experimentally validated numerical model, based on the computational fluid dynamics (CFD) tool, is presented to optimize the operating condition by considering two important factors: flow field and energy consumption. Performance demonstration and comparison of different operating conditions were carried out in a Carrousel oxidation ditch at the Yingtang wastewater treatment plants in Anhui Province, China. By adjusting the position and rotating speed together with the number of submerged propellers, problems of sludge deposit and the low velocity in the bend could be solved in a most cost-effective way. The simulated results were acceptable compared with the experimental data and the following results were obtained. The CFD model characterized flow pattern and energy consumption in the full-scale oxidation ditch. The predicted flow field values were within −1.28 ± 7.14% difference from the measured values. By determining three sets of propellers under the rotating speed of 6.50 rad/s with one located 5 m from the first curved wall, after numerical simulation and actual measurement, not only the least power density but also the requirement of the flow pattern could be realized.

Experimental and Numerical Study for Improved Understanding of Mixed-Convection Type of Flows in Turbine Casing Cavities During Shut-Down Regimes

2021 ◽  
Author(s):  
Oguzhan Murat ◽  
Budimir Rosic ◽  
Koichi Tanimoto ◽  
Ryo Egami
Keyword(s):  
Natural Convection ◽  
Flow Field ◽  
Mixed Convection ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Scale Model ◽  
Unsteady Temperature ◽  
Numerical Predictions ◽  
Wide Range ◽  
Turbine Casing

Abstract Due to increase in the power generation from renewable sources, steam and gas turbines will be required to adapt for more flexible operations with frequent start-ups and shut-downs to provide load levelling capacity. During shut-down regimes, mixed convection takes place with natural convection dominance depending on the operating conditions in turbine cavities. Buoyant flows inside the turbine that are responsible for non-uniform cooling leading to thermal stresses and compromise clearances directly limits the operational flexibility. Computational fluid dynamics (CFD) tools are required to predict the flow field during these regimes since direct measurements are extremely difficult to conduct due to the harsh operating conditions. Natural convection with the presence of cross-flow -mixed convection has not been extensively studied to provide detailed measurements. Since the literature lacks of research on such flows with real engine representative operating conditions for CFD validation, the confidence in numerical predictions is rather inadequate. This paper presents a novel experimental facility that has been designed and commissioned to perform very accurate unsteady temperature and flow field measurements in a simplified turbine casing geometry. The facility is capable of reproducing a wide range of Richardson, Grashof and Reynolds numbers which are representative of engine realistic operating conditions. In addition, high fidelity, wall resolved LES with dynamic Smagorinsky subgrid scale model has been performed. The flow field as well as heat transfer characteristics have been accurately captured with LES. Lastly, inadequacy of RANS for mixed type of flows has been highlighted.

scholarly journals Comparing Internal Flow in Freezing and Evaporating Water Droplets Using PIV

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1489
Author(s):  
Linn Karlsson ◽  
Anna-Lena Ljung ◽  
T. Staffan Lundström
Keyword(s):  
Natural Convection ◽  
Marangoni Convection ◽  
Flow Direction ◽  
Flow Behavior ◽  
Internal Flow ◽  
Freezing Process ◽  
Complex Nature ◽  
Water Droplets ◽  
Wide Range ◽  
Jet Printing

The study of evaporation and freezing of droplets is important in, e.g., spray cooling, surface coating, ink-jet printing, and when dealing with icing on wind turbines, airplane wings, and roads. Due to the complex nature of the flow within droplets, a wide range of temperatures, from freezing temperatures to heating temperatures, have to be taken into account in order to increase the understanding of the flow behavior. This study aimed to reveal if natural convection and/or Marangoni convection influence the flow in freezing and evaporating droplets. Droplets were released on cold and warm surfaces using similar experimental techniques and setups, and the internal flow within freezing and evaporating water droplets were then investigated and compared to one another using Particle Image Velocimetry. It was shown that, for both freezing and evaporating droplets, a shift in flow direction occurs early in the processes. For the freezing droplets, this effect could be traced to the Marangoni convection, but this could not be concluded for the evaporating droplets. For both evaporating and freezing droplets, after the shift in flow direction, natural convection dominates the flow. In the end of the freezing process, conduction seems to be the only contributing factor for the flow.

scholarly journals NATURAL CONVECTION IN RECTANGULAR CAVITIES WITH DIFFERENT ASPECT RATIOS

2011 ◽  
Vol 10 (1-2) ◽  
pp. 44
Author(s):  
R. M. Nogueira ◽  
M. A. Martins ◽  
F. Ampessan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Flow Behavior ◽  
Heated Wall ◽  
Flow Profile ◽  
Height Ratio ◽  
Dimensionless Variable ◽  
Aspect Ratios ◽  
Wide Range

Natural convection in closed cavities has been extensively studied in recent decades. This spontaneous method of heat transfer has a wide range of applications in engineering. In the present work, natural convection was numerically analyzed in a rectangular cavity heated on one of the sides and cooled on the opposite side. Temperatures of the heated wall and of the cooled wall were assumed to be constant. The objective of these studies was to determine the effects of the aspect ratio and the Rayleigh number on flow behavior and heat transfer in the cavity. In the simulations, the Rayleigh number drastically influenced the flow profile and heat transfer inside de cavity, as well as the thickness of the thermal boundary layer. It was also verified that the Nusselt number is strongly dependent on the L/D (Length/Height) ratio, and that this dimensionless variable increases with the increase of the W/L. The simulation of natural convection problems in the CFD Studio satisfactorily described the studied situations.

Numerical and Experimental Investigation of an Aerodynamically High-Loaded Axial Boiler Fan

2000 ◽  
Author(s):  
A. Reischke ◽  
M. Jung ◽  
P. Breuhaus ◽  
J. Molin ◽  
S. Hess
Keyword(s):  
Flow Field ◽  
Guide Vane ◽  
Flow Behavior ◽  
Fast Response ◽  
Turnaround Time ◽  
Design System ◽  
Viscous Effects ◽  
Wide Range ◽  
Hot Film ◽  
Hot Film Anemometry

In a common project ABB Fläkt Industri AB, Sweden, and ABB Turbo Systems Ltd., Switzerland, developed a Q3D design system for low Mach number axial fans. In order to validate the Q3D-calculations and the customized loss correlation, the flow field of an industrial high-pressure boiler fan was investigated experimentally. The examined single stage fan is equipped with hydraulically adjustable rotor blades, non-profiled guide vanes and an annular diffuser. Varying the stagger angle between 34° and 76° allows operating the fan over a wide range of volume flows. Experiments and calculations cover the entire stable operating range. Flow field traverses by means of hot film anemometry and pneumatic total pressure Kiel probes at different sections within the rotor/vane configuration, combined with axially and tangentially distributed static pressures tabs and fix mounted Kiel probes, allowed a deep insight in the flow behavior. The fast response capability of the hot film anemometry was used to measure the flow field downstream of the rotor in detail. Additionally, flow field visualizations inside the guide vane channel based upon a TiO4/Oil-paint technique completed the experimental fan investigation. The Q3D system is based on coupling the Euler codes MISES (S1) and MTFlow (S2), both developed at MIT. Loss models were implemented to account for profile losses, leakage losses and endwall losses. Near wall viscous effects are considered by boundary layer modeling. The investigations show that the S1/S2 Euler solvers behave well even in case of Mach numbers below 0.03. S1 convergence problems arise for off-design cases because of unfavorable incidence angles. The fully automated Q3D systems allows calculating fan performance charts with low turnaround time in good agreement with the measurement.

scholarly journals Experimental Flow Field Investigation of the Bio-Inspired Corrugated Wing for MAV Applications

2021 ◽  
Vol 13 (2) ◽  
pp. 37-50
Author(s):  
Y. D. DWIVEDI ◽  
ABHISHEK MOHAPATRA ◽  
T. BLESSINGTON ◽  
Md IRFAN
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
Flow Pattern ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Lower Surface ◽  
Field Investigation ◽  
Low Reynolds ◽  
Air Vehicles

This is an experimental flow field study of a bio-inspired corrugated finite wing from the dragonfly intended to assess the flow behavior over the wing and compare it with a wing of the same geometry with filled corrugation, at low Reynolds numbers 46000 and 67000. The work purpose is to explore the potential application of such types of wings for Micro Air Vehicles (MAVs) or micro sized Unmanned Air Vehicles (UAVs). Two types of wings are taken into account: first wing was a bio-inspired corrugated wing which was obtained from the mid span of the dragonfly, and the second wing was the same geometry with filled corrugation. Both wings were fabricated by using 3-D printing machine. The tufts were glued at three different locations i.e. at center, 30%, and 60% of the semi-span towards the right side of the wing at the trailing edge. The boundary layers were measured by using boundary layer rakes inside the open-end low speed wing tunnel with varied angles of attack. The results of the tuft flow visualization showed that the flow pattern at different span locations was different at different angles of attack and different wing velocities (Reynolds number). The fluctuations of the two different wings at the same angle of attack and Reynolds number were found different. Also, the directions of the flow for both wings were found to be different at different span locations. The boundary layer measurement results for both wings were found to be different at the same angles of attack and Reynolds numbers. The flow pattern also showed that the wing’s upper as well as lower surface behaved differently on the same wing under the same measurement conditions. The results showed that the corrugated wing outperformed the conventional wing at low Reynolds number and the stall angle of the corrugated wing was more than the conventional wing.

URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

2020 ◽  
Vol 4 (1) ◽  
pp. 45
Author(s):  
Elahe Mirabi ◽  
Nasrollahi Nazanin
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Natural Ventilation ◽  
Flow Behavior ◽  
Air Flow ◽  
Urban Geometry ◽  
Wide Range ◽  
Low Energy Buildings ◽  
Outdoor Comfort ◽  
Solar Access

<p>Designing urban facades is considered as a major factor influencing issues<br />such as natural ventilation of buildings and urban areas, radiations in the<br />urban canyon for designing low-energy buildings, cooling demand for<br />buildings in urban area, and thermal comfort in urban streets. However, so<br />far, most studies on urban topics have been focused on flat facades<br />without details of urban layouts. Hence, the effect of urban facades with<br />details such as the balcony and corbelling on thermal comfort conditions<br />and air flow behavior are discussed in this literature review. <strong>Aim</strong>: This<br />study was carried out to investigate the effective factors of urban facades,<br />including the effects of building configuration, geometry and urban<br />canyon’s orientation. <strong>Methodology and Results</strong>: According to the results,<br />the air flow behavior is affected by a wide range of factors such as wind<br />conditions, urban geometry and wind direction. Urban façade geometry<br />can change outdoor air flow pattern, thermal comfort and solar access.<br /><strong>Conclusion, significance and impact study</strong>: In particular, the geometry of<br />the facade, such as indentation and protrusion, has a significant effect on<br />the air flow and thermal behavior in urban facades and can enhance<br />outdoor comfort conditions. Also, Alternation in façade geometry can<br />affect pedestrians' comfort and buildings energy demands.</p>

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