Virtual Height Aided Solar Chimney: A New Design

2011 ◽  
Author(s):  
Khaled I. E. Ahmed ◽  
Ali K. Abdel-Rahman ◽  
Mahmoud Ahmed ◽  
Wael M. Khairaldien
Keyword(s):  
Electric Power ◽  
Co2 Emissions ◽  
Conversion Efficiency ◽  
Numerical Study ◽  
Air Flow ◽  
Flow Speed ◽  
Numerical Results ◽  
Solar Chimney ◽  
Virtual Height ◽  
Wide Range

Renewable energy source deployment is growing rapidly as it reduces CO2 emissions and increases diversity and security of supply. Solar chimney (SC) is a promising large-scale power technology, which absorbs solar radiation and converts parts of solar energy into electric power free of CO2 emissions. A major problem of Solar Chimney Power Plant (SCPP) is its low conversion efficiency as determined by the thermal performance of the system. However, the conversion efficiency of SCPP significantly increases with the SC height increase. The current paper proposes a new design of a virtual height aided solar chimney. In this new system the solar chimney is aided with a passive cooling system at the top of the chimney and a passive solar heater at its base to virtually mimic larger heights of the chimney. The new design has been simulated numerically for development and optimization. The numerical study is done in two stages to examine this concept. In the first stage, numerical results are obtained for the effect of the chimney height on the inside air flow speed. Then, in the second stage, the effect of decreasing the temperature at the chimney exit and the effect of increasing the temperature at the chimney base on the air flow speed are examined separately for small chimney heights. Then the combined effect of the two actions is investigated at a wide range of chimney heights. The numerical results have shown that the localized base heating and exit cooling have significantly enhanced the chimney performance for chimney heights up to 500m. A chimney with height of 300m gains an increase in the air velocity more than 25% due to the heating and cooling actions. Virtual height aided Chimney with original height of 300m acts similarly to a conventional chimney with height of 500m due to the effect of base heating and exit cooling actions. This air flow velocity increase reflects 100% increase in the expected generated electric power. Further detailed results are presented and discussed.

Fluid Flow and Lateral Fluid Dispersion in Bounded Granular Beds

2002 ◽  
Author(s):  
Azita Soleymani ◽  
Eveliina Takasuo ◽  
Piroz Zamankhan ◽  
William Polashenski
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Numerical Results ◽  
Transition To Turbulence ◽  
Wide Range

Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through random packing of nonoverlapping spheres at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study (Fand et al., 1987). This observation suggests that no transition to turbulence could occur in the range of Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of the lateral dispersivity of solute continuously injected into a three-dimensional bounded granular bed at moderate Peclet numbers. Lateral fluid dispersion coefficients are calculated by comparing the concentration profiles obtained from numerical and analytical methods. Comparing the present numerical results with data available in the literature, no evidence has been found to support the speculations by others for a transition from laminar to turbulent regimes in porous media at a critical Reynolds number.

Numerical Modeling of Buoyancy Induced Convection in Finned Heat Sinks in Presence of Unheated and Heated Shrouds

2005 ◽  
Author(s):  
S. S. Bahga ◽  
A. Bhattacharya ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Sink ◽  
Numerical Study ◽  
Numerical Results ◽  
Heat Sinks ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Wide Range ◽  
The Impact

This paper investigates the effects of the presence of unheated and heated shrouds on the thermal performance of longitudinal finned heat sinks. A comprehensive numerical study was conducted to determine the impact of the shroud clearance from the tip of the fins and shroud heating. The first part of the study deals with the effects of an unheated shroud on finned heat sinks of different fin height, fin pitch and length in an attempt to cover a wide range of geometry. The numerical results reveal an optimum clearance for maximum heat transfer. For all heat sinks studied the unheated shroud improved the performance by as much as 15% until the shroud was very close when the performance decreased by as much as 10%. In the second part of the paper, the effects of heating of the shroud were considered. In these numerical runs, an isothermal boundary condition was imposed on the shroud. For the heating levels considered, it was found that heating of the shrouds can increase or lower the thermal performance of the heat sink depending on the heat sink geometry and shroud clearance. Finally, the numerical results also revealed a systematic dependence of the normalized Nusselt number on the Rayleigh number for a given heat sink geometry.

Numerical Simulation on the Characteristic of a Solar Chimney

2012 ◽  
Vol 614-615 ◽  
pp. 712-715 ◽  
Author(s):  
Xun Wang ◽  
Yong Gang Lei ◽  
Fei Wang ◽  
Jun Qin Hou
Keyword(s):  
Solar Radiation ◽  
Heat Transfer Performance ◽  
Air Flow ◽  
Research Result ◽  
Ventilation Rate ◽  
Flow Speed ◽  
Cover Plate ◽  
Solar Chimney ◽  
Flow And Heat Transfer ◽  
Width Direction

The air flow and heat transfer performance of a solar chimney with the inclination angle of 30deg was investigated by using numerical method. It was found that there is a correlation between solar radiation and ventilation rate and there is a temperature field under the effect of thermal pressure. The research result shows that in the certain scope of research, the ventilation rate is influenced by solar radiation. With the solar radiation increasing, the temperature of chimney decrease along direction from the heat absorption wall to the glass cover-plate surface, and the air flow speed distribute nonuniform along the channel width direction.

A Numerical Study of the Shape of the Surface Separating Flow Into Branches in Microvascular Bifurcations

1992 ◽  
Vol 114 (3) ◽  
pp. 398-405 ◽  
Author(s):  
G. Enden ◽  
A. S. Popel
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Vessel Diameter ◽  
Numerical Results ◽  
Navier Stokes ◽  
Parent Vessel ◽  
Blood Constituents ◽  
Separating Flow ◽  
Wide Range

The shape of the separating surface formed by the streamlines entering the branches of microvascular bifurcations plays a major role in determining the distribution of red blood cells and other blood constituents downstream from the bifurcation. Using the finite element method, we determined the shape of the surface through numerical solution of three dimensional Navier-Stokes equations for fluid flow at low Reynolds numbers in a T-type bifurcation of circular tubes. Calculations were done for a wide range of daughter branch to parent vessel diameter ratios and flow ratios. The effect of Reynolds number was also studied. Our numerical results are in good agreement with previously reported experimental data of Rong and Carr (Microvascular Research, Vol. 39, pp. 186-202, 1990). The numerical results of this study will be used to predict the concentration of blood constituents downstream from microvascular bifurcations providing that the inlet concentration profile is known.

scholarly journals Numerical Investigation of Combined Buoyancy and Surface Tension Driven Convection in an Axi-Symmetric Cylindrical Annulus

2007 ◽  
Vol 12 (4) ◽  
pp. 541-552 ◽  
Author(s):  
M. Sankar ◽  
M. Venkatachalappa
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Numerical Study ◽  
Relaxation Method ◽  
Numerical Results ◽  
Physical Parameters ◽  
Cylindrical Annulus ◽  
Wide Range ◽  
Contour Plots ◽  
Stream Function Formulation

A numerical study is conducted to understand the effect of surface tension on buoyancy driven convection in a vertical cylindrical annular cavity filled with a low Prandtl number fluid. The inner and outer cylinders are maintained at different uniform temperatures and the horizontal top and bottom walls are thermally insulated. The upper free surface is assumed to remain flat and non-deformable. A finite difference scheme consisting of the Alternating Direction Implicit method and the Successive Line Over Relaxation method is used to solve the vorticity stream function formulation of the problem. Detailed numerical results of heat transfer rate, temperature and velocity fields have been presented for a wide range of physical parameters of the problem. The flow pattern and temperature distribution in the annular cavity are presented by means of contour plots of streamlines and isotherms. The rate of heat transfer is estimated by evaluating the average Nusselt number. Further, the present numerical results are compared with the existing results and are found to be in good agreement.

Numerical and Qualitative Analysis of a Single Particle Behavior in a Shear Driven Flow in Equilateral Triangular Cavity

2013 ◽  
Vol 465-466 ◽  
pp. 557-561
Author(s):  
Muhammad Ammar Nik Mutasim ◽  
Nasir Ali ◽  
M.S. Idris ◽  
Ahmed N. Oumer
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Flow Speed ◽  
Numerical Results ◽  
Driven Cavity ◽  
The Past ◽  
Particle Flows ◽  
Equivalent Time ◽  
Surrounding Fluid ◽  
Good Agreement

Intesive research works have been done on solid particle flows for the past decades. However, prediction of accurate relationship between the particle and the surrounding fluid is still challenging. This study focuses on the experimental and numerical study of behavior of a particle flow in a lid-driven cavity of equilateral triangular shape. Numerical analysis was done using Finite Difference Method (FDM) with stream function vorticity approach. The center location of the fluid flow was treated assumed to be the particle motion. To check the validaty of the numerical results, experiment was done. The particle and fluid used for the experiment were water and silk, respectively. The particle is considered to be slightly buoyant towards water. In the experiment the fluid flow was based on horizontal translating motion where the particle was initially at rest at the bottom wall of the cavity. The fluid flow speed is set to laminar flow with Reynolds Number, Re = 0 to 1000. It was found that the silk particle moved to the preferential path of the primary vortex at equivalent time of 13 seconds. Generally, the experimetal and numerical results for the streamlines were in good agreement.

NUMERICAL STUDY OF HEAT TRANSFER AND AIR FLOW IN HEATED GREENHOUSES

2008 ◽  
Author(s):  
Nadia Dihmani ◽  
Ahmed Mezrhab ◽  
Larbi Elfarh ◽  
Hicham Bouali ◽  
Hassan Naji
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Air Flow

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>

Using Ansys for Design and Numerical Study of a Specific Fixed Wing UAV

2018 ◽  
Vol 55 (4) ◽  
pp. 652-657 ◽  
Author(s):  
Gabriel Murariu ◽  
Razvan Adrian Mahu ◽  
Adrian Gabriel Murariu ◽  
Mihai Daniel Dragu ◽  
Lucian P. Georgescu ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Unmanned Aerial Vehicle ◽  
Numerical Study ◽  
Flight Time ◽  
Cluster System ◽  
Numerical Results ◽  
Operational Performance ◽  
Gliding Flight ◽  
Aerial Vehicle ◽  
Constant Altitude

This article presents the design of a specific unmanned aerial vehicle UAV prototype own building. Our UAV is a flying wing type and is able to take off with a little boost. This system happily combines some major advantages taken from planes namely the ability to fly horizontal, at a constant altitude and of course, the great advantage of a long flight-time. The aerodynamic models presented in this paper are optimized to improve the operational performance of this aerial vehicle, especially in terms of stability and the possibility of a long gliding flight-time. Both aspects are very important for the increasing of the goals� efficiency and for the getting work jobs. The presented simulations were obtained using ANSYS 13 installed on our university� cluster system. In a next step the numerical results will be compared with those during experimental flights. This paper presents the main results obtained from numerical simulations and the obtained magnitudes of the main flight coefficients.

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