Numerical Simulation of Convective-Radiative Heat Transfer in a Solar Chimney

2014 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Gianluca Tartaglione
Keyword(s):  
Kinetic Energy ◽  
Electrical Power ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Three Dimensional Model ◽  
Solar Chimney ◽  
Ansys Fluent ◽  
Heating And Cooling ◽  
Air Stream

Solar chimney is a new method to produce electrical power. It employs solar radiation to raise the temperature of the air and the buoyancy of warm air to accelerate the air stream flowing through the system. By converting thermal energy into the kinetic energy of air movement, solar chimneys have a number of different applications such as ventilation, passive solar heating and cooling of buildings, solar-energy drying, and power generation. Moreover, it can be employed as an energy conversion system from solar to mechanical. A component, such as a turbine or piezoelectric component, set in the path of the air current, converts the kinetic energy of the flowing air into electricity. In this paper, a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0.20 m for the vertical parallel walls configuration and at the inlet 0.34 m and at the outlet 0.20 m for convergent configuration. The chimney consists of a converging channel with one vertical wall and one inclined of 2°. The analysis is carried out on a three-dimensional model in airflow and the governing equations are given in terms of k-ε turbulence model. The problem is solved by means of the commercial code Ansys-Fluent. The numerical analysis was intended to examine the effect of the solar chimney’s height and spacing. Further, comparison between radiative and non-radiative model is examined and discussed. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles for a uniform wall heat flux on the vertical wall equal to 300 W/m2. Thermal and fluid dynamics behaviors are evaluated in order to have some indications to improve the energy efficiency of the system.

Numerical Investigation on Thermal and Fluid Dynamic Analysis of a Solar Chimney in a Building Façade

2019 ◽  
Author(s):  
Bernardo Buonomo ◽  
Furio Cascetta ◽  
Alessandra Diana ◽  
Oronzio Manca ◽  
Sergio Nardini
Keyword(s):  
Steady State ◽  
Numerical Investigation ◽  
Fluid Dynamic ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Geographical Location ◽  
Temperature Fields ◽  
Three Dimensional Model ◽  
Solar Chimney ◽  
Transient Regimes

Abstract Solar chimney is a system to produce energy and it has several applications, such as production of electricity, buildings ventilation, heating and cooling. In this paper, a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The chimney is 4.0 m high, 1.5 m wide whereas the thickness at the inlet the channel has a gap equal to 0.34 m and at the outlet it is 0.20 m. The chimney consists of a converging channel with one vertical wall and one inclined of 2°. The analysis is carried out on a three-dimensional model in airflow and the governing equations are given in terms of k-ε turbulence model. The problem is solved by means of the commercial code Ansys-Fluent. Simulations are carried out considering the solar irradiance for assigned geographical location and for a daily distribution. Further, comparison between steady state and transient regimes is examined and discussed. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles. Performances are better when heat flux is higher and sun is in front of chimney and a low-emissivity glass improves solar chimney achievements. Analysis in transient regimes confirm results obtained in steady state regime.

Visualization and Prediction of Natural Convection of Water Near Its Density Maximum in a Tall Rectangular Enclosure at High Rayleigh Numbers

2000 ◽  
Vol 123 (1) ◽  
pp. 84-95 ◽  
Author(s):  
C. J. Ho ◽  
F. J. Tu
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Convection Flow ◽  
Oscillatory Convection ◽  
Uniform Temperature ◽  
Density Maximum ◽  
Rectangular Enclosure ◽  
Rayleigh Numbers

An experimental and numerical investigation is presented concerning the natural convection of water near its maximum-density in a differentially heated rectangular enclosure at high Rayleigh numbers, in which an oscillatory convection regime may arise. The water in a tall enclosure of Ay=8 is initially at rest and at a uniform temperature below 4°C and then the temperature of the hot vertical wall is suddenly raised and kept at a uniform temperature above 4°C. The cold vertical wall is maintained at a constant uniform temperature equal to that of the initial temperature of the water. The top and bottom walls are insulated. Using thermally sensitive liquid crystal particles as tracers, flow and temperature fields of a temporally oscillatory convection was documented experimentally for RaW=3.454×105 with the density inversion parameter θm=0.5. The oscillatory convection features a cyclic sequence of onset at the lower quarter-height region, growth, and decay of the upward-drifting secondary vortices within counter-rotating bicellular flows in the enclosure. Two and three-dimensional numerical simulations corresponding to the visualization experiments are undertaken. Comparison of experimental with numerical results reveals that two-dimensional numerical simulation captures the main features of the observed convection flow.

scholarly journals NUMERICAL SIMULATION OF AIRFLOW AROUND VEHICLE MODELS

2018 ◽  
Vol 56 (3) ◽  
pp. 370
Author(s):  
Nguyen Van Thang ◽  
Ha Tien Vinh ◽  
Bui Dinh Tri ◽  
Nguyen Duy Trong
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Forces ◽  
Dissipation Energy ◽  
Ansys Fluent ◽  
Car Model ◽  
Airflow Field ◽  
Fluent Software

This article carries out the numerical simulation of airflow over three dimensional car models using ANSYS Fluent software. The calculations have been performed by using realizable k-e turbulence model. The external airflow field of the simplified BMV M6 model with or without a wing is simulated. Several aerodynamic characteristics such as pressure distribution, velocity contours, velocity vectors, streamlines, turbulence kinetic energy and turbulence dissipation energy are analyzed in this study. The aerodynamic forces acting on the car model is calculated and compared with other authors.

Numerical Calculation of Three-Dimensional Turbulent Natural Convection in a Cubical Enclosure Using a Two-Equation Model for Turbulence

1986 ◽  
Vol 108 (4) ◽  
pp. 806-813 ◽  
Author(s):  
H. Ozoe ◽  
A. Mouri ◽  
M. Hiramitsu ◽  
S. W. Churchill ◽  
N. Lior
Keyword(s):  
Natural Convection ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Spiral Flow ◽  
Vertical Side ◽  
Turbulent Natural Convection ◽  
Cubical Enclosure ◽  
Side Walls

This paper presents a model and numerical results for turbulent natural convection in a cubical enclosure heated from below, cooled on a portion of one vertical side wall and insulated on all other surfaces. Three-dimensional balances were derived for material, energy, and the three components of momentum, as well as for the turbulent kinetic energy k and the rate of dissipation of turbulent kinetic energy ε. The constants used in the model were the same as those used by Fraikin et al. for two-dimensional convection in a channel. Illustrative transient calculations were carried out for Ra = 106 and 107 and Pr = 0.7. Both the dominant component of the vector potential and the Nusselt number were found to converge to a steady state. Isothermal lines and velocity vectors for vertical cross sections normal to the cooled wall indicated three-dimensional effects near the side walls. A top view of the velocity vectors revealed a downward spiral flow near the side walls along the cooled vertical wall. A weak spiral flow was also found along the side walls near the wall opposing the partially cooled one. The highest values of the eddy diffusivity were 2.6 and 5.8 times the molecular kinematic viscosity for Ra = 106 and 107, respectively. A coaxial double spiral movement, similar to that previously reported for laminar natural convection, was found for the time-averaged flow field. This computing scheme is expected to be applicable to other thermal boundary conditions.

Numerical Investigation of Combined Top and Lateral Blowing in a Peirce-Smith Converter

2013 ◽  
Vol 8 (2) ◽  
pp. 119-127 ◽  
Author(s):  
D. K. Chibwe ◽  
G. Akdogan ◽  
P. Taskinen
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Slag Layer ◽  
Wave Formation ◽  
Process Efficiency ◽  
Phase System ◽  
Ansys Fluent ◽  
Contour Plots

Abstract Typical current operation of lateral-blown Peirce-Smith converters (PSCs) has the common phenomenon of splashing and slopping due to air injection. The splashing and wave motion in these converters cause metal losses and potential production lost time due to intermittent cleaning of the converter mouth and thus reduced process throughput. Understanding of the effect of combined top and lateral blowing could possibly lead to alternative technology advancement for increased process efficiency. In this study, computational fluid dynamics (CFD) simulations of conventional common practice (lateral blowing) and combined (top and lateral blowing) in a PSC were carried out, and results of flow variables (bath velocity, turbulence kinetic energy, etc.) were compared. The two-dimensional (2-D) and three-dimensional (3-D) simulations of the three-phase system (air–matte–slag) were executed utilizing a commercial CFD numerical software code, ANSYS FLUENT 14.0. These simulations were performed employing the volume of fluid and realizable turbulence models to account for multiphase and turbulent nature of the flow, respectively. Upon completion of the simulations, the results of the models were analysed and compared by means of density contour plots, velocity vector plots, turbulent kinetic energy vector plots, average turbulent kinetic energy, turbulent intensity contour plots and average matte bulk velocity. It was found that both blowing configuration and slag layer thickness have significant effects on mixing propagation, wave formation and splashing in the PSC as the results showed wave formation and splashing significantly being reduced by employing combined top- and lateral-blowing configurations.

Laminar Natural Convection in a Discretely Heated Cavity: I—Assessment of Three-Dimensional Effects

1995 ◽  
Vol 117 (4) ◽  
pp. 902-909 ◽  
Author(s):  
T. J. Heindel ◽  
S. Ramadhyani ◽  
F. P. Incropera
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Companion Paper ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Laminar Natural Convection

Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 × 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios Ahtr ≲ 3, average Nusselt numbers increased with decreasing Ahtr. However, for Ahtr ≳ 3, the two and three-dimensional predictions were within 5 percent of each other and results were approximately independent of Ahtr. In a companion paper (Heindel et al., 1995a), predictions are compared with experimental results and heat transfer correlations are developed.

scholarly journals Performance of drop shaped pin fin heat exchanger with four different fin dimensions

2020 ◽  
Vol 14 (2) ◽  
pp. 6934-6951
Author(s):  
A.A. Mohamed ◽  
Obai Younis
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Surface Area ◽  
Three Dimensional ◽  
Tail Length ◽  
Ansys Fluent ◽  
Frictional Loss ◽  
Pin Fin ◽  
Heating And Cooling ◽  
Wetted Surface Area

In engineering, there are two primary heat transfer procedures of fluids namely, heating and cooling within a conduit that are well recognized. The heat transfer literacy remains a core component to design the heat exchangers. The study aims to present the consequences of drop shaped pin fin hear exchanger performance with four different fin dimensions. A rectangular duct with different drop-shaped pin fins dimensions is present in the heat exchanger, having similar heat transfer wetted surface area. ANSYS FLUENT 14.5 conducted three-dimensional finite volume to select the optimum pin fin dimension. The numerical results for the four cases L/D 1, 1.25, 1.5 and 1.75 indicated heat transfer had no effect on the variations in pin tail length; however, it affected frictional losses or pressure drop. There is significant decrease in the frictional loss as the result of increase in the pin tail length. The pun fin drop showed significant decrease in friction power, unlike the round pins. The ratio of pin height to the cylindrical portion of the pin (H/D) had major impact on the wetted surface area, which affects the rate of heat transfer.  

scholarly journals Prediction of Indoor Air Circulation of Residential Room with Adaptation of Solar Chimney Using Numerical Technique

2019 ◽  
Vol 8 (11) ◽  
pp. 4110-4116
Keyword(s):  
Air Temperature ◽  
Cooling System ◽  
Residential Buildings ◽  
Numerical Technique ◽  
Electrical Power ◽  
Air Gap ◽  
Solar Chimney ◽  
Heating And Cooling ◽  
Gap Width ◽  
Ventilation Velocity

With the exponential increase in consumption of electrical power during the summer season by household, there is a great need for households to withhold sustainability. To maintain the temperature of the household a passive heating and cooling system is used i.e. Solar Chimney. Ventilation, through a natural convection process, is gaining a lot of attention to be an alternative technique for mechanical air conditioning ventilation because of its reduced power usage when compared to the external cooling devices used in residential buildings of hot regions. The present study, involve solar chimney of horizontal and vertical designs in comparison with different width and height. The following paper studies the effect of a solar chimney on the indoor thermal behavior using Numerical Technique for a prototype of a residential room. The performance on the ventilation velocity and air temperature operation inside the room with varying air gap width is studied based on multiple numerical analysis solutions. The present study deals with two different architectures of a two dimensional model and results have shown that the ventilation velocity has increased to 0.017626444 kg/s and operative air temperature has been decreased by 7.26ºC for the vertical model while the horizontal model has shown a mass flow rate of 0.018027636 kg/s and a temperature decrease of 9.15ºC. The most efficient chimney was found to be model 7 which is horizontal solar chimney 3 with an air gap width of 0.05625m and a height of 0.3175 m, when compared to the other models from model number one to six.

Effect of the number of turbine blades on the air flow within a solar chimney power plant

2017 ◽  
Vol 232 (4) ◽  
pp. 425-436 ◽  
Author(s):  
Ahmed Ayadi ◽  
Zied Driss ◽  
Abdallah Bouabidi ◽  
Mohamed Salah Abid
Keyword(s):  
Power Plant ◽  
Kinetic Energy ◽  
Power Plants ◽  
Turbulent Viscosity ◽  
Air Flow ◽  
Turbine Blades ◽  
Electrical Power ◽  
Thermal Characteristics ◽  
Solar Chimney ◽  
Solar Chimney Power Plant

Solar chimney power plants generate thermal heat and electrical power using the radiation from sun. These systems are characterized by their high costs. In fact, it is required to optimize the components of the solar system such as the collector, the chimney, the absorber, and the turbine. This paper focuses on the effect of the number of turbine blades on the air flow within a small prototype of a solar chimney power plant. Four configurations with different turbine blades are proposed to study the effect of the turbine blades number on the thermal characteristics of a solar chimney power plant. For each configuration, the distribution of the magnitude velocity, the air temperature, the pressure, the turbulent kinetic energy, and the turbulent viscosity are presented and discussed. This paper is identified to be of interest for engineers and designers for increasing the power output of a solar chimney power plant.

scholarly journals Nonaxisymmetric Effects for Three-Dimensional Analysis of a Brake

1994 ◽  
Vol 116 (3) ◽  
pp. 401-407 ◽  
Author(s):  
A. Floquet ◽  
M. C. Dubourg
Keyword(s):  
Finite Element Method ◽  
Heat Flux ◽  
Three Dimensional ◽  
Computer Time ◽  
Temperature Fields ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Fem Method ◽  
Validation Tests ◽  
Transient Heat Flux

A three-dimensional model of axisymmetric moving solids submitted to nonaxisymmetric transient heat flux conditions is presented in this paper. Temperature fields are obtained using a new hybrid FFT-FEM method that combines Fourier transform techniques and finite element method. A fast Fourier form algorithm is used which leads to inexpensive computer time. Validation tests are presented. Efficiency of the method is demonstrated.

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