Radiative Effects on Mixed Convection in a Uniformly Heated Vertical Convergent Channel with an Unheated Moving Plate

2011 ◽  
Vol 3 (3) ◽  
pp. 280-296
Author(s):  
Assunta Andreozzi ◽  
Nicola Bianco ◽  
Vincenzo Naso
Keyword(s):  
Mixed Convection ◽  
Heat Removal ◽  
Polymeric Materials ◽  
Temperature Fields ◽  
Uniform Heat Flux ◽  
Radiative Effects ◽  
Moving Plate ◽  
Convergent Channel ◽  
Research Attention ◽  
Channel Configuration

AbstractFluids engineering is extremely important in a wide variety of materials processing systems, such as soldering, welding, extrusion of plastics and other polymeric materials, Chemical Vapor Deposition (CVD), composite materials manufacturing. In particular, mixed convection due to moving surfaces is very important in these applications. Mixed convection in a channel, as a result of buoyancy and motion of one of its walls has received little research attention and few guidelines are available for choosing the best performing channel configuration, particularly when radiative effects are significant. In this study a numerical investigation of the effect of radiation on mixed convection in air due to the interaction between a buoyancy flow and an unheated moving plate induced flow in a uniformly heated convergent vertical channel is carried out. The moving plate has a constant velocity and moves in the buoyancy force direction. The principal walls of the channel are heated at uniform heat flux. The numerical analysis is accomplished by means of the commercial code Fluent. The effects of the wall emissivity, the minimum channel spacing, the converging angle and the moving plate velocity are investigated and results in terms of air velocity and temperature fields inside the channel and wall temperature profiles, both of the moving and the heated plates, are given. Nusselt numbers, both accounting and not for the radiative contribution to heat removal, are also presented.

Numerical Study on Mixed Convection in Porous Media in a Channel With an Open Cavity Below

2010 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Paolo Mesolella ◽  
Sergio Nardini
Keyword(s):  
Mixed Convection ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Vertical Wall ◽  
Open Cavity ◽  
Temperature Fields ◽  
Forced Flow ◽  
Heated Wall ◽  
Local Thermal Equilibrium ◽  
Uniform Heat Flux

A numerical analysis of mixed convection in gas saturated metal foam in a horizontal channel with an open cavity heated at uniform heat flux on a vertical wall is studied numerically. Non-local thermal equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 PPI and ε = 0.909, the fluid is air and for the assisting case. Results, for different Peclet and Rayleigh numbers, are given in terms of solid and fluid wall temperatures and local Nusselt numbers and stream function and temperature fields. Results show that diffusive effect determined lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. The interaction between the forced flow in the channel and the buoyancy due to the heated wall determines different thermal and fluid dynamic behaviors.

Mixed Convection in Air in an Open Ended Cavity With a Moving Plate Parallel to the Cavity Open Surface

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Nicola Bianco ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Mixed Convection ◽  
Plate Motion ◽  
Uniform Heat Flux ◽  
Geometrical Parameters ◽  
Heated Plate ◽  
Open Surface ◽  
Moving Plate ◽  
Plate Temperature

In this study, a numerical investigation of mixed convection in air in an open ended cavity, with a moving plate parallel to the cavity open surface, is carried out. The moving plate has a constant velocity, whereas a vertical plate of the open cavity is heated at uniform heat flux. All the other walls are adiabatic. The numerical analysis is obtained by means of the commercial code FLUENT. Two configurations, assisting and opposing, are analyzed. In the assisting configuration, natural convection is supported by the plate motion, whereas, in the opposing configuration, natural convection and plate motion have opposing effects. The effect of different geometrical parameters, heat flux and moving plate velocity are analyzed. Results in terms of heated plate and moving plate temperature profiles are presented and simple monomial correlation equations for both the configurations are proposed between the terms Nu/Re0.6 and Ri.

Analysis of Mixed Convection in Vertical Convergent Channels

Volume 1 ◽  
2004 ◽  
Author(s):  
Nicola Bianco ◽  
Oronzio Manca ◽  
Alfonso W. Mauro ◽  
Vincenzo Naso
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Free Convection ◽  
Mixed Convection ◽  
Forced Flow ◽  
Uniform Heat Flux ◽  
Turbulent Model ◽  
Flat Plates ◽  
Convergent Channel ◽  
Converging Angle

Air mixed convection in a convergent channel with the two principal flat plates at uniform heat flux is analyzed numerically. In the considered system two parallel adiabatic extensions are placed downstream the convergent channel. The forced flow is obtained by imposing a pressure drop between the inlet and the outlet of the channel. The flow in the channel is assumed to be two-dimensional, turbulent and incompressible. A k-ε turbulent model is employed. Results in terms of dimensionless wall temperature distribution as a function of the walls converging angle, the Grashof number and the pressure drop are presented in the ranges: 0 ≤ ΔP ≤ 2.2·107, 2.8·104 ≤ Gr ≤ 2.1·105. Results show that increasing the angle of converging the Reynolds number increases at the same pressure drop. The larger the pressure drop the smaller the contribution of the free convection to the Reynolds number. Increasing the converging angle only slightly increases the ΔP value for which the effect of free convection is negligible.

Numerical Analysis of Opposing Mixed Convection in Air in a Vertical Channel With a Moving Plate

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Nicola Bianco ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Analysis ◽  
Mixed Convection ◽  
Vertical Channel ◽  
Forced Flow ◽  
Uniform Heat Flux ◽  
Transition Flow ◽  
Moving Plate ◽  
Buoyancy Flow

In this study a numerical investigation of mixed convection in air due to the interaction between a buoyancy flow and a moving plate induced flow in a vertical channel is carried out. The moving plate has a constant velocity and moves in the opposite direction with respect to the buoyancy force. The channel principal walls are heated at uniform heat flux. The numerical analysis is obtained by means of the commercial code Fluent. The effects of the channel spacing, heat transfer and moving plate velocity are investigated and results in terms of the channel wall and moving plate temperatures and Nusselt numbers are given. The wall temperature profiles allow to observe different behaviors of the flow motion inside the channel, a buoyancy flow, a forced flow and a transition flow related to the velocity of moving plate. The transition velocity increases as the heat flux and the channel gap increase. Dimensionless heat transfer results, Nu/Re0.68 as a function of Richardson number, Ri, present a good agreement with two correlations obtained for the buoyancy dominant flow, at Ri > 10, and forced dominant flow, at Ri < 10−3.

Numerical Study of Flow and Cooling Characteristics of Impinging Liquid Jets on a Moving Plate

2010 ◽  
Author(s):  
Sangil Son ◽  
Gihun Son ◽  
Ilseouk Park ◽  
Piljong Lee
Keyword(s):  
Level Set ◽  
Numerical Study ◽  
Jet Impingement ◽  
Temperature Fields ◽  
Liquid Jets ◽  
Moving Plate ◽  
Gas Phases ◽  
Steel Making ◽  
Single Jet ◽  
Interfacial Motion

Liquid jet impingement on a moving plate, which is applicable to cooling of hot plates in a steel-making process, is investigated numerically by solving the conservation equations of mass, momentum and energy in the liquid and gas phases. The free-surface or liquid-gas interface is tracked by an improved level-set method incorporating a sharp-interface technique for accurate imposition of stress and heat flux conditions on the liquid-gas interface. The level-set approach is combined with a non-equilibrium k-ε turbulence model. The computations are made for multiple jets as well as a single jet to investigate their flow and cooling characteristics. Also, the effects of moving velocity of plate, jet velocity and nozzle pitch on the interfacial motion and the associated flow and temperature fields are quantified.

MIXED CONVECTION IN AN INCLINED AND LID-DRIVEN RECTANGULAR ENCLOSURE HEATED AND COOLED ON ADJACENT WALLS

2008 ◽  
Vol 32 (2) ◽  
pp. 213-226 ◽  
Author(s):  
Elif Büyük Öğüt
Keyword(s):  
Mixed Convection ◽  
Differential Quadrature Method ◽  
Side Wall ◽  
Temperature Fields ◽  
Convection Flow ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Laminar Mixed Convection ◽  
Inclination Angles ◽  
Steady Laminar

Steady, laminar, mixed convection flow was considered in an inclined lid-driven rectangular enclosure heated from one side moving with a constant speed and cooled from the stationary adjacent side while the other sides are kept stationary and adiabatic. The governing equations were solved numerically for the stream function, vorticity, and temperature ratio using the differential quadrature method for various Reynolds, Grashof, and Richardson numbers as well as different aspect ratios and inclination angles for the enclosure. The results show that the motion of the side wall, the aspect ratio, and the inclination angle of the enclosure had significant effects on the flow and temperature fields.

scholarly journals Natural convection air flow in vertical upright-angled triangular cavities under realistic thermal boundary conditions

2016 ◽  
Vol 20 (5) ◽  
pp. 1407-1420 ◽  
Author(s):  
Jaime Sieres ◽  
Antonio Campo ◽  
José Martínez-Súarez
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Aperture Angle ◽  
Temperature Fields ◽  
Uniform Heat Flux ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Horizontal Wall ◽  
Rayleigh Numbers

This paper presents an analytical and numerical computation of laminar natural convection in a collection of vertical upright-angled triangular cavities filled with air. The vertical wall is heated with a uniform heat flux; the inclined wall is cooled with a uniform temperature; while the upper horizontal wall is assumed thermally insulated. The defining aperture angle ? is located at the lower vertex between the vertical and inclined walls. The finite element method is implemented to perform the computational analysis of the conservation equations for three aperture angles ? (= 15?, 30? and 45?) and height-based modified Rayleigh numbers ranging from a low Ra = 0 (pure conduction) to a high 109. Numerical results are reported for the velocity and temperature fields as well as the Nusselt numbers at the heated vertical wall. The numerical computations are also focused on the determination of the value of the maximum or critical temperature along the hot vertical wall and its dependence with the modified Rayleigh number and the aperture angle.

Approximate Analytical Solutions for Marangoni Mixed Convection Boundary Layer

2010 ◽  
Author(s):  
Yan Zhang ◽  
Liancun Zheng ◽  
Jiemin Liu
Keyword(s):  
Boundary Layer ◽  
Mixed Convection ◽  
Analytical Solutions ◽  
External Pressure ◽  
Immiscible Fluids ◽  
Temperature Fields ◽  
Convection Boundary Layer ◽  
Coupling Condition ◽  
Approximate Analytical Solutions ◽  
Convection Boundary

The paper deals with a steady coupled dissipative layer, called Marangoni mixed convection boundary layer, which can be formed along the interface of two immiscible fluids, in surface driven flows. The mixed convection boundary layer is generated besides the Marangoni convection effects induced flow over the surface due to an imposed temperature gradient, there are also buoyancy effects due to gravity and external pressure gradient effects. We shall use a model proposed by Chamkha wherein the Marangoni coupling condition has been included into the boundary conditions at the interface. The similarity equations are first determined, and the approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade´ approximant technique. The features of the flow and temperature fields as well as the interface velocity and heat transfer at the interface are discussed for some values of the governing parameters. The associated fluid mechanics was analyzed in detail.

Application of the Software System of Finite Element Analysis for the Simulation and Design Optimization of Solar Photovoltaic Thermal Modules

2020 ◽  
pp. 106-131 ◽  
Author(s):  
Vladimir Panchenko ◽  
Sergey Chirskiy ◽  
Valeriy Vladimirovich Kharchenko
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Solar Cells ◽  
Heat Removal ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Thermal Mode ◽  
Solar Photovoltaic ◽  
Element Analysis ◽  
Ansys System

The chapter discusses the simulation of thermal operating conditions and the optimization of the design of solar photovoltaic thermal modules. As a realization of the developed method, two photovoltaic thermal modules with one-sided solar cells with one-sided heat removal and two-sided solar cells with two-sided heat removal are presented. The components of the developed models of solar modules must be optimized on the basis of the required indicators of the thermal mode of operation of the modules. For this task, a method has been developed for visualizing thermal processes using the Ansys system of finite element analysis, which has been used to research thermal modes of operation and to optimize the design of the modules created. With the help of the developed method, the temperature fields of the module components, coolant velocity and its flow lines in the developed models of a planar photovoltaic thermal roofing panel and a concentrator photovoltaic thermal two-sided module are visualized.

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