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Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero PowerPoint Presentation
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Turbulent Thermal Convection inside Enclosures by Direct Numerical Simulation and Nonlinear Analysis. Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero. Scheme. Why study thermal convection inside enclosures? Objectives Natural (free) convection

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Turbulent Thermal Convection inside Enclosures by Direct Numerical Simulationand Nonlinear Analysis

Alfredo José Rodríguez Alarcón

Advisors:

Dr. Francesc Giralt

Dr. Joan Herrero

scheme
Scheme
  • Why study thermal convection inside enclosures?
  • Objectives
  • Natural (free) convection
  • Two dimensional convective heat transfer inside enclosures
  • Remarks
  • Project emphasis and summary

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

thermal convection inside enclosures

T2

T1>T2

g

Fluid

T1

Thermal convection insideenclosures

Problemconfiguration

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

why study thermal convection inside enclosures
Why study thermal convection inside enclosures?

Compact Vacuum Furnace

  • This configuration is often employed for the reduction of energy loss, e.g.
    • Thermal insulation of furnaces and similar systems.
    • Solar energy collectors.

Sketch of a flat-plate collector

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

why study thermal convection inside enclosures1
Why study thermal convection inside enclosures?
  • In manufacturing systems, flow regimes determination is important because product quality can be affected by the flow patterns, e. g.
    • Crystal growing facilities
    • Melting furnaces
    • Plastic molding systems

Vertical velocity contours in the horizontal midplane z=0 for different flow patterns (Puigjaner et al. 2004)

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

why study free convection inside enclosures heated from below
Why study free convection insideenclosures heated from below?
  • Theoretical developments and understanding of the convective heat transfer phenomena.

“Convection is a major feature of the dynamics of the oceans, the atmosphere, and the interior of stars and planets.” (Bodenschatz et al. 2000)

Temperature isosurface for the nondimensional value of T=0.6

Pr=100. (Breuer et al. 2004)

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

objectives
Objectives

Overall

  • To carry out a primary study on turbulent thermal convection inside cubical enclosures by direct numerical simulation and nonlinear analysis.

Secondary

  • To develop an adequate computational code for the study of turbulent thermal convection inside cubical enclosures.

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

natural thermal convection
Natural (thermal) convection
  • The two basic Heat Transfer processes are conduction and radiation.
  • Conduction is due to the motion of microscopic particles that comprise a material.
  • Convection occurs when conductive heat transfer is coupled with the motion of the fluid.
  • In general, in the natural convection fluid movement is due to density differences in presence of a body field (i.e. gravitational acceleration).

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

two dimensional convective heat transfer inside enclosures

Quiescent, thermally stratified fluid

T1>T2

T2

H

g

g

T1

RaH < 1708

NuH = 1

Two dimensional convective heat transfer inside enclosures

Cellular flow pattern

T1>T2

T2

H

T1

RaH > 1708

NuH > 1

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

two dimensional convective heat transfer inside enclosures1
Two dimensional convective heat transfer inside enclosures
  • Rayleigh number (RaH), Nusselt number (NuH) as well as Prandlt number (Pr) appear in scale analysis and dimensionless equations.
  • When governing equations are written in dimensionless disturbance variables, the RaH determines the emerging of flow instabilities.

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

remarks
Remarks
  • The initial flow is laminar and with increasing Ra, it undergoes transition to turbulence.
  • NuH, is function of RaH, Pr, geometry, thermal boundary conditions, flow structures.

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

remarks1
Remarks
  • Currently, turbulent thermal convection has been better studied through experiments, hence there are not enough 3D numerical simulations.
  • Transition to turbulence and turbulence itself need further understanding due to the difficulty of characterizing both numerically as well as experimentally chaotic fluid movement.

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

project emphasis
Project emphasis
  • To understand the physics of thermal convection inside enclosures.
  • To be aware of the advantages and limitations of current numerical methods available for the problem of study.
  • Select the appropriate numerical scheme to develop computational code in FORTRAM.
  • Test code developed with known problems and previous analysis.

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

questions comments
Questions, comments?

Thank you

Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.