Research Papers

Eddie Leonardi Memorial Lecture: “Natural Convection From Earth to Space”

[+] Author and Article Information
Victoria Timchenko

 School of Mechanical and Manufacturing Engineering, UNSW, Sydney, 2052 Australiav.timchenko@unsw.edu.au

Matériel pour l’Etude des Phenomènes Intérrasants de la Solidification sur Terre et en Orbite.

J. Heat Transfer 134(3), 031014 (Jan 18, 2012) (14 pages) doi:10.1115/1.4005149 History: Received August 21, 2010; Revised June 06, 2011; Published January 18, 2012; Online January 18, 2012

This lecture is dedicated to the memory of Professor Eddie Leonardi, formerly International Heat Transfer Conference (IHTC-13) Secretary, who tragically died at an early age on December 14, 2008. Eddie Leonardi had a large range of research interests: he worked in both computational fluid dynamics/heat transfer and refrigeration and air-conditioning for over 25 years. However starting from his Ph.D. ‘A numerical study of the effects of fluid properties on natural convection’ awarded in 1984, one of his main passions has been natural convection and therefore the focus of this lecture will be on what Eddie Leonardi has achieved in numerical and experimental investigations of laminar natural convective flows. A number of examples will be presented which illustrate important difficulties of numerical calculations and experimental comparisons. Eddie Leonardi demonstrated that variable properties have important effects and significant differences occur when different fluids are used, so that dimensionless formulation is not appropriate when dealing with flows of fluids with significant changes in transport properties. Difficulties in comparing numerical solutions with either numerically generated data or experimental results will be discussed with reference to two-dimensional natural convection and three-dimensional Rayleigh–Bénard convection. For a number of years Eddie Leonardi was involved in a joint US-French-Australian research program—the MEPHISTO experiment on crystal growth—and studied the effects of convection on solidification and melting under microgravity conditions. Some results of this research will be described. Finally, some results of experimental and numerical studies of natural convection for building integrated photovoltaic (BIPV) applications in which Eddie Leonardi had been working in the last few years will be also presented.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 2

Streamlines (a), (c), (e) and isotherms (b), (d), (f) for a square cavity, Ra = 105, ɛ  = 1 indicating the effect of the progressive introduction of variable properties. (a) and (b): dashed lines—BA, solid lines—variable density only; (c) and (d): dashed lines—variable density only, solid lines—variable density and viscosity; (e) and (f): dashed lines—variable density and viscosity, solid lines—variable density, viscosity, and conductivity.

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Figure 14

Nondimensional vertical velocity as a function of position on a horizontal line parallel to the x-axis passing through the centre of the enclosure (Fig. 1). Circles—measured values, solid curves—calculated values: W = 90%, T'c  = 16.3 °C, T'h  = 43 °C, T'∞  = 23 °C, r = 6, Ram  = 14,300, Pr = 900.

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Figure 15

Nondimensional isotherms—Numerical results: (a) top of bottom glass cover (hot) and (b) bottom of top glass divider (cold)

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Figure 16

Isovel distribution of the nondimensional vertical velocity on the horizontal midplane with various materials used on the side wall of the enclosure (a) case (I) insulating material; (b) case (II) material with half the conductivity of Perspex; and (c) case (III) Perspex

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Figure 17

Isotherms on vertical planes parallel to the short side of the enclosure: Isotherms on vertical planes parallel to the short side of the enclosure. case (I); plane through the centre of the ascending region of the second square in Fig. 1. case (III); plane through the centre of the ascending edge of the third roll Fig. 1.

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Figure 18

Solid solute concentration (a) along the ampoule centre line and (b) across the ampoule

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Figure 19

Interface shape

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Figure 20

Heating configuration modes

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Figure 21

Average Nusselt Number Nud as a function of Rayleigh number Rad*=: (a) C1, heating configuration and (b) C2, heating configuration

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Figure 22

Temperature fields along the two walls, S1 and S2, for a/H = 1/15, solid lines correspond to numerical simulations and (▪) symbols correspond to experiment

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Figure 1

Density as a function of temperature at a pressure of 101 kPa: (a) Air and (b) water

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Figure 3

Comparison of flow fields calculated with and without the BA for Ra = 104 . Water.

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Figure 4

Comparison of flow fields calculated with and without the BA. Air.

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Figure 5

Comparison of flow fields calculated with and without the BA. Water.

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Figure 6

Comparison of temperature fields calculated with and without the BA. Air.

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Figure 7

Comparison of temperature fields calculated with and without the BA. Water.

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Figure 8

Corner pressure, po , as a function of Rayleigh number, Ra, for various values of ɛ: ɛ  = 0.01 (x); ɛ  = 0.1 (○); ɛ  = 0.5 (Δ); ɛ  = 1 (∇); ɛ  = 2 (□). Dashed lines represent the values calculated from Eq. 6.

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Figure 9

Comparison of shift in the cell centre with hot wall on the left and cold wall on the right: (a) Flow visualization from Morrison and Tran [24]; (b) Variable property solution with adiabatic end walls; (c) Variable property solution with heat loss through the end walls. Ra = 5.9 × 104, T'h-T'c  = 10 °C, T'r=T'c  = 303 K, L = 5.

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Figure 10

Variation in the dynamic viscosity of three possible fluids

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Figure 11

Horizontal nondimensional velocity, w, as a function of height, y, for pure glycerol, linear and inverse fluids. Ram  = 11,000 and r = 15

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Figure 12

Schematic diagram of cavity (a) Front (z) view and (b) Side (x) view

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Figure 13

Experimental flow patterns on horizontal midplane: T'c=16.3 ∘C, T'h=47 ∘C, T'h=13 ∘C, T'∞=23 ∘C, W = 90% (r = 6, Ram  = 14,300)




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