Natural convection in a hemispherical enclosure heated from below

Shiina, Yasuaki; Fujimura, Kaoru; Kunugi, Tomoaki; Akino, Norio

doi:10.1016/0017-9310(94)90176-7

Cited by 52 publications

(21 citation statements)

References 25 publications

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“…The natural convective heat transfer coefficient is then calculated by means of correlations of the Nusselt–Rayleigh type. The same applies to the hemispherical enclosure considered by Shiina et al (1994) containing a fluid with a Prandtl number ranging between 6 and 13,000. Some applications are treated by Baïri (2014a) and Baïri et al (2015) using air as convective fluid and considering various thermal boundary conditions compatible with the intended applications.…”

Section: Introductionmentioning

confidence: 99%

Natural convective cooling of electronics contained in tilted hemispherical enclosure filled with a porous medium saturated by water-copper nanofluid

Baı̈ri

Bauzin

Martín-Garín

et al. 2019

HFF

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Purpose The purpose of this study is to determine the thermal behavior of a hemispherical electronic device contained in a concentric hemispherical enclosure, cooled by means of free convection through a porous medium saturated with a water–copper nanofluid. Influence of various parameters on the thermal state of this device is processed in this work. The high power generated by the dome leads to a Rayleigh number varying in the 5.2 × 107-7.29 × 1010 range. The volume fraction of the monophasic nanofluid varies between 0 (pure water) and 10 per cent while the base of the hemispherical cavity (disc) is inclined between 0° (horizontal disc with dome facing upward) and 180° (horizontal disc with dome facing downward). Design/methodology/approach The three-dimensional numerical approach is carried out by means of the volume control method associated to the SIMPLE algorithm. Findings The work shows that the average temperature of the active component increases with the Rayleigh number according to a conventional law of the power type. The increase in the angle of inclination also goes with a systematic rise in the average temperature. However, increasing the ratio of the solid–fluid thermal conductivities decreases the average temperature of the component, given the respective contributions of the conductive and natural convective phenomena occurring through the nanofluid saturated porous media. The values of this ratio vary in this work between 0 (interstice between the two hemispheres without porous medium) and 70. Originality/value The correlation proposed in this work allows to calculate the temperature of the active electronic component for all the combinations of the four influence parameters which vary in wide ranges.

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Section: Introductionmentioning

confidence: 99%

Natural convective cooling of electronics contained in tilted hemispherical enclosure filled with a porous medium saturated by water-copper nanofluid

Baı̈ri

Bauzin

Martín-Garín

et al. 2019

HFF

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“…They are relatively high, varying between 3.55 × 10 9 and 5.60 × 10 11 for horizontal and vertical cavities, respectively. The value 3.55 × 10 9 corresponding to α ¼ 0°i s greater than that given by Shiina et al (1994), equal to 1 × 10 9 . However, it Figure 4.…”

Section: (A) Exponent N(α)mentioning

confidence: 72%

“…Nu-Ra correlations should be noted that the thermal boundary conditions treated in both studies are different since in the work by Shiina et al (1994), a constant temperature is imposed on the base of the hemisphere and hence the Rayleigh number is calculated differently. In addition, the thermophysical properties of the air are not evaluated at the same temperature, which causes a difference in the resulting Rayleigh number.…”

mentioning

confidence: 99%

Nu-Ra correlations for natural convection at high Ra numbers in air-filled tilted hemispherical cavities with dome oriented upwards. Disk submitted to constant heat flux

Baı̈ri¹,

María

Alilat³

et al. 2015

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose -The purpose of this paper is to propose correlations between Nusselt and Rayleigh numbers for the case of inclined and closed air-filled hemispherical cavities. The disk of such cavities is subjected to a constant heat flux. The study covers a wide range of Rayleigh numbers from 5 × 10 7 to 2.55 × 10 12 . Design/methodology/approach -Correlations are obtained from numerical approach validated by experimental measurements on some configurations, valid for several angles of inclination of the cavity between 0°(horizontal disk) and 90°(vertical disk) in steps of 15°. Findings -The statistical analysis of a large number of calculations leads to reliable results covering laminar, transitional and turbulent natural convection heat transfer zones. Practical implications -The proposed correlations provide solutions for applications in several fields of engineering such as solar energy, aerospace, building, safety and security. Originality/value -The new relations proposed are the first published for high Rayleigh numbers for this type of geometry. They supplement the knowledge of natural convection in hemispherical inclined cavities and constitute a useful tool for application in various engineering areas as solar energy (thermal collector, still, pyranometer, albedometer, pyrgeometer), aerospace (embarked electronics), building, safety and security (controlling and recording sensors). Nomenclature a thermal diffusivity of the air (m 2 s −1 ) C p specific heat at constant pressure ( J kg −1 K −1 ) g acceleration due to the gravity (m s −2 ) k(α) coefficient of the correlations Nu a ¼ kðaÞRa nðaÞ (-) n(α) exponent of Ra φ in the correlations Nu a ¼ kðaÞRa nðaÞ (-)

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“…The numerical procedure was validated using the experimental work reported by Yasuaki et al [43] as shown in table 2. The enclosed hemisphere was experimentally studied under steady state, laminar conditions.…”

Section: Validationmentioning

confidence: 99%

Numerical modelling and optimisation of natural convection heat loss suppression in a solar cavity receiver with plate fins

2015

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This study details the numerical modeling and optimization of natural convection heat suppression in a solar cavity receiver with plate fins. The use of plate fins attached to the inner aperture surface is presented as a possible low cost means of suppressing natural convection heat loss in a cavity receiver. In the first part of the study a three-dimensional numerical model that captures the heat transfer and flow processes in the cavity receiver is analyzed, and the possibilities of optimization were then established. The model is laminar in the range of Raleigh number, inclination angle, plate height and thickness considered. In the second part of the study, the geometric parameters considered were optimized using optimization program with search algorithm. The results indicate that significant reduction on the natural convection heat loss can be achieved from cavity receivers by using plate fins, and an optimal plate fins configuration exit for minimal natural convection heat loss for a given range of Raleigh number. Reduction of up to a maximum of 20% at 0 o receiver inclination was observed. The results obtained provide a novel approach for improving design of cavity receiver for optimal performance.

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Natural convection in a hemispherical enclosure heated from below

Cited by 52 publications

References 25 publications

Natural convective cooling of electronics contained in tilted hemispherical enclosure filled with a porous medium saturated by water-copper nanofluid

Natural convective cooling of electronics contained in tilted hemispherical enclosure filled with a porous medium saturated by water-copper nanofluid

Nu-Ra correlations for natural convection at high Ra numbers in air-filled tilted hemispherical cavities with dome oriented upwards. Disk submitted to constant heat flux

Numerical modelling and optimisation of natural convection heat loss suppression in a solar cavity receiver with plate fins

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