Whole field measurements to understand the effect of nanoparticle concentration on heat transfer rates in a differentially-heated fluid layer

This paper presents the results of an investigation concerned with measurements of the scale-size of the flow patterns near the so-called Malkus transitions. The flow patterns in a heated fluid layer were photographed at various Rayleigh numbers and these photographs subjected to quantitative analysis using an optical correlation computer. The results showed that the method provides a very sensitive technique for locating the transitions. Transitions reported by other investigators have been confirmed for Rayleigh numbers between 5.0 × 103 and 1.0 × 106, and an additional, previously unobserved, transition has been detected. Heat-transfer measurements were also made. This data demonstrated the limitations, compared to the optical method, of this approach to the detection of transitions.

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Effective Thermal Conductivity for Combined Radiation and Free Convection in an Optically Thick Heated Fluid Layer

Journal of Heat Transfer ◽

10.1115/1.3244403 ◽

1981 ◽

Vol 103 (1) ◽

pp. 114-120 ◽

Cited By ~ 5

Author(s):

M. Epstein ◽

F. B. Cheung ◽

T. C. Chawla ◽

G. M. Hauser

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Free Convection ◽

Effective Thermal Conductivity ◽

Radiative Heat ◽

Fluid Layer ◽

Convection Heat Transfer ◽

Turbulent Heat ◽

Free Convection Heat ◽

Heated Fluid

The effective thermal conductivity for radiative heat transfer within an optically thick fluid layer undergoing high Rayleigh number convection is derived. This result is combined with available “pure” free-convection heat-transfer correlations to obtain closed-form analytical descriptions of the gross properties of a radiating fluid layer heated internally or from below. These simple solutions compare favorably with recent work in which the governing energy equation incorporating both turbulent heat transport and thermal radiation is solved numerically.

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Natural convection induced by undulated surfaces in a porous enclosure filled with nanoliquid

Advances in Mechanical Engineering ◽

10.1177/1687814019875284 ◽

2019 ◽

Vol 11 (9) ◽

pp. 168781401987528 ◽

Cited By ~ 2

Author(s):

Abeer Alhashash ◽

Habibis Saleh

Keyword(s):

Heat Transfer ◽

Convective Flow ◽

Darcy Law ◽

Nanoparticle Concentration ◽

Governing Equations ◽

Transfer Rates ◽

Number Formula ◽

Water Base ◽

Porous Enclosure ◽

Effect Of Surface

Effect of surface undulation on convective flow in a porous enclosure is investigated in this present article. The porous enclosure is filled with a water-base nanoliquid containing Cu solid nanoparticles, and the porous layer is modeled using the Darcy law. The governing equations are solved numerically using the built-in finite element method of COMSOL. The investigation was carried out for several parameters: the nanoparticle concentration, [Formula: see text]; the amplitude of undulations, [Formula: see text]; the number of undulations, [Formula: see text]; and the Rayleigh number, [Formula: see text]. It is concluded that the strength of the nanoliquid circulation increases with increasing the amplitude or number undulations. It is found that the heat transfer rates were sensitive to the variation of undulation property, convection intensity, and nanoparticle concentration.

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