Experimental and Numerical Investigation of the Heat Transfer Characteristics of Laminar Flow in a Vertical Circular Tube at Low Reynolds Numbers

An experimental study has been conducted to determine the heat transfer characteristics for low Reynolds number turbulent swirling LPG/Air flames impinging on a flat surface. Effect of variation of Reynolds number (3000–7000), dimensionless separation distance (H/d = 1 to 6) and equivalence ratio (φ = 0.8 to 2) on heat transfer characteristics has been determined at constant swirl number of 4. Further, experiments were also conducted to investigate the effect of swirl number on heat transfer characteristics at Re = 7000, φ = 1.0 and H/d = 5. It has been concluded that the major drawback of flame impingement i.e., non-uniformity in the heating can be resolved by using swirling flames in place of non-swirling flames. With increase in Reynolds number the flame becomes longer and broader. Also, at higher Re the flame becomes noisy and violent because of the enhanced turbulences in the flame. A dip in the temperature was observed at the stagnation point at all Re and this dip was more significant at higher Re. At small separation distances (H/d = 1 and 2) and at large Reynolds numbers (Re = 7000) heating is comparatively more non-uniform because of close proximity of the visible reaction zone to the plate resulting in intense heating in the stagnation region. High average heat fluxes were obtained at low separation distances and at larger Reynolds numbers.

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Flow and Convective Heat Transfer Characteristics of Nanofluids With Various Shapes of Alumina Nanoparticles

ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 1 ◽

10.1115/mnhmt2009-18173 ◽

2009 ◽

Cited By ~ 1

Author(s):

Kyo Sik Hwang ◽

Hyo Jun Ha ◽

Seung Hyun Lee ◽

Hyun Jin Kim ◽

Seok Pil Jang ◽

...

Keyword(s):

Heat Transfer ◽

Laminar Flow ◽

Convective Heat Transfer ◽

Flow Regime ◽

Convective Heat ◽

Circular Tube ◽

Al2o3 Nanoparticles ◽

Heat Transfer Characteristics ◽

Laminar Flow Regime ◽

Transfer Characteristics

This paper is to investigate flow and convective heat transfer characteristics of nanofluids with various shapes of Al2O3 nanoparticles flowing through a uniformly heated circular tube under fully developed laminar flow regime. For the purpose, Al2O3 nanofluids of 0.3 Vol.% with sphere, rod, platelet, blade and brick shapes are manufactured by a two-step method. Zeta potential as well as TEM image is experimentally obtained to examine suspension and dispersion characteristics of Al2O3 nanofluids with various shapes. To investigate flow characteristics, the pressure drop of Al2O3 nanofluids with various shapes are measured. In order to investigate convective heat transfer characteristics, the effective thermal conductivities of Al2O3 nanofluids with various shapes, the temperature distribution at the tube surface and the mean temperature of nanofluids at the inlet are measured, respectively. Based on the experimental results, the convective heat transfer coefficient of Al2O3 nanofluids with various shapes is compared with that of pure water and the thermal conductivity of Al2O3 nanofluids with various shapes. Thus, the effect of nanoparticles shape on the flow and convective heat transfer characteristics flowing through a uniformly heated circular tube under fully developed laminar flow regime is experimentally investigated.

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