The laminar mixed convection in a vertical annular duct is studied. The fully developed region is considered under the hypothesis of parallel flow. The momentum local-balance equation and the energy local-balance equation are solved analytically by means of the Fourier-series expansions method. Moreover, the Fanning friction factors are determined. Two particular cases are considered: an annular duct with the inner wall adiabatic and the outer wall subjected to a sinusoidal heat-flux distribution in the angular direction; an annulus with the inner wall subjected to a sinusoidal heat-flux distribution and the outer wall adiabatic. The threshold value of the ratio Gr/Re for the onset of the phenomenon of flow reversal is determined as a function of the duct aspect ratio. Finally, the solution for a more general case is determined: the annular duct has both walls subjected to arbitrary heat-flux distributions, which can be described as Fourier sine series with respect to the angular coordinate.
Titolo: | Convection in a vertical annular duct with circumferentially variable boundary conditions. |
Autore/i: | BARLETTA, ANTONIO; LAZZARI, STEFANO; ZANCHINI, ENZO |
Autore/i Unibo: | |
Anno: | 2004 |
Rivista: | |
Digital Object Identifier (DOI): | http://dx.doi.org/10.2514/1.4293 |
Abstract: | The laminar mixed convection in a vertical annular duct is studied. The fully developed region is considered under the hypothesis of parallel flow. The momentum local-balance equation and the energy local-balance equation are solved analytically by means of the Fourier-series expansions method. Moreover, the Fanning friction factors are determined. Two particular cases are considered: an annular duct with the inner wall adiabatic and the outer wall subjected to a sinusoidal heat-flux distribution in the angular direction; an annulus with the inner wall subjected to a sinusoidal heat-flux distribution and the outer wall adiabatic. The threshold value of the ratio Gr/Re for the onset of the phenomenon of flow reversal is determined as a function of the duct aspect ratio. Finally, the solution for a more general case is determined: the annular duct has both walls subjected to arbitrary heat-flux distributions, which can be described as Fourier sine series with respect to the angular coordinate. |
Data prodotto definitivo in UGOV: | 2005-09-20 12:00:46 |
Appare nelle tipologie: | 1.01 Articolo in rivista |