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.

### Convection in a vertical annular duct with circumferentially variable boundary conditions

#### 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.
##### Scheda breve Scheda completa Scheda completa (DC)
2004
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: `https://hdl.handle.net/11567/935146`
• ND
• 1
• 1