ISSN Online: 2377-424X
ISBN Print: 0-89116-559-2
International Heat Transfer Conference 8
NUMERICAL STUDIES OF MIXED CONVECTION FLOWS IN THE ANNULUS BETWEEN VERTICAL CONCENTRIC CYLINDERS WITH ROTATING INNER CYLINDER
Abstrakt
A numerical study has been conducted to
determine the heat transfer characteristics and
flow patterns which develop around- a rotating,
heated vertical cylinder enclosed within a
stationary concentric cylinder. A tall annulus
(aspect ratio of 10) with fixed, adiabatic
horizontal endplates and a radius ratio of 2 has
been considered. Solutions reveal that two
instabilities exist for this geometry, one being
purely hydrodynamic and the other thermal in
origin. The hydrodynamic instability manifests
itself by the appearance of the toroidal Taylor
vortices, while the thermal instability is characterized by the sudden onset of a multicellular flow pattern. This paper investigates the mutual interaction of both modes of instability and the resultant effects on the flow patterns and heat transfer rates. A wide range of parameters is studied (0 ≤ Re ≤ 103; 0 ≤ Gr ≤ 105) for the air-filled gap (Pr = 0.7). Heat transfer rates are presented as a function of the rotational parameter σ = Gr/Re2. This parameter is a densiometric Froude number, and gives the relative importance of the buoyancy and rotational effects. Solutions are obtained by solving the time-dependent Navier-Stokes and energy equations, cast in the stream function -vorticity - swirl velocity form.