Heat and fluid flow resulting from the chimney effect in a symmetrically heated vertical channel with adiabatic extensions

An experimental study on a channel-chimney system was carried out in order to elucidate the behavior of heat transfer and fluid flow. The results are presented in terms of local air temperature measurements inside the symmetrically heated channel and between the adiabatic extensions. Different fluid motion regions are observed inside the chimney. Inflows of air are detected in the lower extension ratio, particularly for large values of the ratio of the width of chimney to that of the heated channel. Some typical configurations show the presence of a vortex structure for an expansion ratio greater than one close to the corner regions in the chimney. Some monomial correlation equations between the local Nusselt number, the channel Rayleigh number and the geometric parameters are proposed. The dimensionless parameters are in the following ranges: 10(2) less than or equal to Ra* (B/b) less than or equal to 10(6); 1.5 less than or equal to L/L-h less than or equal to 4.0; 1.0 less than or equal to B/b less than or equal to 4.0, in which L is the total height of the system, L-h is the height of the heated channel, B is the width of the chimney and b is the width of the heated channel. A good agreement between the correlation and the experimental data is observed. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.