Author(s)

A. Andreozzi, B. Buonomo & O. Manca

Abstract

A numerical investigation on two-dimensional transient natural convection in a vertical channel-chimney system with the channel heated asymmetrically and the chimney geometrically asymmetric is carried out. The heated channel wall is at uniform heat flux and the other one is assumed to be adiabatic. The chimney walls are adiabatic. Results are obtained for different expansion and extension ratios of the channel-chimney system and Rayleigh number equal to 104 and 106. They are presented in terms of maximum heated wall temperatures and average Nusselt number as a function of time and stream function fields for some time values. Optimal thermal configurations in terms of minimum value of maximum heated wall temperature and maximum average Nusselt numbers are evaluated. Complex flow structures in the channel-chimney system are detected. Keywords: natural convection, numerical investigation, asymmetric channelchimney systems. 1 Introduction More recent trends in natural convection research are to find new configurations to improve the heat transfer parameters or to analyze standard configurations to carry out optimal geometrical parameters for a higher heat transfer rate and the transient behavior for a suitable thermal design. A very simple method, which allows to improve the chimney effect and consequently heat transfer rate in vertical channels and other configurations, is to place parallel adiabatic extensions downstream heated configurations [1, 2]. A first research on the chimney effects was obtained by Haaland and Sparrow [2]. A vertical channel with point source or distributed heat source situated at

Keywords

natural convection, numerical investigation, asymmetric channelchimney systems.