A TRANSIENT NATURAL-CONVECTION IN AN ANNULAR ENCLOSURE

Abstract

A transient natural convection in an annular enclosure is investigated numerically. The upper and lower walls are adiabatic, the outer wall is maintained at a low temperature and the temperature of the inner wall is changed to a high value abruptly. During the computing process, the numerical method of SIMPLE-R with power law scheme is adopted to solve the axially-symmetric governing equations of the continuity, momentum and energy. The Rayleigh number of 10(4) and 10(6) are considered, respectively. Since the area of the annular cross section enlarges with the increasing of the radius, the phenomena occurring in the annular enclosure are different from those occurring in the rectangular enclosure. In addition, the results show that in the initial region the variations of the total Nusselt of the inner wall rebounds under Rayleigh number of 10(6) case and does not fluctuate under Rayleigh number of 10(4) case, which are similar to those of the rectangular enclosure.