Numerical studies of natural convection phenomena for a vertical cylinder with multiple lateral baffles in triangular and hexagonal enclosures

Abstract

Numerical case studies for natural convection were conducted for triangular and hexagonal enclosures as a follow-up to a previous study of natural convection for a baffled cylinder in a square enclosure. For a Prandtl number of 0.71, a range of the length ratio corresponding to the spatial ratio was varied from 0.4 to 0.9, and Rayleigh numbers from 2.5 × 103 to 5.0 × 107 was considered. To model the buoyancy force, the Boussinesq approximation was adopted. The boundary condition of constant wall temperature was applied to the cylinder and enclosure surfaces. Overall trends of the heat transfer performance were separated into conduction- and convection-dominated regimes, similar to the previous study. Because of the wider space of the triangular enclosure, however, an advantage of the convection effect was observed in the triangular enclosure. Due to the short distance between the cylinder and enclosure, the hexagonal enclosure had a more conduction-dominated characteristic than that of the triangular enclosure. A strong correlation was identified between the location of the high-energy vortex and the Nusselt number distribution. Using the calculation results, an improved average Nusselt number correlation is proposed to include triangular, square and hexagonal enclosures.

Keywords

• Natural convection
• Polygonal enclosure
• Planar shape battery
• Sodium β”-alumina battery