Buoyancy-Induced Heat Transfer in a Trapezoidal Enclosure with Offset Baffles

Abstract

A numerical study has been conducted to examine the effects on heat transfer of mounting two offset baffles onto the upper inclined and lower horizontal surfaces of trapezoidal cavities. Two thermal boundary conditions are considered. In the first, the short left vertical wall is heated while the long right vertical wall is cooled (buoyancy-assisting mode along the upper inclined surface of the cavity). In the second, the long right vertical wall is heated while the short left vertical wall is cooled (buoyancy-opposing mode along the upper inclined surface of the cavity). For both boundary conditions, computations are performed for several offset baffle heights, four Rayleigh number (Ra) values, three Prandtl number (Pr) values, and two baffle positions (Position I and Position II). In Position I, the lower baffle is offset toward the short vertical wall and the upper baffle is offset toward the long vertical wall of the enclosure, whereas in Position II, the lower and upper baffles are offset toward the long and short vertical walls, respectively. Results reveal a decrease in heat transfer in the presence of baffles, with the rate generally increasing with increased baffle height and Pr. At a given baffle height and Ra, Nussett number (Nu) values are lower in the buoyancy-opposing mode. For both boundary conditions, the highest decrease is achieved in fully partitioned enclosures.