Energy Streamlines Analyses on Natural Convection Within Porous Square Enclosure With Internal Obstructions

Natural convection through a porous layer heated from the side with internal flow obstructions have been investigated based on visualization of total energy flow via energy streamfunctions or energy streamlines. Energy streamline has been introduced previously by Mahmud and Fraser (2007, “Visualizing Energy Flows Through Energy Streamlines and Pathlines,” Int. J. Heat Mass Transfer, 50, pp. 3990–4002) as an alternate convection heat transfer energy visualization technique. Energy streamlines consider all forms of related energy; for example, thermal energy, potential energy, kinetic energy, electrical energy, magnetic energy, and chemical energy. A finite volume method has been employed to solve momentum and energy balance as well as postprocessing energy streamfunctions. A parametric study has been carried out using the following parameters: Rayleigh number (Ra) from 10³ to 10⁶, Darcy number (Da) from 10⁻⁴ to 10⁻³, dimensionless thin fin lengths (L) 0.25, 0.5, and 0.75, dimensionless positions (H) 0.25, 0.5, and 0.75 with Prandtl number (Pr) 0.7. One finding of the present study is that, adding an obstruction in a cavity is similar to reducing Da of the porous medium. Therefore, the average Nusselt number calculated on the hot wall of the cavity always degraded compared to the no obstruction case whenever a baffle is attached. Thus the attached horizontal obstruction adds some thermal insulation effect. This finding is important in double wall space filled with fiberglass insulation in contemporary buildings, where the side wall is reinforced on the inside with structural members.