Effect of Position of a Square-Shaped Heat Source on the Buoyancy-Driven Heat Transfer in a Square Cavity Filled with Nanofluid

Buoyancy-driven heat transfer due to a square-shaped heater placed inside a square cavity filled with the TiO2-water nanofluid is investigated numerically. The heater is maintained at a constant temperature Th while the cavity walls are kept at a lower constant temperature Tc. The governing equations are solved using the finite volume method and the SIMPLER algorithm. The simulations are performed for six different positions of the heat source inside the cavity, a range of Rayleigh numbers from 103 to 106, and different volume fractions of the nanoparticles. The ratio of the height (width) of the heat source to that of the cavity is taken as 0.2. The results shows that the fluid flow and heat transfer characteristics inside the cavity strongly depend on the location of the heat source. For Ra = 103, i.e., conduction-dominated heat transfer regime, maximum heat transfer rate is achieved by placing the heat source close to the corners of the cavity; while, for Ra = 106, positioning the heat source near the middle of the cavity''s bottom wall yields the maximum average Nusselt number. Moreover, it is observed that the average Nusselt number is generally an increasing function of the volume fraction of the nanoparticles.