Mixed Convection Study in a Ventilated Square Cavity with a Heat Source Cooled by Nanofluids
Paulo Mohallem Guimarães1; Renato José Pinto2; Genésio José Menon3
1 Universidade Federal de Itajubá - Campus Itabira; 2 Universidade Federal de Itajubá; 3 Universidade Federal de Itajubá-Campus Itajubá
doi:10.20906/CPS/COB-2015-1690
Resumo
This work aims to study the heat transfer by mixed convection in a square cavity with openings on its vertical walls through which nanofluid flows. The nanofluid is composed of Copper nanoparticles and water as its base-fluid. At the inlet, the velocity and temperature profiles are given. A numerical study is carried out by using a code developed by the authors. Finite element method is used. The regime is laminar and non-steady, although some results are shown only when it reaches the steady-state. A mesh independency study is also performed in order to find an appropriate mesh that may give a error, that is, less than 1%, when analyzing the Nusselt number and the maximum temperature on the heat source. Some parameters are varied as follows: Reynolds number from 50 to 500, nanofluid concentration from 0 (pure water) to 1%, and the Grashof number from 1000 to 100000. Some results are given as follows. The direction of the inlet towards the outlet flow is in favor of and against buoyancy forces, that is, upwards and downwards direction of the primary flow. Although the forced flow is present in the ascending direction, this work presents an interesting result when the Reynolds number is increased by keeping the Grashof number constant. One should expect from this that heat transfer should increase with Reynolds going up. Nevertheless, the opposite happens. This occurs due to a series of combined factors: the geometry and also the velocities involved. As Re is increased, so is the strength and size of the recirculation around the heat source and therefore impairing colder fluid to reach the heat source. The fluid is stuck around the heated source because it does not have strength enough to break the high pressure region caused by the primary flow due to forced velocities towards the exit. In general, when ascending cases are regarded, the nanoparticle concentration effect of heat transfer enhancement is of the order of 4% for both cases, that is, concentrations of 0 (pure water) and 1%. The authors strongly recom
Palavras-chave: Nanofluid; Ventilated Cavity; Mixed Convection