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A numerical study is presented for a mixed convection in a two-dimensional partially open rectangular cavity. The uniform heat-flux, discrete heat sources are flush-mounted on three identical heat conducting vertical boards, which are mounted on the bottom wall of a partially open cavity. An external airflow enters the cavity through an opening (inlet) in the left vertical wall and exits from the opposite opening (outlet) in the right vertical wall. In this paper, the effect of the number of boards on the flow and thermal field characteristics are investigated and compared with a single board case, where appropriate. The simulations are carried out for wide ranges of Reynolds number and Richardson number (buoyancy parameter, Ri = Gr/Re2 ) for a working fluid of air (Pr = 0.71). The solutions were found to be time-independent for only sufficiently low values of Re and Ri. For large Re and/or Ri, the oscillatory flow is analyzed by considering time-histories, frequencies and instantaneous snapshots for the field variables. The effect of the oscillatory flow on the heat removal from the heat source is discussed. It was observed that with the onset of oscillatory flow, the re-circulating cells set into motion and thus considerable reduction in the maximum dimensionless temperature is achieved, making the cooling with convection as an effective mode of heat transfer. The results also indicate that the Reynolds number and Richardson number have a strong effect on the temperature and velocity distributions as well as the average Nusselt number evaluated over the heat source.Copyright © 2009 by ASME |
