Papers Published

  1. Vargas, J.V.C. and Bejan, A., Optimization principle for natural convection pulsating heating, Journal of Heat Transfer, Transactions ASME, vol. 117 no. 4 (1995), pp. 942 - 947 .
    (last updated on 2007/04/06)

    This is a theoretical, numerical, and experimental study of natural convection heat transfer from an immersed surface with intermittent uniform heat flux. Scale analysis predicts that the `on' time interval can be optimized such that the overall Nusselt number is maximized. Furthermore, Nu increases monotonically as the `off' time interval decreases. These features are verified and determined more accurately by complete numerical simulations for a vertical flat surface in the range 103 <= Ra <= 105 and Pr = 7, where Ra is based on heat flux and wall height. They are further verified by means of water experiments in the range 1010 <= Ra 1011. The pulsating heater configurations tested experimentally are the vertical cylinder, which approximates boundary layer flow on a plane surface, and the horizontal cylinder. The optimal square-wave heat pulse for a natural convection immersion heater is reported in general (scaling correct) terms.

    Heat transfer;Numerical methods;Simulation;Optimization;Heat flux;Heating;