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)

   Abstract:
   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.

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