Abstract
This work investigates the characteristics and performance of natural convection from locally heated horizontal rectangular plate-fin heat sinks using 3-D unsteady numerical analysis. Different fin lengths (L = 128 or 254 mm), fin heights (H = 38 or 45 mm), heat fluxes (q = 0.9 or 1.8 W/cm ), and heater positions (symmetric or asymmetric heating) are examined. For these long heat sinks, oscillating sliding-chimney plume always prevails to yield oscillating heat transfer coefficients. For each case, the time-averaged overall heat transfer coefficient h and the averaged base plate temperature T are calculated. The T is then used as the input uniform temperature to obtain the equivalent time-averaged overall heat transfer coefficient h for all the investigated cases, h differs from h by less than 4%. This means that h for a locally heated condition may be equivalently obtained employing empirical Nu correlations derived for uniform-temperature horizontal heat sinks, as long as the average base temperature T is used