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Printed on Recycled Paper Experimental Transient Natural Convection in Enclosures

The transient heat transfer response is examined for a heat source within a fluidfilled enclosure. The specific geometry studied is a toroid centered within a cylinder filled with water. This geometry has application to in-tank heat exchangers common in many thermal storage strategies. The initial condition is an isothermal, quiescent fluid with a step change in coil wall temperature. The transient heat transfer response can be divided into three regimes: pure conduction, quasi-steady, and decay. The transient heat transfer was studied experimentally by pumping heated fluid through the toroid. Bulk temperature of the enclosure was measured, as was the temperature of the heated cylinder. The experimental response compares well to the previous numerical study done of this geometry. The duration of both the conduction period and the quasisteady period compared very well to the numerical study. The effect of coil height within the enclosure was studied for height ratio values (R) of 0.7, 0.4, 0.3, 0.2, 0.1, and 0.029. It was found that an R value of 0.029 produced the best heat transfer in that it heated the enclosure fluid most quickly.