THE ROLE OF NATURAL CONVECTION DURING MELTING AND SOLIDIFICATION OF PCM IN A VERTICAL CYLINDER

Measurements of heat transfer during melting and solidfkation of n-eicosane and rt-hexadecane were performed in vertical cylinders with two different lengths and diameters. Radial temperature distibutions were measured with lime at different heights in all the tests. To evaluate the rate of heat charged and discharged from the cylinder at different heights, the data were recorded and processed directly usinj; on-line computer. A theoretical model was developed based on solving the one-dimensional unsteady heat conduction equation in both phases. Convection in the liquid was included using an effective thermal conductivity; a lumped parameter that includes also the effect of the two-dimensional heat transfer during melting. The model, which may be used for the prediction of both melting and solidfkation experiments, takes into account the effect of initial subcooling or superheating and includes the heat capacity of the cylinder containing the PCM. The agreement of the model was good not only with the experimental results of this work, but also with the published work of the others.