Numerical analysis of melting in rectangular enclosures heated uniformly or discretely by the conducting side walls.

A numerical study has been conducted for natural convection dominated melting inside uniformly and discretely heated rectangular cavities. A computational methodology based on the enthalpy method for the phase change is first presented and validated with experimental data. The model is next employed to determine the effect of the source dimensions beta and span eta, of the aspect ratio of the cavity A and of the wall-PCM thermal diffusivity <(alpha)over bar> ratio on the melting process. Results show the benefits of using discrete heat sources instead of a uniformly heated wall. For high aspect ratio enclosures (A greater than or similar to 4), configurations leading to well controlled source temperatures and relatively long melting times have been obtained. For cavities of aspect ratio A less than or similar to 4.0, the source span eta is the most influential parameter. If eta less than or similar to 0.45, the melting times are shorter and the temperatures of the sources remain equal and moderate during the melting process. Threshold values <(alpha)over bar>(min) above which melting becomes independent of the source distribution were determined for cavities of various aspect ratios. (C) Elsevier, Paris.