Entransy dissipation minimization for liquid-solid phase change processes

Abstract

The liquid-solid phase change process of a simple one-dimensional slab is studied in this paper. By taking entransy dissipation minimization as optimization objective, the optimal external reservoir temperature profiles are derived by using optimal control theory under the condition of a fixed freezing or melting time. The entransy dissipation corresponding to the optimal heat exchange strategies of minimum entransy dissipation is 8/9 of that corresponding to constant reservoir temperature operations, which is independent of all system parameters. The obtained results for entransy dissipation minimization are also compared with those obtained for the optimal heat exchange strategies of minimum entropy generation and constant reservoir temperature operations by numerical examples. The obtained results can provide some theoretical guidelines for the choice of optimal cooling or heating strategy in practical liquid-solid phase change processes.