Determination of unsteady container temperatures during freezing of three-dimensional organs with constrained thermal stresses

摘要

A fully automatic procedure for maximizing the minimal local freezing rate in an organ while maintaining the local thermal stresses below a specified level throughout the arbitrarily shaped and sized three-dimensional organ made of different materials has been developed. This was achieved by determining correct variation of unsteady temperature distribution on the walls of the three-dimensional freezing container. A time-accurate finite element computer program was used to predict unsteady heat conduction with phase change and thermal stresses within the realistically shaped organs. A micro-genetic algorithm was then used to achieve nonlinear constrained optimization of time-varying container wall temperature distribution so that the prescribed maximum allowable thermal stress levels are never exceeded throughout the organ.