A finite element model for phase change heat transfer in a composite tissue with blood perfusion

This paper describes a finite element model of the thermal response of a human to extreme subfreezing environments and the transient temperature fields that are produced at specific locations within the body. This analysis includes the effects of latent heat of fusion from the liquid to the solid phase and of blood perfusion in selected tissues during the freezing process. A highly simplified physiological model is assumed. This type of analysis can be used as a predictive tool in many applications such as cryosurgery and cryopreservation of organs. The finite element model described herein has many advantages over standard numerical techniques such as finite difference methods for analyzing heat transfer problems. This method can treat very general geometries with many different tissue types, each having unique thermal properties, and unique blood perfusion and metabolic rates. This model can incorporate either convective thermal resistance at the body surface or a prescribed temperature history as a boundary condition, either of which may vary as a function of time or temperature. This analysis extends previous work by incorporating the effects of latent heat and by including a blood perfusion rate that varies with temperature in individual tissues.