Numerical Simulation on Phase Change Heat Transfer Process of Biological Tissue in Cryosurgery

Objective To study the mechanism of heat transfer by simulating a complete freezing-thawing process of biological tissue.Methods A numerical model of phase change heat transfer in biological tissue was developed with consideration of the difference of thermophysical properties for normal biological tissue and tumor.The biological tissue was assumed as a porous media.The different thermophysical properties between tissue framework and tissue fluid(as water in tissue,etc) were considered.An apparent heat capacity method was applied to solve the phase change heat transfer problem.Results It was showed that the temperature of biological tissue decreased more quickly during the freezing process when the initial cryoprobe temperature was lower and the cooling-rate of cryoprobe was faster.The temperature of biological tissue increased more quickly with faster warming-rate of cryoprobe in the thawing process.It was also showed that the porosity,blood perfusion rate and metabolic heat generation of the biological tissue had effects on tissue freezing temperature in biological tissue.Conclusion To study the thermal process of biological tissue in cryosurgery will be very helpful for further application in cryosurgery.