Numerical Simulation Of The Temperature Fields And Thermal-stress Fields In Tissue Freezing Process

Bio-heat transfer science chiefly studies the heat & mass transfer law as well as thermal effect of living tissue inside the body, and is an interdisciplinary science of biology, medical science and heat & mass transfer. In this paper, the Bio-heat transfer mechanism and force of tissue were studied with the method of interdisciplinary science on the background of researching the cure mechanism of cryosurgery. Recent years, the development of cryosurgery was remarkable for its especial advantages. But because of limiting refrigeration, temperature measurement, ice-ball inspect, the perfect progress is hard to appear breakthrough and sublimation. The aim of this paper is, chooses a reasonableheat transfer model, adopts F.E.M software ANSYS, gets transient temperature distribution and thermal stresses field of tissue in vitro, studies the influence of blood perfusion, diameter of probe and knows the mechanism damage of tissue result in thermal stresses.Adopting large F.E.M software ANSYS, using the Pennes bio-heat transfer model and validated tissue parameters simulated the freezing process of tissue in vitro, for the first time getting the transient temperature distribution under different diameter of probes and the temperature distribution on different location of tissue with the same freezing condition, and discuss the influence of blood vessel diameter, geometry structure and number. Thus the thermal analysis of blood perfusion problem in biological tissues really plays an important role in designing and conducting successful cryosurgery.Basing on the thermal analysis, the perfect elastic model was applied to analyze the thermal stresses field produced by the expansion of water and asymmetric temperature distribution by using of software ANSYS, thus gain the thermal stresses distribution on different location of tissue in the same freezing condition. In this paper, It is found that the bigger of diameter of probe, the larger of the radial tensile stress.One major task of this dissertation is to design and establish a new liquid CO2 probe experimental system. The temperature history of liquid CO2 in probe and freezing tissue can be measured and collected. Experimental test showed good agreement with the result demonstrated that computer simulation; It was clearly knowed that thermal stresses could be increase the tissue damage in cryosurgery by observing the mechanical ruptures of the freezing pork lung and liver.