Numerical Simulation on Freezing Phase Change Heat Transfer in Cryosurgery with Two Cryoprobes

摘要

A mathematical model for phase change heat transfer in biological tissue (including tumor and normal tissue) embedded with two cryoprobes was established. In this model, the vascular architecture was described as a tree-like branched fractal network, and the effective thermal conductivity and flow rate of blood were presented based on this fractal structure. Occurrence of three regions including frozen, phase-changing, and unfrozen regions in biological tissue during the freezing process was also considered. The numerical studies on temperature distribution and ice crystal growth process in biological tissue embedded with two cryoprobes were performed. The results showed that the growth rate of ice crystal is more rapid in the initial freezing stage and becomes slower later. So it is unreasonable to prolong freezing time merely without other assisting measures for enlarging the freezing region in the late freezing stage. Furthermore, the placement distance of the two cryoprobes plays a significant role in the growth of ice crystal in the initial freezing stage, and the influence of different distances between two probes on ice crystal growth becomes less profound with an increasing of freezing time.