School of Mechanical Engineering, KIIT Deemed To Be University, Bhubaneswar, Odisha 751024, India.
School of Mechanical Engineering, KIIT Deemed To Be University, Bhubaneswar, Odisha 751024, India.
J Therm Biol. 2019 Apr;81:146-153. doi: 10.1016/j.jtherbio.2019.03.001. Epub 2019 Mar 5.
Cryopreservation is the method of preservation of biological tissues for future references without causing significant damages to their physical and functional properties. This can be done by exposing them to very low cryogenic temperature that involves a greater heat removal rate. A two dimensional numerical model is developed to study the temperature distribution, cooling rate attained and movement of the freezing front during the cryopreservation process. The Pennes Bio-heat model is used for current study. The Finite Volume Method is employed for discretization of the governing differential equations while the Tri-Diagonal Matrix Algorithm is used to solve the discretized algebraic equations to find temperature distribution inside the domain. The Enthalpy-Porosity method is used to track the solid-liquid interfaces during the freezing process. The current model is first validated with the result of the existing literature. In the present work, freezing of tissue is done from one and two sides in two separate cases and the resulting temperature distribution inside the tissue and cooling rate in the two cases are compared. It is found that the freezing rate of tissue is enhanced about two times when it is freezed from two sides as compared to freezing from single side. Further, it is observed that a lower value of blood perfusion rate causes a lower value of the final temperature of the tissue after freezing. Thus, it can be concluded that the tissue with high blood perfusion rate is to be freezed in a lower cooling medium temperature. In the present condition, metabolic heat generation plays no significant role in the temperature distribution inside the healthy tissue.
冷冻保存是一种将生物组织保存以备将来参考的方法，同时不会对其物理和功能特性造成重大损害。这可以通过将它们暴露在非常低的低温下实现，这涉及到更高的热去除率。本文开发了一个二维数值模型来研究冷冻保存过程中的温度分布、达到的冷却速率和冻结前沿的移动。当前的研究使用了彭内斯生物传热模型。有限体积法用于离散控制微分方程，而三对角矩阵算法用于求解离散化的代数方程以找到域内的温度分布。焓-孔隙率法用于跟踪冻结过程中的固液界面。当前的模型首先与现有文献的结果进行了验证。在本工作中，组织从一侧和两侧在两种不同的情况下进行冻结，比较了两种情况下组织内的温度分布和冷却速率。结果发现，与从单侧冻结相比，从两侧冻结时组织的冻结速率提高了约两倍。此外，还观察到较低的血液灌注率导致冷冻后组织的最终温度较低。因此，可以得出结论，具有高血液灌注率的组织应该在较低的冷却介质温度下进行冷冻。在当前的条件下，代谢热生成在健康组织内的温度分布中没有起到显著的作用。
