Estudo da evaporação de filme fino de nitrogênio: uma metodologia de vitrificação para criopreservação de material biológico

Abstract

Cell cryopreservation is a branch of science that describes methodologies to preserve living cells through freezing and conservation at negative temperatures. With this in mind, some researchers study the process of cellular freezing in the most different ways, and it can be classified between slow and fast freezing (vitrification). So the present work aims to experimentally study the method of vitrification by thin film evaporation of nitrogen for cellular cryopreservation. This study has an experimental comparison between the thin film evaporation method and the immersion method, using liquid nitrogen as coolant and water as a sample in both cases. The experimental study used different test sections, with different dimensions and compositions, in order to identify the best layout to optimize the cooling rate. In addition to the experimental study, the work also developed a numerical methodology to describe the process studied through computer simulations in CFD using Ansys Fluent ® software. The numerical simulation studied considered a 2D geometry, using k-ω turbulence method and solidification method to simulate all the processes that occur in thin film evaporation. The experimental results showed a higher freezing rate in the immersion methods, presenting values of approximately 900°C/min. The thin film evaporation method, in the best case studied, found a freezing rate of 500 °C/min. Finally, the numerical simulation was also able to predict the beginning of the freezing process, demonstrating the nitrogen flow profiles, temperature variation and the solidification process of the sample.