Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
COMPARATIVE ANALYSIS OF VITRIFICATION TECHNIQUES WITH SLUSH NITROGEN AND LIQUID NITROGEN USING NUMERIC SIMULATIONS (CFD)
Submission Author:
Massoxi Cuiêca , RS , Angola
Co-Authors:
Massoxi Cuiêca, Mario Henrique Macagnan, Jacqueline Copetti, Álisson Renan Stochero da Silva, Guilherme Steffenon
Presenter: Massoxi Cuiêca
doi://10.26678/ABCM.COBEM2021.COB2021-1239
Abstract
In biology, the cryopreservation studies the low temperatures effect in the cells, tissues and living organisms, aiming to preserve the composition of cells for longs periods. These techniques of high complexity are constantly improving due to their wide clinical applicability. Several studies have been conducted so that these procedures can offer good results in the process of freezing and thawing human ovarian tissue, sperm, embryos and other biological materials. Within cryopreservation processes, vitrification is an alternative to the conventional slow freezing method due to the high cooling rates. Associated with the procedure, a factor that confers a higher probability of survival of biological material, because less concentrated cryoprotectors are needed, reducing the toxicity potential in the samples, and avoiding the formation of ice crystals that can cause injury in the samples. In general, the conventional vitrification procedure consists of dipping the samples directly into liquid nitrogen (LN), obtaining cooling rates of 2,500 ºC/min compared to 1 to 10 ºC/min observed in slow freezing. The main obstruction to further increase the cooling rate is associated with the Leidenfrost effect, a factor that negatively affects the heat transfer coefficient between the sample surface and liquid nitrogen due to the formation of a "vapor blanket" around the sample. However, the removal of this blanket is critical to further improve the cooling rate in the vitrification processes. Recent studies with slush nitrogen (SN) showed satisfactory results, not being observed "vapor blanket" formation around the sample, but the effects associated with heat transfer were not analyzed. Therefore, this work aims to compare two techniques of vitrification, slush nitrogen and liquid nitrogen, through computational modeling (CFD), with purpose of analyzing the main factors associated with heat transfer, such as cooling rate curves, temperature contour lines during solidification, heat transfer coefficient, and other parameters. Numerical simulations (CFD) of the vitrification protocol were performed using the commercial software ANSYS Fluent.
Keywords
Heat transfer, Slush Nitrogen, Cryopreservation, Thin Film Evaporation, Computational Fluid Dynamics - CFD, Vitrification Process
