Computational fluid dynamics model-based design of continuous forced convection freezing processes for human induced pluripotent stem cells considering supercooling of extracellular solutions

Abstract

This work presents a computational fluid dynamics (CFD) model-based process design of forced convection continuous freezing for human induced pluripotent stem (hiPS) cells considering supercooling of extracellular solutions. The overall model consists of a CFD model for velocity field and heat transfer calculations including the effect of the supercooling, and a cell layer model for cell survival rate calculations. Experimental temperature profiles were obtained using a forced convection-based batch freezer, and the validation of the heat transfer and solidification models was performed. The experiments were carried out by applying a 1.0 K min–1 cooling rate with an inlet velocity of 2.0 m s–1. The model was applied to three different freezer sizes with shelves containing 10, 20 and 30 rows. The applied coolant inlet velocities ranged from 0.50 m s–1 to 4.0 m s–1. It was found that the application of an inlet velocity of 3.0 m s−1 yielded an average cell survival rate of 0.934 with low survival rate heterogeneity in the freezers. This way, the freezing process for hiPS cells could be scaled to up to 170-fold compared to currently used equipment for hiPS cell freezing.