Quenching boiling in subcooled liquid nitrogen for solidification of aqueous materials

Rapid cooling is of great importance in solidification of aqueous materials , such as in vitrification of biological cells and tissues, and in quick fr eezing of food. Quenching of samples into liquid nitrogen is a typical tech nique to obtain high cooling rate. This paper investigates the quenching bo iling of small spheres and a circular plate into saturated and subcooled li quid nitrogen. Effects of the diameters of spheres, the inclination angles of the plate, and the subcooling of liquid nitrogen on quenching boiling ar e investigated systematically. Boiling characteristics of the small spheres (representing small samples) and the circular plate (representing large sa mples) are very different from each other. The scale effect of small sample s and the inclination effect of large plate on heat transfer performance ar e obvious. The subcooling of liquid nitrogen can enhance the heat fluxes in all cases, especially in the cases of small samples. (C) 2000 Elsevier Sci ence S.A. All rights reserved.