ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
HEAT TRANSFER ANALYSIS FOR COOLING PROCESS OF LIQUID NITROGEN UTILIZING THIN FILM EVAPORATION
Resumo
Vitrification is one of effective methods for cell cryopreservation. An ultra-fast cooling rate is beneficial to
improve the vitrification level of the extra and intracellular solution and decrease the concentration of
cryoprotectant. A novel ultra-fast cooling method utilizing thin film evaporation was developed. In it, a
frozen carrier with a microstructured layer was produced. Liquid nitrogen, serving as the working fluid, was
dispersed into the microstructured layer by capillary force, and evaporated at a high speed. Due to this quick
evaporation and heat absorption, the frozen carrier was ultra-fast cooled. This study analyzed the transient
heat transfer of this cooling method by experiments and numerical simulations and optimized it to achieve
higher cooling rate. The numerical results were agreed with the corresponding experimental data very well.
The results showed that the evaporation heat transfer of liquid nitrogen is the key factor. Enhancing the thin
film evaporation of liquid nitrogen by optimizing the morphology of the microstructured surface can
improve the cooling rate obviously. The temperature distribution within the frozen carrier is almost
homogeneous in the whole cooling process because the conductive thermal resistance within the carrier is
obviously lower than that of the liquid nitrogen evaporation on the surface of the frozen carrier. This ensures
that all of cells in the suspension can achieve the same cooling rate in the whole frozen process. The current
investigation will support better the development of the novel vitrification method.