Technical Paper
Transient Heat Transfer Experiment in Subcooled Liquid Nitrogen
1999-08-02
1999-01-2475
Cryopreservation of the biological sample usually requires rapid cooling in order to suppress the growth of intracellular ice and to reach the temperature below the vitrification temperature. The ultra-rapid cooling technique by using liquid nitrogen is favorable because it is safe, inexpensive, and harmless in most cases. This paper describes the transient heat transfer phenomena when the object is suddenly plunged into subcooled liquid nitrogen. The heat transfer coefficient in this rapid cooling process is very different from that of the steady state boiling where the quasi-static approximation is made. The cooling experiment used 0.2 mm thick copper disk. The temperature history was precisely measured during cooling process under various subcooled conditions (from 65 K to 77 K) of liquid nitrogen. The data is used not only for analyzing the cooling rate but also for estimating the instantaneous heat transfer coefficients.