Effects of presence of foreign nuclei on mass flux at cooling walls in cryogenic freezer

A cryogenic freezer system is one of the most useful systems in connection with the hydrogen isotope recovery, which is expected to be used in a fuel cycle of a D-T fusion reactor, particularly in a fuel gas refining system. As an example of the cryogenic freezer system, it is designed to freeze water vapor containing tritium at a temperature of 160 K from all condensable impurities eluted from a molecular sieve bed⁽¹⁾⁽²⁾. It is very important to investigate the influence of the variables on a mass flux at cooling walls of the freezer. The effects of frost formation on cooling walls and mist formation in a gas stream on an average mass flux in a cooling pipe were experimentally and theoretically studied and were presented in a separate paper⁽³⁾. It is considered that there are cases where foreign nuclei of impurities are present in the cryogenic freezer, because the gas eluted from the molecular sieve bed is generally composed of multi-component condensable mixtures. In this note the basic experiments and the numerical calculations were carried out for the investigation of the effects of the presence of foreign nuclei in a gas stream on the mass flux. The NaCI nuclei which are generated by the evaporation and the fast cooling-down of a NaCl solid in an electric furnace⁽⁴⁾ were used in this experiment as the foreign nuclei.