PHOTOGRAPHIC AND NUMERICAL STUDY OF BUBBLE DYNAMICS DURING NATURAL-CIRCULATION BOILING OF LIQUID NITROGEN IN A VERTICAL ANNULAR

摘要

Visualization experiments of natural-circulation boiling of liquid nitrogen are conducted in the heat flux range of 56～4085 W/m{sup}2, using a vertical annular composed of a heating core and a glass tube. The photos of bubble generation and detachment are acquired with a frequency of 2000 f/s using a high speed CCD camera. Correlations of the bubble detachment diameter and bubble detachment frequency are proposed on the base of experimental data. Then the new correlations are incorporated in the two-fluid model and two-dimensional numerical simulations are performed. Comparison of the numerical results against the experimental data demonstrated that the new correlations achieve satisfactory agreement with the experimental data.