INVESTIGATION OF THE DYNAMICS OF NUCLEATE BOILING IN SUBCOOLED FALLING LIQUID FILMS

This paper deals with the features of nucleation dynamics at boiling in falling water films at different subcooling, Reynolds number and heat fluxes. With the use of high-speed infrared and digital video the local parameters of nucleate boiling in falling liquid films such as: bubbles’ diameter before condensation, frequency of nucleation and temperature of onset of bubble appearance were received. Analysis of the experimental data showed that bubbles’ diameter before condensation has strong dependence on initial temperature and increases with the rise of heat flux. The main influence on nucleation frequency has the variation of heat flux density. At the same time the experimental data on nucleation frequency in falling water films are close to the frequency of nucleation at pool boiling. To identify the main features the comparison of received data on the local characteristics at boiling in subcooled falling liquid film with existing models for pool boiling was made.

Keywords:
boiling, falling liquid films, subcooled boiling, infrared thermography, high-speed video.
УДК 536.248

INVESTIGATION OF THE DYNAMICS OF NUCLEATE BOILING IN SUBCOOLED FALLING LIQUID FILMS