Burnout in subcooled flow boiling of water. A visual experimental study

The objective of the present work is to perform a photographic study of the burnout in highly subcooled flow boiling, in order to provide a qualitativ e description of the flow pattern under different conditions of boiling reg ime: ONE (onset of nucleate boiling), subcooled flow boiling and thermal cr isis. In particular, the flow visualisation is focused on the phenomena occ urring on the heated wall during the thermal crisis up to the physical burn out of the heater. Vapour bubble parameters are measured from flow images r ecorded, while the wall temperature is measured with an indirect method, by recording the heater elongation during all flow regimes studied. The combi nation of bubble parameters and wall temperature measurements as well as di rect observations of the flow pattern, for all flow regimes. are collected in graphs which provide a useful global point of view of boiling phenomena, especially during boiling crisis. Under these conditions, a detailed analy sis of the mechanisms leading to the critical heat flux is reported, and th e so called events sequence, from thermal crisis occurrence up to heater bu rnout, is illustrated. (C) 2000 Editions scientifiques et medicales Elsevie r SAS.