ISSN Online: 2377-424X
ISBN Print: 0-89116-299-2
International Heat Transfer Conference 7
BOILING CRISIS IN RESTRICTED GEOMETRIES WITH A NEAR-BY COOLED WALL
Résumé
The effect on the critical heat flux in water of restricted space or the presence of cooled walls in the vicinity of the heater surface is investigated. Such designs appear frequently in many practical constructions, such as in the nuclear industry for instance. The chosen geometry is here a typical vertically placed stagnant water annul us, limited by an inner heated wall and an outer cooled sleeve. Gap widths range from 1 to 16 mm. A detailed temperature instrumentation records the temperature gradient in the annular water gap. Tests conducted at constant pressure for different cooling water temperatures show a strong effect of the cooled wall. The boiling process is here clearly subcooled with large radial mass transport from one wall to the other, particularly when the crisis is approached. This radially directed transfer with subcooled characteristics explains the heat flux values observed in some cases, where classical analysis using widely used correlations predict much lower or much higher limits.