Boiling driven mixed convection in a L-shaped slab geometry

The behaviour of a two-phase mixed convection loop with subcooled boiling h as been investigated in order to design a passive cooling system. In a test facility with a L-shaped slab geometry subcooled water is pumped into the horizontal lower duct and heated up by the hot bottom plate. Vapour bubbles generated at the heated wall establish a disperse two-phase region with co nsiderable void, measured by a gamma densitometer. The structure and stabil ity of the two-phase mixed convection can be characterised by the Phase Cha nge Number and the Subcooling Number. Operation regimes with flashing induc ed instabilities in the chimney are indicated in the stability diagram. For the numerical simulation the Eulerian two-fluid-model in the commercial so ftware package CFX4 has been used. The two-fluid-model had to be extended w ith physical models for bubble generation under subcooled boiling in the lo wer duct and for water-bubble interfacial forces in the chimney, which have been validated by data of a bubbly flow experiment and of a boiling experi ment.