Experimental investigations of nonequilibrium flashing of water in a converging-diverging nozzle

A steady water loop with well controlled flow and thermodynamic conditions was designed, built, and made operational to measure the net vapor generation rates under nonequilibrium conditions. The test section consists of a converging-diverging nozzle with 49 pressure taps and observation windows at the exit. First pressure distributions and photographic observations were recorded under various flashing conditions. The effect of the various parameters such as inlet pressure, inlet temperature, mass flux, and back pressure on the pressure distributions and flashing regimes were investigated. Under specific flashing conditions, a sharp increase in pressure (condensation shock) was observed in the diverging section (which accommodates the high back pressures). The experiments are being continued with a gamma densitometer to measure the void fraction distributions needed in the vapor generation rate calculations.