Experimental Study on Dryout Point in Vertical Narrow Annulus Under Low Flow Conditions

Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux from 26.6 to 68.8 kg/m² s and wall heat flux from 5.0 to 50.0 kW/m². The location of dryout is obtained by observing a sudden rise in surface temperature, Kutateladze correlations is cited, however proved to be not a proper one for annuli gap and modified to predict the location of dryout. Considering in detail the effects of the geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition which has a good agreement with experimental data.