Experimental investigation on the dryout point for two-phase flow boiling of steam-water at high pressures in helical coils

The dryout characteristics of flow boiling of steam-water mixtures were experimentally studied in a vertically-oriented helically-coiled tube, which was constructed of a 10 mm ID stainless steel tube with the coil diameter of 300 mm and the pitch of 50 mm. Experiments were performed in wide ranges of system pressure 8~15 MPa, mass velocity 800~1800 kg · m^-2 · s^-1 and wall heat flux 200~950 kW · m^-2. The wall temperature distribution of the helical coils in the zone where dryout occurred was obtained, and the effects of pressure, mass velocity and wall heat flux on the critical quality were systematically investigated. Based on the experimental data, a new correlation for the prediction of the critical quality of steam-water two-phase flow boiling in helical coils at high pressures was proposed.