Unsteady Dispersed Flow Heat Transfer Under Loss-of-Coolant Accident Related Conditions

Heat transfer from a heated tube to an unsteady dispersed flow was studied experimentally at post-dryout conditions for the following range of variables: mass flux, 1. 40 to 3.60 g/cm^2. s; pressure, 1.20 to 1.60 bar; heat flux, 1.70 to 4.20 W/cm²; inlet quality, 0.50 to 1.0; flow cycle, 0 to 3 s⁻¹. The experimental results show that at equivalent mean vapor quality no noticeable differences in the heat transfer data exist between a steady-state and a cyclically dispersed flow. A comparison of the experimental data with the wall temperature calculated using an analytical model indicates that the interphase heat transfer is of considerable importance and that the wall-droplet interaction can be neglected at qualities greater than 0.50.