Abstract
In this study, the steady-state and transient critical heat fluxes (CHFs) were measured on 1.0 mm diameter horizontal cylinders of gold and platinum heaters under saturated conditions due to transient heat inputs, Q0exp(t/τ), in a pool of Fluorinert FC-72. Heaters were heated by electric current with the periods, τ, were ranged from 10 ms to 20 s, and the pressures ranging from atmospheric up to around 1.2 MPa. The steady-state CHFs are dependent on pressure and almost agree with the values obtained by Kutateladze's correlation based on hydrodynamic instability (HI) model. It was considered that the boiling inception and the direct transition during the steady-state period occur by the pre-pressure of = 1.2 MPa. The trend of typical transient CHFs were clearly divided into the first, second, and third groups for long, short, and intermediate periods, respectively. The direct transition process to film boiling without nucleate boiling for the short period was confirmed due to the heterogeneous spontaneous nucleation (HSN) in originally flooded cavities on the cylinder surface. It was observed that the CHFs for direct transition process during short periods show a difference in the dependency of pressures between both heaters.
