Abstract
The knowledge for saturated and subcooled pool boiling CHF mechanisms is becoming increasingly important as the fundamental database for the design such as the high heat flux cooling systems using subcooled liquid pool boiling, the thermal control system of microelectronic assemblies and so on. Steady-state and transient boiling heat transfer characteristics for highly wetting liquid due to an exponentially increasing heat input with time have been investigated. Steady-state and transient critical heat fluxes (CHFs) were measured by using a 1.0 mm-diameter horizontal cylinder in a pool of highly wetting liquid such as ethanol with periods ranging from about 10 ms to 20s for wide ranges of subcooling and pressure. The transient CHFs depending on the periods were divided into two principal groups: the first one was in long period and the CHF occurred with fully developed nucleate boiling heat transfer processes, and the second one was in short period with explosive boiling heat transfer processes from non-boiling and the direct transition to film boiling occurred. The CHFs increase with an increase in subcooling at test pressures and they are independent of pressures at high subcoolings.
