Effects of size and number density of micro-reentrant cavities on boiling heat transfer from a silicon chip immersed in degassed and gas-dissolved FC-72

Boiling heat transfer of FC-72 from newly developed treated surfaces with micro-reentrant cavities was studied experimentally. The surface structure was fabricated on a silicon chip by use of microelectronic fabrication techniques. Four kinds of treated surfaces with the combinations of two cavity mouth diameters (about 1.6 μm and 3.1 μm) and two number densities of the micro-reentrant cavities (81 l/cm² and 96×10³ l/cm²) were tested along with a smooth surface. Experiments were conducted at the liquid subcoolings of 3 K and 25 K with degassed and gas-dissolved FC-72. While the wall superheat at boiling incipience was strongly dependent on the dissolved gas content; it was little affected by the cavity mouth diameter and the liquid subcooling. The heat transfer performance of the treated surface was considerably higher than that of the smooth surface. The highest performance was obtained with a treated surface with a larger cavity mouth diameter and a larger cavity number density. The results were compared with those for previously developed treated surfaces.