The boiling performance and flow mechanism on artificial micro-cavity surfaces with different geometric parameters are presented in the present study. The test surfaces are manufactured on a 625 µm thick, 10 mm × 10 mm square silicon plate. The treated cavities are all cylinders with three diameters (200, 100 and 50 µm) and two depths (200 and 110 µm). The densities of the cavities were designed to be 33 × 33, 25 × 25 and 16 × 16 arrays with 100, 200 and 400 µm spacings, respectively. The characteristics of heat transfer for pool boiling of FC-72 on artificial micro-cavity surfaces were also examined. In this paper, visualization of the flow patterns was conducted to investigate the characteristics of the bubbles in the growth and departure process. The results indicated that boiling incipience and temperature excursion of silicon-based surfaces are more significant than those of metal-based surfaces reported in the literature. The effects of cavity density are stronger in the high heat flux region than in the low heat flux region because of the bubble/vapor coalescence near the heating surface. The heat transfer coefficient increases with heat flux and cavity density but a denser cavity will suppress the value of critical heat flux (CHF). Besides, in moderate and high heat flux regions, a larger cavity diameter surface shows earlier decay and a lower peak value of the heat transfer coefficient. The maximum value of CHF on the base area was 3 × 10 5 W m −2 (30 W m −2) for the test surface with a 33 × 33 cavity array, which is almost 2.5 times that of the plain silicon surface.
Pool boiling heat transfer phenomenon of artificial micro-cavity enhanced surfaces by wet etching MEMS fabrication immersed in a saturated dielectric fluid has been experimentally studied. The present research is to investigate pool boiling behavior including heat transfer performance and flow pattern of “artificial micro cavities” heating surfaces simulating microelectronic devices at atmospheric pressure with FC-72 as the working fluid. The test surfaces are the solid silicon based blocks with 200 μm diameter circular cavities with flat plane, 16 × 16, 25 × 25, 33 × 33 array and 50 μm depth. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (microcavities are vertical) were also investigated. Results indicated that, in general, increasing the number of micro cavities also increase the enhanced surface area and it could increase the critical heat flux. The pronounced increase of boiling heat transfer coefficients with the application of the artificial micro-cavity to the heat surface were also investigated in this paper.
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