Experimental Study on Behavior of Bubbles and Temperature Fluctuation of Heat Transfer Surface by Using Heat Transfer Surface With Artificial Cavities Created by MEMS Technology

Pool nucleate boiling heat transfer experiments were performed for water using heat transfer surfaces having a unified cavity. A single cylindrical hole of 10 μm in diameter and 40 μm in depth was formed on a mirror-finished silicon wafer of 0.2 mm in thickness using the Micro-Electro Mechanical Systems (MEMS) technology. This silicon plate was used as the heat transfer surface. The back side of the heat transfer surface was heated by a semi-conductor laser beam. The back-side surface temperature was measured by a radiation thermograph with a temperature resolution of 0.08 K and a time resolution of 3 ms/line. Experiments were conducted in the range up to 1.35 × 10⁵ W/m². The standard deviations of the local fluctuating heat transfer surface temperature were calculated. So the cross-correlation coefficients between the cavity center and a certain point were calculated by using the standard deviations and the time-series surface temperature data. Then, the intensity of the thermal influence exerted by the boiling bubbles on the local position was derived. The thermal influence extents determined from the intensity were 2.1 – 3.3 times larger than the mean diameter of all departure bubbles in the present experimental range.