Experimental Study on Fundamental-Microscopic Mechanism of Boiling by Using MEMS Technique: Examination From Aspect of Time Series Chaos Analysis

Abstract

Pool nucleate boiling heat transfer experiments were performed for water by using well-controlled and -defined heat transfer surfaces. The cavities were formed on a mirror-finished silicon plate by utilizing Micro-Electro Mechanical Systems (MEMS) technology. Those had the exactly same cylindrical shape; 10μm in diameter and 40 μm in depth, respectively. The back side of the silicon heat transfer surface was heated by applying a Laser beam. The back side surface temperature was measured with a radiation thermometer. Bubble behavior was recorded with a high speed video camera. In the single cavity case, the reconstructed return maps from the time series data of the bubble diameter exhibited strong correlation even if the delay time was increased until 0.166 ms. It was suggested that the bubble diameter from the single cavity can be predicted deterministically over long time period. In the triple cavity case, when the cavity spacing was narrow, the bubbles frequently coalesce to the bubbles generating from neighboring cavities. When the cavity spacing became wide, the bubbles coalescence was suppressed. The reconstructed return maps of the bubble diameter indicated that when the cavity spacings ≤ 3 mm, the bubble diameter after a few m seconds could not be predicted. This loss of the predictability for the bubble diameter was caused by the interaction/coalescence from the neighboring cavities. The three-dimensional reconstructed attractors of the surface temperature of the cavity position were examined. The attractors of the single cavity case and the triple cavities with S = 4 mm case were quite similar and like a ball. This suggested that when S ≥ 4 mm, the interaction between cavities disappeared and the chaotic complexity might not appear in the surface temperature variation. When S = 1 ∼ 3 mm, the attractors were conical and the chaotic complexity might exist.