99/03999 Enhanced heat transfer: endless frontier, or mature and routine?: Bergles, A. E. Enhanced Heat Transfer, 1999, 6, (2–4), 79–88

Abstract

Bubble confined growth during boiling in micro-scale space is experimentally investigated. Degassed deionized water (DI water) is used to study the confined characteristics of growing bubble in microchannel. Mechanisms of bubble confinement in microscale space are discussed. Effects of heat flux and microchannel size on bubble confined growth are examined. The cross-sections of the tested rectangular microchannel are 0.5 mm × 1 mm and 1 mm × 1 mm respectively. The bubble growth process is observed and recorded by high speed CCD camera with 250 frames per second. The confined characteristics of bubble in microchannel are represented by the fluctuated variation of bubble root contact angle and other two bubble shape parameters, namely the maximal local void fraction of bubble and the bubble aspect ratio. The increased bubble growth force caused by miniaturization of space size is the chief mechanism for bubble confined characteristics in microchannel. Moreover, it is found that whether a growing bubble in microchannel will show confined characteristics is irrelevant to whether or not it will finally occupy the whole microchannel cross-section. The bubble confined characteristics are jointly controlled by the bubble growth rate and the size of microscale space. In some cases the bubble confined growth features are not displayed throughout the growth period even the bubble completely occupies the whole microchannel cross-section.