Stability of an evaporating meniscus: Part II - Experimental investigation

An experimental investigation was carried out to study the instability of an evaporating meniscus formed within a channel using three different fluids: n-pentane, iso-octane and acetone. To correlate the instability with the applied thermal load, a mathematical model was presented relating the height of a meniscus to the applied superheat. The results of this study found two different instabilities. An instability for n-pentane and iso-octane (alkanes) was found to occur for a narrow range of low heater settings of approximately 0.2 W. This instability was of a high frequency and low amplitude nature. With additional increases in heater power, this instability subsided giving way to stability. At higher heater power settings, greater than 1 W, another instability was found to occur for all three fluids. The second kind of instability had large amplitude oscillations and was persistent for heater settings beyond that of instability initiation. Given the persistent nature of the second instability, an investigation of the required superheat versus channel width revealed that each fluid required greater superheats for decreasing channel widths. Furthermore, each fluid had a different range of superheats required to destabilize the meniscus with n-pentane being the lowest and iso-octane the largest.