Multifractality and Universality of Thermal Fluctuations in Terrestrial and Microgravity Pool Boiling

Abstract

Nucleation site interaction in pool boiling is well known to cause intermittent bubble growth and departure. Such interactions can cause long-term temporal correlations in spatio-temporal fluctuations of temperature and heat flux and may affect the conditions leading to the onset of boiling crisis. In this study, we check for the presence of such long-term correlations. A multifractal analysis is carried out on heat flux fluctuations recorded in pool boiling experiments under terrestrial and microgravity conditions. The Hurst exponent is shown to progressively decrease as the wall temperature is increased, attaining a value close to 0.5 near the onset of boiling crisis. This trend persists for multiple pressures and levels of bulk subcooling and may serve as an indicator of proximity to the boiling crisis. Similar experiments performed with an identical setup under terrestrial gravity conditions are shown to exhibit similar trends.